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Color Photography - Autotype Trichrome Carbro

( Originally Published 1938 )



THIS is a method of making natural color prints on paper by means of superimposed red, blue and yellow pigment images which are formed by chemical reaction from the silver images of black and white bromide prints which have been made from separation negatives.

The ultimate aim of every photographer is to be able to produce natural color prints on paper in what-ever Size is desired. Autotype Trichrome Carbro is used by practically all leading color workers for this purpose. Prints are regularly made in sizes as large as 16 by 20. Before giving detailed instructions on this process may I say that only those who are willing to adhere strictly to the details and to make a careful study of uniform requirements necessary for success, should attempt it. If you are already experienced in the making of color separation negatives you are ready to proceed. If not you must, of course, first learn to make the separation negativeS, instructions for which you will find in a previous chapter.

In order to keep the subject well in hand and to follow closely from one operation to another we are going to take you through a particular procedure which, while it may not be the exact routine of many color workers, will, if followed closely, give satisfactory color prints. Later, we will enumerate variations and alternate methods of procedure.

MATERIAL NEEDED.-This layout is figured for a commercial photographer who wishes to make 11 by 14 or larger prints. For experimental work smaller sizes or quantities will do.

I roll of bromide paper from which you can cut sheets with grain all one way to avoid unequal stretch, or cut sheets ordered specially from your dealer with grain cut one way. Use only a matte bromide paper which does not have an overcoating of gelatin above the emulsion. Illingsworth DeLuxe Matte Normal, Carbro Bromide is made especially for Carbro.

1 band (roll) each Autotype triclirome carbon tissues, blue, red and yellow.

1 band Autotype temporary soluble support.

1 band Autotype white single transfer paper, single or double weight as preferred.

3 or more sheets 16 by 20—50/1000 clear temporary transparent supports (celluloids). Nitrate base.

1 bottle Carbro waxing solution.

1 heavy duty flat rubber squeegee, 15 to 18 inches.

2 sheets plate glass about 18 by 22. Several yards bleached cheesecloth.

8 ounces pure rectified spirits of turpentine. 8 ounces benzol (or naphtha).

1 dairy type glass enclosed thermometer.

Several yards copper wire about No. 14, cut in 20-inch lengths.

12 sheets heavy wax paper about 24 by 36.

1 timer for measuring seconds and minutes.

In addition to the above you will need such items as

U. S. photo clips
Enamel trays
Graduates
Blotters, World 140 lb.
Absorbent cotton, etc.
Columbian spirits (wood alcohol 95%)

You may use items which you already have, provided they are absolutely clean and the enamel of the trays used is not chipped.

CHEMICALS.—YOU may purchase for your initial experiments prepared Carbro sensitizing solutions sold under the label of Trichrome Carbro solutions, A and B.

SENSITIZERS.—If you wish to make your own sensitizer you will need the chemicals called for in the formulas which are given below. Buy the chromic acid in small containers, ounces or quarter pounds to keep it fresh. All chemicals should be of the best grade C.

Use a sufficient amount of each of these baths to cover well the size of pigment paper used, in order to insure even action in the sensitizer. The No. I bath may be used for several prints, but No. 2 bath should be renewed for each set, as it is altered by the No. I solution carried over into it. These baths should be used at a temperature of 60° to 65 ° F. (15 ° to 18 ° C.).

MAKING THE BROMIDES.—Next to the negatives, the making of the bromides is the most important step. Your success in Trichrome Carbro depends on the care you use in making the bromide prints. Contrasty bromides are as unsatisfactory as contrasty negatives. Do not hurry over the bromides. Study them well. Time spent here will be well repaid later.

You will find a condensing lens system with a rheostat control very useful for making Trichrome Carbro bromides. You can increase the contrast of the negative by using a Mazda bulb and no diffusing glass or lessen it by using a frosted bulb or by interposing a sheet of ground glass back of the condensers near the light source. Photofloods are not satisfactory for this work, as they change quickly in light value. The rheostat control on your light enables you to regulate the strength of the light so that an average exposure can be maintained. Do not stop down very much when enlarging, as you will interfere with the light rays and cause uneven illumination.

Be sure the light area on the easel is even. First focus with the negative in place in the carrier, then remove the negative and examine carefully the light space. This should be clear and even. Moving the light source back and forth, up and down, or right to left should remedy any uneven or colored edges. Most books on optics show how this is done.

Note: Do not attempt to dodge bromides in printing for color except, perhaps, where a background is to be faked. Do the necessary retouching, if any, on the negative. Retouching should be attempted only after a first color proof has been made and then only by carefully considering the color action on all three negatives. A dodging medium which can be removed, if not suitable, is best for holding back parts which call for correction. Check the focus again on the easel after you have stopped down. Avoid small stops. You are actually projecting one fiat surface on to another and do not need to increase the depth by stopping down. Decreasing of illumination is best accomplished by diffusing the light source with glass or rheostat control.

Cooper Hewitt mercury vapor M tubes as a light source give a softer bromide than the Mazda illumination.

Start with the blue printer negative, that is, the one that was made through the red filter.

Note just how you place the negative in the camera, that is, right to left, top or bottom, and arrange a guide by tracing, with a blue grease pencil, the outline of the first negative of the set, on the easel, so that the next negative can be placed in the same position. This is a convenient time saver, particularly if you are using negatives of a smaller size than the regular carrier calls for. Make provisions for a white border 1/2 to 3/4 incheS wide.

For the development of bromides for Trichrome Carbro most workers prefer amidol, although many workers use Eastman D-72 or D-64, formulas for which are included in this chapter. Any similar amidol or metol-hydrochinone developer formulas given by the manufacturer for their papers may be used if the bromide prints developed in them meet the requirements for Carbro.

Place a test strip of bromide paper on the easel so that it covers the strongest highlight (whitest part) of the subject and also the grey scale.

Make several test prints until you find an exposure and developer strength which will give with one and a half to two minutes development at 65° F. (18' C.) a slight grey tint in the strongest highlight and at the same time retain as many steps as possible in the grey scale.

If the grey scale in each negative is matched perfectly, the remaining prints can be exposed and developed so that their respective grey scales in the bromide match those of the blue printer bromide. If, however, as is frequently the case, the grey scales do not exactly match, or if no scale has been included in the subject, one muSt be guided by and match the white and neutral tones of the red and yellow printer negative with the print of the blue printer, the depth of which you have already decided.

Note: At this point, knowing the colors of the subject, study the appearance of the bromides. The strength of the color in your finished print will be directly in proportion to the density of the silver bromide image.

A black object will, of course, have a fairly heavily developed silver image on each bromide, as a deposit of the three pigment colors (red, blue and yellow) will yield a black, whereas a green object will have dark areas in proportion to its shade in the blue and yellow printer bromides. Upon the face of a portrait the blue printer as a rule will have only dark areas in the lips, eyes and hair, whereas in the red and yellow printer bromides there will be more or less density according to the complexion, etc. Keep negatives carefully marked. In some subjects the red and yellow printer negatives resemble each other so closely that the worker may by error print them in the wrong color if they are not carefully marked.

Develop each print separately to avoid abrasion marks on the emulsion surface. Use developer for only one or two sets made at the same time. In larger sizes use just enough for three prints and replace for next set. Keep temperature uniform.

Keep a record on the back of each print of paper used, exposure time, stop, printing color, development, etc., for later study and comparison.

A pencil or narrow strip of black card laid beside the grey scale image during exposure will give you a Strip of pure white for comparison when developing.

Insert prints evenly and carefully into developer, as any uneven start in developing, while apparently over-come in the full development, may show up later in the Carbro image. One cannot emphasize too much the necessity for cleanliness at this point. Any stains or spotS on the face of the print will prevent the later chemical reaction of Carbro solutions.

After development, rinse in plain water or acid short stop and fix.

Do not use a fixing bath containing alum.

Washing should be thorough—thirty-five minutes in running water, or about ten changes if washed in still water in trays.

When washed, lay face up on a clean glass, wipe face with damp cotton swab, and hang by clip to dry. Prints larger than 11 by 14 should be dried face up at an angle on clean blotters. Prints dried level, face up, are apt to have water rings from uneven drying, which will show in the finished Carbro. Most workers dry the prints before making the Carbro, but there is no reason why they cannot be used while still wet.

In drying prints by hanging on clips suspended from a line, have clips hanging free—that is, not gripping the print and line at the same time.

Prints may also be dried face down on frames covered with clean (stretched) bleached muslin. Do not dry Carbro bromides between blotters, as they will stick because of the unhardened gelatin surface.

Be sure that no grease or dirt comes in contact with the face of your print. Remember this is now your printer and its surface must be treated the same as a wet negative. In most localities, lime in the water makes it necessary to swab the surface of the prints after washing with a z per cent to 3 per cent solution of acetic acid, after which they are rinsed in tap, or, if possible, distilled water.

Where it is necessary to use this acid rinse, the bromide prints should be developed a little heavier.

Make two setS of bromides of each subject, one a little darker than the other, until you determine just the right depth. This will save time if you find it necessary to make a lighter or darker Carbro of any particular color.

DEVELOPERS.—Amidol and Eastman D-72 are favorite developers with color workers. Suitable formulas are given below.

AMIDOL DEVELOPER

Water 20oz. 590 ccm
Sodium sulphite (dry) 1 1/2 oz. 42.5g
Potassium bromide 10gr. 0.7g

When dissolved add fifty grains (3 g) amidol. This developer will keep only two or three days. Make up fresh as needed. Develop one and a half to two minutes at 65° F. (18° C.).

Dissolve the chemicals in the order given. For bromide paper use stock solution one part, water four parts. If higher contrast is desired with bromide paper use stock solution one part, water two parts, or stock solution one part, water one part. With the one to one dilution, add fifteen grains of potassium bromide per 32 ounces of developer (one gram per liter).

If you find you cannot retain all the steps in the grey scale try Eastman D-64, a variable contrast developer.

To each 32 ounces (1 liter) of developer (A, B or C) dilution, ready to use, add one dram (4 ccm) of 10 per cent potassium bromide solution.

Develop not less than one and a half minutes at 700 F. (21° C.).

FIXING BATH FORMULA.—The fixing bath must be plain hypo with potassium metabisulphite (alum must not be used as this hardens the emulsion and blocks chemical action).

Allow hypo to become cold, then slowly pour No. 2 into No. 1, stirring rapidly.

Time each print and remove them from the fixing bath after fifteen minutes. Do not allow any one bromide to stay in the fixing bath longer than fifteen to twenty minutes. As soon as fixed, remove it at once to the washing tray.

With the bromides made, other preparations are in order.

PREPARING THE TRANSPARENT SUPPORTS.—Clip one corner of each celluloid on the shortest side to identify which side is waxed. Keep this corner at the top and right when waxing. Punch holes about % inch in diameter along both ends and sides of celluloids about three inches apart. (The use for these will be explained later.)

When the celluloids are used for the first or second time they must be scrubbed well with a gritless soap powder such as Gold Dust or Bon Ami. This cleans and gives a slight tooth to the surface on which to develop the pigment image. After each regular use the celluloids should be cleaned with soap and warm (not hot) water before being again waxed.

WAXING.—Prepare a round pad by folding several small pieces of flannel into a larger one and tying around the top with a string. Keep this in a container away from dust when not in use. Shake some of the waxing solution on the flannel pad and apply to the surface of the celluloid support. Cover the entire surface with a thin layer of the solution. Wipe this off with a clean flannel or cheesecloth, then set aside and immediately wax the other two. By this time the first one will have set a little. Each celluloid is now polished five or ten seconds with a circular, firm pressure, the same as you would use to polish a squeegee plate. Do not leave uneven or heavy wax areas.

When waxing is complete the celluloids are ready for use.

Note: Other methods of waxing and formulas will be given later.

While under normal workroom conditions where the temperature does not exceed 70° F. (20° C.) and the humidity runs 60, Trichrome Carbro pigments can be mounted directly on to the celluloid when stripped from the bromide print, it is just possible that under very hot, humid conditions it may be necessary to immerse the pigment, when stripped from the bromide, for one minute in a bath of Columbian spirits (good grade of wood alcohol) to remove excess moisture before mounting on the celluloid. This, however, should not be necessary under normal circumstances.

Another method used is to prepare the celluloids with an albumen coating which is put on above the wax to give the pigment a good tooth. We give below the formula for this method in case it should be necessary under adverse conditions.

ALBUMEN SUBSTRATUM FORMULA.—Beat the white of one egg to a froth and add fifteen ounces (450 ccm) cold water. Dissolve 150 grains (9.7 g) potassium bichromate in five ounces (150 ccm) of warm water and add to the egg and water. Mix well and filter twice through cheesecloth. Powdered egg albumen may be used in place of the white of egg, shaking one-half oz. (15 gr.) into fifteen ounces (450 ccm) of water and adding the bichromate and water as given above. This solution, stored in a dark bottle, can be used repeatedly until it becomes smelly, when it should be replaced.

One of the partially (or fully) dried waxed celluloids is placed in a tray of the albumen solution, covered well and rocked for about one minute.

It is then drained and set aside upright for a moment while the next celluloid is placed in the solution. The first one is then rinsed by shaking face up about fifteen seconds in a tray of cold water and set aside. As soon as all the celluloids are treated in this way they are hung up in daylight or strong artificial light to dry. Drying in the strong light makes the thin layer of albumen left on the celluloids insoluble and giveS a practically frill-proof layer on which to develop the pigment images.

SENSITIZING AND BLEACHING.—From the stock solution A, prepare, in the proportion given, a sufficient amount of solution to thoroughly cover the sheets of pigment paper. This iS known as working bath No. I.

From the B stock solution prepare a more generous portion, to be known as working bath No. z. The No. I bath can be used for two or three sets. The No. 2 bath should be discarded after each set. Arrange these baths on a work table from left to right. (See data on standard temperature controlled workroom later.)

The temperature of the solutions must be about 60° F. (i6° C.), not over 65° F. (18° C.). The work-room should be cold and fairly dry. Temperature 65° F. (08° C.) to 70° F. (20° C.) and humidity between 50 and 60. If the bromides have been dried, place them in a tray of cold water for ten to fifteen minutes before starting, so that they will have time to expand fully and evenly.

Cut one sheet each of red, blue and yellow Carbro pigment tissues about an inch larger all around than the print (in small sizes less margin will do). Set up on work table, preferably over a sink or grating, the /" or thicker plate glass and arrange your flat rubber squeegee handy at the upper right-hand corner.

Immerse the first color (working always in the particular order of blue, red and yellow) in the No. I bath, noting the time from a second and minute-hand clock hanging near by. The exact time in this bath is not important, provided all the colors are handled identically under the same temperature and humidity conditions, the object being to saturate the pigmented gelatin with the solution. This, as a rule, takes two minutes at 60° F. (i6° C.), or less if warmer. Most workers leave it face down for one minute and face up for the second minute. It usually takes about one minute for the pigment to become limp enough to reverse face up. When you first put the pigment sheet in the solution, rub your hand over the back to remove air-bells and permit even absorption.

During the last minute that the pigment is soaking in the No. 1 bath rinse your hands, go to the tray in which the bromides are soaking and pick up the corresponding bromide, in this case the one marked "blue"; place it face up on the plate glass, which should be clean and level, run over it with a clean flat rubber squeegee to place it in position, wipe the face with a damp, clean cotton swab, and pour a generous pool of cold water over it so that the water lies well above the prints. Be sure that no part of the print is left uncovered.

Return to the pigment, which has now completed its two minutes in the No. 1 bath. Lift it up and let it drain about five seconds, and immerse it face down quickly and evenly in the No. 2 bath.

The time in this bath determines the contrast and density of color in the final Carbro. The usual time iS twenty to thirty seconds, according to the density of the bromide. A few trials will soon determine the proper time for your type of bromides, temperature of solutions, etc. The shorter the immersion, the darker and more contrasty the result, and vice versa. This time is noted by carefully watching the second hand of the clock. Keep a record of the time of all operations for future comparison.

At the end of the period decided on, lift quickly, and without loss of more than two or three seconds, lay the pigment face down upon the face of the bromide print (which is covered with a pool of water), allowing the pigment to extend over the edges of the bromide print. The pool of water enables you to place the pigment in the right position before the chemical action begins and also insures even bleaching. As soon as the pigment is in position, pick up the flat squeegee with the right hand, holding the left end of the pigment with the fingers and thumb of the left hand, and draw the squeegee quickly and evenly with fairly firm pressure from left to right, without allowing the pigment to slip. Slipping after squeegeeing is started will give a double image.

Note: A useful guide in placing the pigment quickly in the proper position can be made by making a square on the glass at the left with 1-inch adhesive tape. Put the print flush with the inside of the square. The pigment of the proper size can then be dropped quickly along the left outside of the square with the assurance that the pigment will fully cover the bromide at the right and top.

Reverse the hands and the squeegee and draw the squeegee from right to left with the left hand. Now go back and forth several times with even pressure to insure good contact between the pigment and bromide paper. Use a squeegee with a short rubber, which will give even pressure, rather than one with long lip which will bend under the stroke of the squeegee. Wipe the squeegee on an old towel after each stroke. Always use the same type and direction of stroke for uniformity in pressure and stretch on the pigment gelatin. Wipe off the back of the pigment with a dry cloth.

Pick up with pen-knife point by digging under pigment and bromide so as not to separate. Lay bromide, print side up, on a folded lintless blotter (140-lb. World is best). Place a sheet of wax paper above sandwich, fold down top section of the blotter and run over out-side of blotter fold with a print roller several times in one direction with fair pressure. The entire procedure from the beginning of the sensitizing to this point will, with a little practice, take just five minutes. Turn the minute hand of the clock back to zero.

Note: We must pause here to impress upon you that the time between lifting the pigment from the No. 2 bath and squeegeeing it upon the bromide is the most important and critical time of the entire process. Any hesitation in placing the pigment upon the bromide in effect increases the time of the No. 2 bath. Delay or uneven squeegeeing after it is placed on the bromide may give uneven markings. Close contact is essential for sharp, even-toned prints.

Leave the blue pigment and bromide under the blotters or glass for the moment, and repeat the procedure with the remaining red and yellow pigments and their respective bromides.

When you have completed the red and yellow and have them safely between the blotters, the minute hand of the clock will be at ten, showing an elapsed time of ten minutes since you placed the first (blue) pigment and bromide together.

The exact length of time the pigment and bromide are left in contact (or as we call it bleaching) is also not critical, the necessity being that it shall be left long enough for the silver in the print to set up the maximum insolubility in the bichromated pigment. This will be accomplished in more or less time according to the temperature of the workroom.

Some workers find that five minutes is sufficient, ten is not harmful, and fifteen is a handy time when one is working alone. Be sure that they are all left the same length of time, to keep the physical condition of the gelatin the same. Too long contact may cause insolubility; too short, frilling. Leaving them fifteen minutes gives you time to prepare for the next step.

MOUNTING THE PIGMENTS ON THE CELLULOIDS.-At the end of fifteen minutes slide one of the waxed celluloids into a tray of cold water, wax side up. In cold weather water should be drawn in advance and allowed to set to expel air from water, otherwise tiny air-bells will cause white spots in print.

Remove the blue pigment and bromide from between the blotters. If the pigment is much larger than the bromide print, lay the two, print side up, on a clean glass and with a safety razor blade or sharp penknife trim off the surplus pigment to within about 1/4 inch of the print. This will save time later in the development.

Now separate the print and pigment. Drop the bromide print in a tray of water face down (we will come back to it later).

Slide the pigment with the blue image down into the water and take it out together with the celluloid, being sure that you have covered the face of the pigment fully with cold water. Place on squeegee board and squeegee firmly in both directions, wiping off the back of the pigment and celluloid margins with a dry cloth.

If, in warm, humid weather the pigment sticks to the bromide print, slide the bromide and pigment together into a tray of cold water and separate them under water, after which the pigment is mounted on to the celluloid as usual. Look at the back of the celluloid to see that there are no air-bells. Pick up the celluloid with pigment and place it between blotters. Go over moderately firmly with a print roller to insure even moisture, and place under bottom of blotter stack or glass.

Repeat this handling with the red and yellow pigments. By the time you have completed up to this point with the yellow pigment, the blue will be about ready to develop. Ten to fifteen minutes on the celluloids (according to temperature and humidity) is the usual time.

Now you have a few minutes to spare. Give the bleached bromide prints a few changes of water and put them to wash in running water. Do not let the water fall directly on them as this may cause blisters. Later, after washing thoroughly, redevelop (but do not fix) in a weak, regular metol-hydrochinone developer. (Do not use amidol for redeveloping, as it is apt to stain.) These prints can be used over again. In actual practice, however, few workers use the bromides a second time. If the bromides blister when redeveloped, try drying them first and redevelop later.

DEVELOPMENT OF THE PIGMENTS.—NOW prepare a generous tray of warm water (temperature about 105 F. (40° C.) to develop the blue carbro image. Slide the celluloid containing the blue pigment into the tray of hot water face up. In a few seconds the color will begin to ooze out around the edges. If it does not begin to ooze in ten seconds, run the tip of your finger lightly around the four sides, whereupon you should see dark blue lines, which is an indication that the upper layer of the pigment has softened sufficiently to strip off the top or paper covering. Do this from one end to the other, being careful that the last edge of the paper does not back-swipe and mar the pigment image. Discard the paper backing.

Shake the celluloid vigorously by first one corner, then the other, for a few seconds; then grasp the two ends of the celluloid and slide back and forth face up in the water until the color has cleared away entirely, leaving a clean image from which the blue color no longer runs. Then rinse in a fresh tray of warm water for a few seconds, after which it is chilled in a tray of cold water and hung up to dry.

A good test at this point is to have a piece of white celluloid on which to drain the last few drops to see if they contain any more color. As soon as the images begin to set, drying can be hastened by blowing air lightly with an electric fan. (See note on drying.) Repeat the same operation with the red and yellow, standardizing as nearly as possible the time of the drying between the blotters.

TEMPORARY SOLUBLE SUPPORT.—YOU are now ready to register the three pigment images onto the temporary soluble support. Cut a piece of temporary soluble support from a roll, a little larger than the print, and soak for five minutes in a tray of water at 70° F. (° C.). The temperature is important. If soaked in water too cold the gelatin will not become soft enough to pick up evenly the entire image. At the end of five minutes transfer to a deep tray of cold water about 65 ° F. (18° C.) and slide the celluloid with the blue image into the water under the temporary soluble support, which, of course, is gelatin side down. Draw the two out carefully from the water to avoid air bubbles. Slide the paper around so that you have a margin of white all around. Lay paper side up on the squeegee board and squeegee firmly from right to left into contact. Place between blotters and run moderately firmly with a roller squeegee. Remove at once and dry celluloid off with a clean cloth and also wipe carefully the paper backing, particularly around the edges.

It can now be placed in a gentle current of air in a warm room or drying cabinet. When dry, the soluble support paper will leave, or it may be stripped from the celluloid, bringing with it the entire blue image. (The celluloid is placed to one side to be washed and rewaxed for another use.) This drying can be done easily with warm dry air in fifteen to twenty-five minutes without fear of harming the pigment image.

CLEANING THE WAX.—A film of wax from the celluloid adheres to the surface of the pigment image when it leaves the celluloid. This must be cleaned off thoroughly, or the pigment image will not adhere to the next color. To do this you first mop the face of the pigment with a cheesecloth swab soaked in pure rectified spirits of turpentine. Let this set a few seconds to soften the wax. Then soak a fresh cloth in either benzol (which is also called benzene), or naphtha, and go over the print again. This will remove the turpentine and probably most of the wax. Polish with a dry cloth. Then once more with a fresh soaked cloth mop the entire print with benzol or naphtha. A final thorough polish with several dry absorbent cotton or soft cloth swabs, and you are ready to add the red, which has dried in the meantime. Place the paper with the blue image in cold water to expand for about two minutes, or until fully expanded.

ADDING THE RED.—Pay close attention to the details at this point. Slide the celluloid with the red image face up into a tray of cold water for about one-half minute. Pick up the fully expanded blue image on the paper and lower it face down from end to end (being careful to avoid any air-bells) into the tray above the red image. Place it so that it covers the red image. Pay no attention to registering the images as yet. Hold celluloid and paper together at end and draw slowly out at one end of tray. When entirely out, holding celluloid and paper lightly at each end, lift, and, looking through the celluloid side, bring the images in approximate register. Holding it in rough register, set flat, paper side up, on squeegee board and with a flat rubber squeegee take a light stroke from one end to the other, which will remove the surplus moisture. Register as yet need not be exact. Now place inside a folded blotter and go over lightly with the hand or roller squeegee. Remove from blotter and carefully wipe off the water spots from the back of celluloid.

Now reverse the celluloid paper side underneath with the celluloid side facing you, and with the fingers of both hands slide the blue image one way or the other to coincide with the red. Take the center first, then the corners. If done in a cool room, you need not hurry. Hold the fingers lightly against the margin of paper. Dip fingers in cold water if you are long delayed. When you have it in perfect register (see registration note below), wipe the celluloid side with a dry cloth, and examine carefully for air-bells. If there are any air-bells, you must wipe back carefully with towel to eliminate them. Now wipe the back with folded towel along the long side and across and without any further squeegeeing or rolling lay face (paper side) up and allow to set as before; then remove to warmer room, where it will dry and come off the celluloid. The combined blue and red images will now be on the paper.

Registration Note: If for any reason the paper image does not correspond in size to the image on celluloid when you attempt to register, you can aid this by curving the celluloid in or out, top and bottom or at sides, until correct register is obtained. Copper wire strips are passed through the holes in the celluloid and fastened to hold the celluloid in the proper position. Images registered in this way must be watched while drying, as it may be necessary to let out the wires as they dry.

If the pigment images begin to set before registration is complete, you can put the two back into cold water, separate them, and start over again to register, leaving more water between the two images than before.

ALTERNATE REGIsTRATION METHOD.—Some workers prefer, particularly in smaller sizes, after the images have been lightly squeegeed and rolled between blotters, to effect registration by laying with the paper face down on a clean white blotter and by sliding the top image containing the red image into position over the paper one instead of sliding the paper back as described previously. This method works best with thinner celluloids. With heavy celluloids it is not possible to effect local registration when using this method. The advantage in this method is that it is easier for one to push the red edges in the directions they need to go than to pull the blue in the opposite direction. In any case it is a matter of whatever system one gets used to.

ADDING THE YELLOW.—Proceed with the cleaning with turpentine and naphtha as before, and, in the same manner as already described, superimpose the combined blue and red above the yellow and place thiS to dry, after which it must be cleaned with the turpentine and naphtha as before.

TRANSFER TO FINAL SUPPORT.—YOU now have the three-color print upside down on the temporary soluble support, so called because it is used only temporarily to gather the images together and because, as you will now see, we can dissolve it away from the combined images when we are ready to do so.

A piece of final (single transfer) paper larger than the temporary soluble support of a kind selected, usually the smooth white No. 116 Autotype, is soaked for fifteen or twenty minutes first in warm water and then chilled in cold water.

The image on the temporary soluble support can be trimmed up to the edge of color subject or left as is. The combined image is now placed in cold water to soak for about five minutes or until limp, after which it is placed face down on the gelatin side of the No. 116 transfer in the cold water.

Lift the two from the water together, avoiding air-bells, and squeegee the combined images and support with a flat rubber squeegee into contact with the final transfer. Place between blotters, roll moderately firmly with the print roller and place between blotters under a plate glass for twenty minutes, then hang in the air another ten minutes or until it begins to show relief around print. Next slide the entire combination, temporary soluble side down, into a tray of warm water I05° F. (40° C.) or hotter if necessary. After a few minutes the paper backing of the temporary soluble support should begin to fall away from the combined colored images, leaving them together on the final transfer. As soon as it begins to come off, you can assist by pulling it away gently. If it does not begin to come away, reverse right side up in the water and test the edge with a knife point. If loose, pull away.

If it is not loose, raise the temperature of the water. A little practice will tell you just how hot you need the water for the amount of drying you have given.

Throw away the paper back of the temporary soluble support. The completed color print is now right side up. Bathe gently with the warm water to dissolve any surplus gelatin on the face of the print. Chill in cold water and hang up with clips to dry.

In humid weather at this point the finished print may have a tendency to pucker or reticulate. This can be prevented by bathing for a minute or two in a bath of Columbian spirits and water (half-and-half) immediately on removing from the cold water and drying without further washing. This also shortens the drying time.

MOUNTING.—After the prints are dry, they can be mounted with a dry mounting press or rubber cement and placed under a suitable mat. In some climates it may be necessary to treat the finished print with a 3 per cent solution of powdered potassium alum before mounting.

Finished Carbro prints are sometimes placed for display under a sheet of clear glass, the edges being bound by cellulose tape of a color which harmonizes with the Carbro print.

SINGLE BATH CARBRO.—While many workers avoid the careful study of the effect of each chemical in a one-bath method, others who have made this observation are very successful in its use, eliminating the exacting conditions required with the use of the No. 2 bath.

A successful one-bath worker has very kindly out-lined his procedure for me. Negatives and bromides are, of course, made in the usual way, except that one must learn to be very exact in the bromide quality, as he will get in the Carbro exactly what is seen in the bromide without the variations usually accomplished in the two-bath method. We quote: "First I will describe my idea of a Carbro room. It should be divided into two parts, one for the transfers and one for hot water development. Hot water in the cold room heats it up, which requires more electricity to cool it down again. I have arranged, over a long table or sink, first my tray of chemicals; then my glass for squeegeeing the pigment and bromide together ; next a tray of water for uncurling the tissue, and finally a tray to soak the bromides in.

"Behind me I have a table with several stacks of blotters and a space for wiping off the prints. Over-head is a set of hookS to hang the celluloids on. At one end of the room is a sliding door that opens into the hot water room.

"(It is important to have a filter on your water line.) The new worker should pick out a one-bath formula and study the action of each chemical. This is important, as 90 per cent of the faults are chemical actions and not of the pigment paper.

"You first soak the pigment paper in water to make it limp and then hang it up to drain. (I make six transfers at one time with an assistant, or three by myself, taking forty-five minutes from the start to the hanging for drying.)

"Put the bromides in a tray of water to soak in rotation. Now you soak your first color, in chemical bath, starting the clock on sixty. In one minute I put in the second color, at two minutes I put in the third color. My assistant puts the first bromide on the glass and swabs it with wet cotton. We have a slow flow of water running from a hose continuously. He makes a pool of water over the bromide from this. Now three minutes have passed. I take the first color out of the chemical and squeegee on to the bromide and my assistant puts the fourth color into the chemical. If my tissue is too large over the bromide I quickly trim it with a Gem razor blade and lift the sandwich off the glass and carefully wipe off the back with a clean towel to take off extra moisture, and then place it under a pile of blotters.

"In the meantime my assistant has washed off the glass and placed a new bromide. At four minutes I put the next color on the bromide and he puts the fifth color in the chemical. We continue until all six are on the bromides, which brings the time up to eight minutes. On the ninth minute we have a tray of cold water. ready, into which slide the celluloid wax side up. We now strip the blue tissue from the first bromide. Slide it into the tray of cold water above the celluloid. Draw it out at an angle to avoid air bubbles, lay it on the squeegee board and squeegee firmly with a stiff flat rubber squeegee. In the meantime my assist-ant has prepared the next celluloid and the pigment image in the same way, which is ready to be squeegeed. This is done with each pigment until all are mounted on celluloids. At twenty minutes by the clock we are ready for the hot water. The hot water must also be filtered, as the small tears and scratches that occur in the transfers are caused by small particles of dirt. I then hang my celluloids in a drying machine.

"The one-bath formula is balanced to take the exact image off the bromide—not a softer or contrastier one, but the exact image.

"Thus you must have perfectly balanced bromides (for these I use a condensing-lens type of enlarger which gives more detail and brilliance). Your formula must be changed according to the seasons and the way the city doctors up the water. If you know your chemicals this will be easy.

"In cleaning the wax from a print, I use turpentine, which is a solvent for wax. After the wax is softened, I rub this off quickly with benzol, which has an affinity for turpentine.

"Another thing I find very essential is to wash the celluloids when new, and after each transfer, with Gold Dust soap powder. You will find that after thiS treatment you will have less trouble with the blue.

"My objection to two baths is that you have less control over your even soaking, and get an uneven transfer. It is also hard to duplicate prints exactly with the two-bath method.

"I find that a card index with a record of the temperature of the bromide developer, lens stop and exposure, temperature and humidity of cold room, helps to duplicate for reorders.

"I find a good way to get all of the surplus color off is either to stir up suds or to run water into a tray from a height and then bend the celluloid face down and push it through the suds. The suds take off all of the surplus color. I then rinse it in a change of clean warm water and transfer to cold water for a few minutes before hanging up to dry."

SINGLE-BATH CARBRO FORMULAS

NEWENS

No. 1 Stock Solution

Potassium ferricyanide 1 oz. 28 g
Potassium bromide 1 oz. 28 g
Potassium bichromate (highest purity) 1 oz. 28 g
Water 20 oz. 590 ccm

No. 2 Stock Solution

Glacial acetic acid 1 dr. 3.5 ccm
Hydrochloric acid C. P. 1 dr. 3.5 ccm
Formaldehyde (40%) 10 dr. 35 ccm
Water 12 dr. 42 ccm

For use take:

No. 1—Stock 1 oz. 28 ccm
No. 2—Stock 1 dr. 3.5 ccm
Water 7 oz. 200 ccm

The tissue is soaked for an average of three minutes at 65° F. (18' C.). Shorter immersion gives more contrast, longer immersion less. Less No. 2 stock solution increases contrast, but has a tendency to bald highlights. Increased No. 2 contents give softer results. Use always a matte bromide with no gelatin supercoat.

The combined single Carbro bath should be used for only one run of pigments, three or six, making a fresh lot for the next batch.

ALTERNATE ONE-BATH FORMULAS

AUTOTYPE

Stock Solution A

Potassium bromide 1 oz. 28 g
Potassium ferricyanide 1 oz. 28 g
Potassium bichromate 1 oz. 28 g
Distilled water to 20 oz. 590 ccm

Stock Solution B

Chromic acid 150 gr. 9.7g
Chrome alum 300 gr. 19.4g
Distilled water to 20 OZ. 590 ccm

Soak tissue two minutes in water at 60°—65° F. (16°—18° C.). Squeegee off surplus moisture face down on glass and then immerse for forty-five seconds in the combined bath before squeegeeing on bromide print. Leave tissue and bromide in contact for ten minutes, strip, and mount on celluloid. Leave on celluloid for ten to fifteen minutes before developing. Use for only one set of prints, three or six. Make fresh for next batch.

Use at 60° F. (16° C.) and immerse pigment for three minutes. Squeegee on to soaked bromide print and leave in contact five to ten minutes. Strip pigment from the bromide and squeegee on to the waxed celluloid. Do not use spirit bath at this point, but slide pigment over face of cold water to moisten it before placing on celluloid. Pigment is ready for development after five to ten minutes on celluloid.

The following one-bath formula works very satisfactorily in localities where the water condition is such that the alkaline content of ammonium bichromate holds delicate highlights better than does the potassium bichromate used in other formulas.

Soak pigment three minutes at 60° F. (16° C.) to 65° F. (18 ° C.) and squeegee directly on to bromide as usual.

TRICHROME CARBRO: NOTES AND VARIATIONS.—First let me repeat that it is only by constant practice that you can hope to make successful color prints. Read the instructions and notes carefully, make a trial or two, then read the instructions again and they will be clearer to you in view of your practice. Save trial tests and study carefully before starting a new lot.

Air-bells or irregular spots are due to the pigment not being covered evenly in the No 1 bath. Air-bells may also come from lack of even contact when pigment is squeegeed to celluloid. See notation on page 49 about air in water. Dark air-bell spots come from uneven handling in the No. z bath.

Bromides: If your negatives are too contrasty for Carbro bromides you can soften the prints by using over the lens of the enlarging camera the Eastman violet filter No. 39, which absorbs the colored light and flattens the gradation.

A contrasty negative set and contrasty bromides will in turn give contrasty pigment positives, which wash away in the highlights. Make your negatives softer, your bromides with more detail in the shadows and a slight tint in the highlights. If the particular set you are working on cannot be made over, vary the amount of the control chemicals, either chromic acid or the glacial and hydrochloric acids and formaldehyde, according to the formula you are using. Leave longer in the No. 2 bath to soften the final print.

Develop the bromides until the high-light modeling detail comes through, even though the shadows appear entirely too dense. This shadow denseness can be modified by leaving the pigment and bromide in contact for a shorter time than usual.

In making bromides for Trichrome Carbro by the method described above, the negatives are placed in the enlarger, emulsion side down, as is customary for enlargements. While a reversal takes place in assembling the three images on the soluble support, this is straightened out by the second reversal when transferring to the final support. When using negatives from one-shot cameras in which two images are re-versed, the same negative emulsion plane for enlarging is arrived at by placing the two reversed negatives, emulsion side up, in the enlarger and by raising the unreversed negative by a thickness of clean glass to match. A plate of the same type you are using with the emulsion cleaned off will do.

Celluloids: Clean these frequently with Gold Dust powder or a similar preparation to remove old wax, particularly in the summer months. This is considered by some workers as a preventive for loss of fine detail in the highlights. Do not wax celluloids in a cold room. Nitrate base must be used. Acetate base is too pliable and does not hold the pigment image as well.

Rapid cleaning of used celluloids can be effected by first going over them with

a. gasoline, if the white waxing compound without resin has been used, or

b. with turpentine, in case you have used the wax and resin compound.

Chemicals: No chemicals, other than the sensitizing baths, should be stored in the Carbro workroom.

Cleanliness: The tanks, trays and graduates should at all times be kept perfectly clean. You will find that cleanliness is one of the most important things in Trichrome Carbro.

Color correction: With the best of separations and care in the making of prints, color corrections may be necessary to satisfy your client with a particular subject. These corrections can be made in two ways. The best, but perhaps most difficult, is to compare the assembled colored images and, if corrections are necessary, make them by retouching on the negatives and again try a set of Carbro transfers. If the negatives are properly corrected and the resultant Carbro satisfactory, you can then furnish the printer with a set of positives from the corrected negatives which will correspond to the finished Carbro if the same ratio of exposure is used as in making the bromide.

The second method of correcting is by hand on the face of the print. This method is more prevalent but not nearly as satisfactory to the printer. If the printer is not supplied with the transparencies he must make his own separations from the finished Carbro print. At times the finished Carbro is used in a layout with a celluloid overlay which contains printed matter. When very dense dark tones appear in the Trichrome Carbro, it is sometimes difficult for the printer to get detail in reseparating the finished color guide, but he can in such cases work better from transparencies which you could Supply from the original negative.

Color balance. Grey scale test of a particular batch of pigment and bromide paper for color balance: From a single grey scale negative of any negative in the set, project on your regular bromide paper a 5 by 7 or 8 by 10 print of the grey scale only. Cut this print into three pieces. From each piece make a transfer, one in blue, one in red and one in yellow, giving each uniform treatment. Develop and combine these three on the transfer paper and you Should have a perfect grey. If any one color in the scale predominates, you must lengthen the time for that or shorten it for the other two until you have a perfect grey balance which will now hold good for the particular batch of bromide and pigment you are using, but may have to be varied in subsequent lots.

Cutting: Cutting Carbro sheets from rolls of pigment can be done easily by pulling out the end to about the distance required and letting the end pulled out roll back toward the full part of the roll. Then run a razor blade, paper hanger's circular wheel cutter, pen-knife, or other sharp point across the width where the two rolled parts meet. If pigment becomes dry and brittle from having been kept in too dry a place, stand it for a day or two where it will pick up moisture. A good plan used by many workers, immediately on opening a new roll of pigment, is to saw the roll into two fifteen-inch widths and to roll the entire length around a larger core, such as a corrugated roller five or six inches in diameter.

Cold room: The cold room, if kept at a temperature of between 60° F. (16° C.) and 65° F. (18° C.) with the humidity between 50 and 60, is ideal for working the new non-frill Carbro.

Darkroom: The darkroom (where bromides are made) should be kept perfectly clean.

Trays should be free from rust spots and chemical stains. Pigment is best kept in another room.

All chemicals should be stored in cabinets, preferably in another room.

Density of pigment images: When the developed pigment images are to be stripped on paper as a color-print, they must not be very heavy or the resultant print will be too contrasty and dark. The be-ginner is apt to make the individual colors too heavy. More time in the No. z bath or lighter and softer bromides will remedy this. The correct colors, blue in particular, are usually a little on the thin side, as we would judge in black and white.

Drying: If you leave the developed pigments on the celluloids too long in a hot dry room, such as the average steam-heated office, they are apt to dry up and roll off the celluloids.

The length of time the soluble temporary and final supports should dry in contact depends on the temperature and humidity of the room. They should be left until they are fairly dry and then separated in hot water 100° to 110 F. (38° C. to 430 C.).

Drying: Some workers have constructed drying cabinets to aid in the prompt, clean drying of the Carbro images in their various stages. These usually consist of a cabinet in which the Carbro images are hung on wire stretched across at intervals at the top ; at the bottom a small fan and an electric heating unit, each of which can be turned on separately, are in-stalled. Between these heating and circulating units are stretched a filter of two layers of cheesecloth to prevent dust and spread the circulation of the air and heat.

Drying the complete color-print can be hastened by immersing for a minute or two in an alcohol bath (Columbian spirits) and hanging to dry without further washing. Do not go near an open flame with a print fresh from alcohol.

Filtering water: It is almost a necessity to have a filter system which will provide you with clean water, free from grit, both cold and hot, if possible. This gives you added protection in the making of your solutions and in the handling of the gelatin image. You will also avoid many small abrasions which come from particles of grit in the tap water.

Frilling or wrinkling of the pigment image on the celluloid when developing is due to either one or a combination of the following:

a. Too hot and humid a workroom in the earlier stages. If the temperature cannot be reduced, make the solutions colder by setting them in trays filled with cracked ice, and slide the pigment and bromide and later the celluloid and pigment during their bleaching and drying period into the shelf of an electrical refrigerator, leaving the door ajar.

If there is no way of reducing the temperature and humidity, shorten the time in the No. 1 bath to two, or one and a half, minutes. An alcohol bath is also used to prevent frilling.

b. When the pigment is separated from the bromide, place the pigment face up in the tray of alcohol and water for one to two minutes (half alcohol [Columbian spirits] and half water prepared in advance and allowed to cool, as it is warm when first mixed). The alcohol absorbs much of the moisture from the gelatin, keeping it firm, which minimizes frilling later when developing in the hot water. Mount on celluloid with-out draining.

When alcohol is used, it is not necessary to pass pigment through water before placing on celluloid. Many workers make use of the alcohol bath instead of using albumen on the celluloid.

Do not expose to too strong a light when in alcohol or rock the solution much, as this may cause a slight fog over the entire print. During development, if you notice a tendency to frill, remove at once and place in the alcohol bath for about a minute and then return it to the developing water, slightly warmer than before.

c. Too short a contact with the bromide will give a thin image, which is apt to frill.

d. An alcohol bath which has been used several times may account for frilling, by being no longer able to absorb water from the pigment.

e. One ounce (30 ccm) of a 7 per cent solution of chrome alum to each 64 ounces (i800 ccm) of hot developing water will also help to prevent frilling. Too much chrome alum may cause veiling or fogging by preventing full clearance of pigment from the gelatin.

Highlight loss or mottle: The loss of delicate high-lights, which are most noticeable in the blue, is a difficulty which is often encountered by the beginner and occasionally by the experienced worker.

While many theories have been advanced to account for this difficulty, the writer feels that this trouble can be traced and divided into two types—chemical and mechanical.

Chemical. Bromide prints must be thoroughly washed to remove all traces of hypo. Hypo remaining in the print will react with the ferricyanide of potassium of the bleaching solution. If prints are neutralized for one minute (immediately on removal from the fixing bath) in a 1 per cent solution of carbonate of soda, and then washed as usual, they will be aided in two ways: first, the neutralizing of the acid con-tent will allow the hypo to wash out more thoroughly and in less time; second, the slight softening action of the alkali (carbonate solution) will leave the emulsion in a softer and more even condition when contacted with the pigment. In some localities chloride of lime is used to purify city water. This blocks up the silver in the delicate highlights and prevents even bleaching. This can be remedied by bathing the print after washing in a 3 per cent solution of acetic acid for a minute or two and then rewashing for a short while.

Mechanical. Probably more frequently than by chemical cause mottle is occasioned by uneven squeegeeing and lack of pressure in squeegeeing. The nearest perfect remedy for this is a mechanical wringer squeegee by hand or motor which brings the pigment and bromide quickly and evenly into contact with a pressure which brings out every fine detail in the bromide.

If you squeegee by hand, learn to place the pigment quickly and evenly over the bromide and squeegee with a heavy pressure, using a short stub rubber type (not the long soft velvet kind squeegee), to press the pigment into contact. Naturally, in warmer weather one does not need to use as much pressure as in colder weather. Unless you see a distinct relief in each pigment when stripped from the bromide, the chances are you will not have all the pigment highlight detail. If the pigment adheres too tightly to the bromide, after bleaching, slide the two into a tray of cold water and separate in this way. In hot humid weather, a tray of half alcohol (Columbian spirits) and half water can be used to remove the moisture and Strengthen the pigment for development on the celluloids.

Insolubility: If the pigment will not develop or develops very reluctantly, you may have:

a. Left it too long a time on the celluloid, causing it to dry and become insoluble.

b. Kept the pigment in a room with chemicals, such as ammonia, formaldehyde, etc., the fumes of which have affected its solubility. (Keep the pigment in a different place from the bromide paper and darkroom chemicals.)

If you have had the tissue a long time or it has been improperly stored before using, cut a small strip and dip into a cup of water about 110° and note if the pigment becomes soft and dissolves on shaking. If so, it is in good condition for use.

c. Used denatured alcohol or impure wood alcohol, which has made the pigment insoluble.

d. Used too much chrome alum in the sensitizing bath.

Light: While the entire operation of sensitizing, bleaching, and developing can be carried out in the ordinary Mazda-lighted room, it should not be worked near sunlight or other very bright light, such as arcs, etc. If worked in too strong a light you are apt to get a reversed image, negative instead of positive, when developed in the hot water.

Patches: Circular light or dark patches that appear in development are due to humidity and heat during the operation. Shorter time, one and a half minutes in No. I bath, and less drying on celluloids, will remedy. Start the development at 1130 to 118° F. (450 C. to 48° C.) and strip the back off immediately you reverse the celluloid in the warm water. With the back of the paper off, the hot water penetrates evenly and at once to the entire image and overcomes these patches.

Pigment: If the pigment backing refuseS to strip in development or the image refuses to develop after the backing is off, you have in some way caused the pigment to become insoluble. Too long a drying period on the celluloid or drying or handling in too strong a light after taking from the No. z bath will have this effect. If the pigment has been stored near chemicals such as formaldehyde and acids, this may cause in-solubility which will not be noticed until you reach the developing point. If the tissue has been kept for a long time, test a piece before using, as described under the heading "Insolubility."

If the bromide print sticks to the pigment and refuses to separate after bleaching, your working conditions are too warm, causing the gelatin to melt.

Pigment surplus: Just before separating the pigment from the bromide after bleaching, trim off with long shears or razor blade the surplus pigment up to about one-quarter inch of the bromide. This eliminates the dissolving away in the developing water of the pigment color which is no longer necessary.

Reversal: Occasionally a reversed image, due probably to too much light while sensitizing or drying the pigment, will appear when the developing begins. This as a rule will change back to a positive as you continue the development.

Registering: If you have trouble with scratching the colored images during the time you are learning to register, it is probably due to grit in the water. Dip-ping them in a thin gelatin solution before assembling will avoid this. With experience, however, you will not find this necessary. Filtered water should be used at this point.

GELATIN FORMULA.—An ounce (29 grams) of Nelson's No. 1 is put into a jar or jug with three pints (1420 ccm) of water and allowed to stand and swell for about half an hour. The jug or jar containing the thin jelly is placed in a saucepan of warm water over the fire or a gas ring until the gelatin is fully dissolved. A temperature of about 1300 F. (54° C.) will be sufficient for this. Add two or three drops of carbolic acid as a preservative. For use, warm the solution, filter through fine muslin, and pour into a dish, keeping the temperature at about 70° F. (20 C.).

Reducing the pigment image: While it is normally better to make a new set, the following suggestion may help.

Red: The red image can be reduced by bathing it in a weak bath of potassium permanganate and sulphuric acid:

Potassium permanganate 10 gr. 0.7 g
Sulphuric acid 20 drops 1.2 ccm
Water 20 OZ. 550 ccm

Be sure to add acid to water slowly. It is dangerous to add water to acid.

Followed by bath of

Potassium metabisulphite 50 gr. 3.5 g
Water 20 OZ. 550 ccm

Make the potassium permanganate fresh for each print. Give a final wash of five minutes after reducing.

There are no specific methods of reducing the blue and the yellow. A weak solution of M.Q. developer followed by a formaldehyde bath brings the blue down at the time, but it usually comes back after a day or two.

Plain hypo is sometimes used on the yellow. Sodium hydroxide in very weak solution is sometimes used. The blue can be reduced best in the light highlights with a soft kneaded rubber eraSer.

In Marton's "Treatise on Carbon" he mentions for reducing carbon prints the use of:

Ammonium sulphocyanide 1 oz. 29 g
Water 100 oz. 3000 ccm

to which is added one drop of ammonia.

Another formula offered by Marton is:

Water 32 OZ. 900 ccm
Sulphuric acid 2 drams 7 ccm
Ammonium persulphate 125 gr. 8 g

Soak pigment for thirty minutes, then develop again in hot water. When sufficiently reduced, bathe in a solution of sodium sulphate and rinse in cold water.

Some local abrasive reduction can be done with a cotton swab moistened with alcohol.

Sensitizer: Some color workers prefer the sensitizing and control solutions normally recommended for monotone Carbro. For those who wish to try out these formulas, known as Carbro No. 1 and No. 2, ready-made solutions can be purchased or may be made up as follows:

Carbro Concentrated Solution No. 1

Potassium bichromate 1 oz. 28 g
Potassium ferricyanide 1 oz. 28 g
Potassium bromide 1 oz. 28 g
Water 20 OZ. 590 ccm

Carbro Concentrated Solution No. 2

Glacial acetic acid 1 oz. 3.5 ccm
Hydrochloric acid (pure) 1 oz. 3.5 ccm
Formaldehyde 40 per cent 22 OZ. 77 ccm

In making up the concentrated solution No. 2, the addition of 1 1/4 ounces (50 ccm) of water will prevent any precipitation in cold weather.

Working Bath No. 1

No. 1 Concentrated solution 6 oz. 175 ccm
Water 18 oz. 525 ccm

Working Bath No. 2

No. 2 Concentrated solution 1 oz. 3.5 ccm
Water 32 to 48 oz. (112 ccm to 168 ccm)

The No. 2 bath should be renewed frequently, as it is altered by the No. 1 solution transferred to it on each immersion. The baths should be used at a temperature of 60° to 65° F. (i6° to 18° C.).

Sensitizing: An alternate method of handling the pigment in a two-bath sensitizer is to lay the pigment, when removed from the No. I bath, face down on a sheet of absolutely clean glass and squeegee out the surplus moisture, leaving it there for a moment while the bromide print is arranged on the glass or squeegee board. Then pick it up from the glass and immerse as usual in the No. 2 bath.

A convenient method of immersing the pigment in the No. 2 bath evenly and quickly is to lay pigment face up on a sheet of glass next to the No. 2 tray and, taking hold of both sides at once with both hands, pull over edge of tray and through solution with one motion.

Surfacing prints: If, on drying, parts of the print have more lustre than others because of heavier pigment deposit, this can be regulated by soaking again in cold water and redrying.

A better plan, however, is to wax the entire surface of the finished print with one of the standard print lustres, such as Probus print lustre.

Stripping: Difficulty when stripping pigment from bromide or pigment backing from celluloid in development indicates that you have let them dry too long before stripping. Weather conditions must be considered and the time varied accordingly, giving less time in hot weather, as little as five minutes if necessary. Light sponging of the blotters will delay the drying out of the pigment.

Squeegeeing: When large-sized prints, say 14 by 17 to 16 by 20, are being made regularly, a squeegee roller machine is sometimes arranged to bring the pigment and bromide together quickly and evenly. See your dealer, or illustration in "Photographic Printing Processes" by Wheeler, page 129.

For those who do not wish to go to the expense of a specially built wringer for this purpose, a very practical one can be made with the aid of an ordinary "Easy" type wringer. A narrow slot is cut in a table and the wringer turned on its side with the opening in the table directly below the center of the rollers. Affix solidly with L brackets at each side. A V-shaped arrangement of masonite board is placed above the rollers at a 450 angle. Two sheets of celluloid about 10/1000 of an inch thick of a width two inches narrower than the roller width and long enough to handle size of print you wish to make are hinged together at one end with adhesive tape. When opened up in a V shape this celluloid press lies flat on opposite sides of the 45° masonite rests. Guide marks for placing bromide and pigment can be made on pack of celluloid with a blue grease pencil.

The bottom part with the tape is inserted into the rollers and the handle given a slight turn to catch it firmly. By placing the bromide on one side face out, and the sensitized pigment face out on the other, a quick turn of the handle will bring them firmly together and pass the celluloid sandwich with pigment and bromide together down through the opening in the table. A masonite board fitted at a slant below the opening in the table with a stop at the proper distance will catch the celluloid. The celluloids are then opened carefully and the pigment and bromide removed. (Wipe the celluloid carefully with a sponge before using it again.) The squeegeed sandwich is placed between wax paper as usual.

An alternate method of squeegeeing the pigment is to place the bromide prints face up, each on a separate piece of glass, and go over them lightly with a flat squeegee. Wipe off the face with a damp cotton wad and set in a row. Do this when you are ready to start sensitizing. As you begin to sensitize, set the glass with the corresponding bromide on the left edge of a large tray of water. When the pigment is lifted from the No. 2 or control bath, hold it by the right hand, slide the glass with bromide into tray of water with the left, and drop pigment on face of bromide in the water. Hold both pigment and bromide firmly with fingers of left hand, withdrawing quickly toward left on to a flat surface, starting to squeegee with right hand as soon as bromide and pigment are level. This method insures good, even bleaching action, avoiding mottled or washed-out highlightS.

In addition to the wringer-type roller machine for squeegeeing, workers make use of many handy methods and devices.

One simple method of placing pigment in the approximately correct position to cover the bromide when squeegeeing is to have a guide of adhesive tape on the glass at the left, of the same width as the pigment. When the end of the pigment is laid parallel and upon the adhesive tape, it gives a place to grip the tissue for squeegeeing, knowing that the opposite end and sides will come in the right places.

Another improved idea for professional use is to mount on the work table at the right an old-fashioned paper clip board (these are now supplied with composition rubber boards). Place the glass with the bromide print squeegeed into place, so that the right end of the glass is just caught under the hinged clip. Pour a pool of water on print. As soon as the pigment is lowered upon the bromide from left to right, push the glass and left end of pigment into the hinged clip, which will hold the pigment firmly, leaving both hands free for squeegeeing.

Still another simple method in use is to mount at left end of squeegee board a hinged clamp with handle at top and rubber strip underneath. This can be thrown back until pigment is laid on bromide and then brought over quickly, the rubber gripping the pigment across the end while you squeegee. This hinged arrangement can be made up complete on a flat board covered with 1/16-inch aluminum and waterproofed.

Another worker has a flat rubber squeegee board with the adhesive tape guide, and at the left end fastened on the under side is a piece of rubberized cloth about the size of the board. This cloth is kept folded back at left. As soon as the pigment is down on the bromide, give it a light stroke with the flat squeegee to put it in place, then pull the rubberized cloth over entire surface and complete the squeegeeing over the top of the cloth.

Standardizing: Success in Trichrome Carbro depends on how carefully you standardize your working conditions. Check carefully and record all your work-room conditions so that you can duplicate them, or know what to do to vary the result. Determine the exact depth of the grey scale in the bromide, time of development, temperature, immersion in the bath and other handling which gives you the best results.

Storage of the pigment: UnleSs the pigment is kept in a cool place, it will become dry and brittle and hence hard to unroll. Metal tubular storage cans are useful for proper storage. Workers usually saw the 30-inch wide roll into two 15-inch rolls with a fine saw. When the rolls are first opened, they can be re-wound over a larger tube about four or five inches in diameter, which will make it easier to handle. If the pigment becomes brittle, place it in a damp place.

Transparent support: While the general run of Carbro work is done by means of temporary soluble sup-port, Color Photographs of London hold British and American Patents (British, 1930, No. 340,605 and No. 357,548; American, No. 1,891,571—December 20, 1932, No. 1,915,873—June 27, 1933), which cover the use of permeable cellophane as either permanent or temporary support.

Transfer: If the colored image refuses to transfer from the celluloid to the temporary soluble support, waxing may have been unevenly done, or you may have used the unwaxed side of the celluloid on which to develop the image, or you may have used a cheap grade of alcohol containing some denaturant which prevents transfer. Use only Columbian spirits, a good grade of wood alcohol. Do not use denatured alcohol. Be sure also that you are putting the face or gelatin side of the temporary soluble support next to the gelatin of the pigment.

If the complete print assembled on the temporary soluble support refuses to transfer to the single transfer, you may have in some way hardened the assembled image to prevent transfer, used incorrect alcohol, or you may be trying to transfer to the back of the single transfer. Always mark transfer papers on the back before wetting.

Transfer papers: Any good grade of paper containing a hardened coat of gelatin may be used for the final transfer. Defender backing paper is used by some workers. Photographic papers such as Azo, Velour Black, P.M.C., Agfa Brovira, etc., can be made use of by first fixing them out without exposure in a regular acid fixing bath containing alum, which will sufficiently harden the gelatin so that it will hold up in the hot water.

Transparencies by Carbro: Very beautiful transparencies can be made by the Carbro process either by developing the Carbro image upon thin gelatin-coated celluloids which are bound together, or by transferring the three images, after they have been collected in register upon the temporary soluble sup-port, to a film or glass support. An old plate or film that has been fixed and hardened without being ex-posed will serve as a base. The latter method makes a fine transparency without subsequent losS of registration by separate images shifting after being bound together. Carbro bromides for transparencies should be slightly darker than those for prints, or the time in solutions adjusted to give a stronger image when viewed by transmitted light.

Another simple method of making transparencies by the Carbro process is to fix out without exposure three pieces of thin base film such as Wash-Off Relief and develop the three Carbro images without waxing on the film side. When dry, these can be bound together in the usual way for transparencies.

Still another simple method is to make thin base film positives (instead of bromide prints). Sensitize the pigment, squeegee into contact with the transparency, and place between blotters for fifteen or twenty minutes. Then develop in the usual way in warm water, chill, and dry. After drying, the weak silver image left in the emulsion of the film can be bleached out of the red and blue with Farmer's reducer (hypo and ferricyanide) and from the yellow with potassium permanganate and sulphuric acid. Wash well, dry, and bind together between glasses. Positives for this purpose must be entirely free from fog or they will pick up color in the whites.

Variance in Carbro B solution: If you have difficulty in getting all the delicate detail in your Carbro image, make up test solutions of the B stock solution, varying the chromic acid and chrome alum and keeping a careful record, using bromides of the same subject in all tests. In this way you will soon find your correct balance for the water and other conditions under which you are working.

This same procedure also applies to the chemical make-up of the alternate bath which makes use of the No. 2 stock solution with formaldehyde, glacial acetic acid, and hydrochloric acid.

Waxing compound: Some workers prefer to mix their own, using the regular (dark brown cake) Auto-type waxing compound, which they shave into small pieces and dissolve in pure rectified spirits of turpentine. Celluloids so waxed must be done in advance to allow them to set before use or before dipping in albumen bath.

Another method is to make use of the Autotype Trichrome waxing compound (white) which comes in round cakes in a metal container.

A pad of flannel or other Tintless cloth is wet with benzol and rubbed over the cake of Trichrome wax with a circular motion, picking up a layer of wax, which is then applied to the celluloid, rubbing it in all over in the same manner you would clean a ferrotype plate. Then take a fresh piece of flannel and polish as hard as you can, rubbing off what appears to be all of the wax applied. This will leave a thin, hard layer of wax on which to develop the Carbro image. Clip the upper right corner of the celluloid so you will know that it is face or wax side up when the nick is in that corner. The celluloids are now ready for use or for coating with the albumen, as is your usual custom. Celluloids should not be waxed cold, only at normal room temperature.

In an emergency you may wish to make your own waxing compound. We give below several suitable formulas.

WAXING FORMULA

Beeswax 24 gr. 1.5 g
Resin 24 gr. 1.5 g
Pure rectified spirits of turpentine 36 oz. 966 ccm

Make well ahead of time. Scrape beeswax and resin in small pieces. Set bottle in a container of hot water. Do not heat over open flame.

WAXING FORMULA, MARTON

Pure wax 40 gr. 2.5 g
Resin 24 gr. 1.5 g
Benzol (benzene) 10 oz. 300 ccm

Dissolve the wax in the benzol, adding a small portion at a time. Shake well and add the resin.

Apply to celluloid with a piece of flannel. Allow to set ten minutes, then polish well with a dry flannel cloth. Celluloids are best when used the following day.

WAXING FORMULA, MARTON

Pure beeswax 75 gr. 5 g
Resin 35 gr. 2.2 g
Benzol 10 OZ. 300 ccm
Turpentine (spirits) 8 oz. 237 ccm

Dissolve the wax in the benzol and the resin in turpentine, mix the two, and let it stand until clear. Coat and polish celluloids twelve hours before use.

Workroom: While you can conduct your first experiments in any cool place or do occasional jobs in ordinary temperature and humidity conditions, for standard production a workroom should be set aside. In a great many climates, a temperature controlled workroom has been found necessary, if a standard daily production is essential. Do not expect to make Carbro or any other color process in a darkroom which is barnacled in every nook and corner with hypo crystals and other chemicals. Set aside a clean room about 10 by 12 feet. Call in your local air cooling and conditioning concern, who will tell you just what must be done to put this space in condition to enable you to have regularly when working a temperature of 65 ° F. (18° C.) and a humidity as dry as 50 to 60. These units are not very expensive and can usually be purchased on time payments from the same firms who supply electric refrigerators. With such a workroom as I have described, equipped with clean trays, graduates, etc., you will have eliminated practically all the risks encountered by Carbro workers. This room should be used solely for the making of the Trichrome Carbro transfers. Negative development, bromide prints, etc., are done outside.



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