Color Photography - Reliefs And Imbibition For Color Prints And Transparencies
( Originally Published 1938 )
AUTOTYPE-DYEBRO AND EAsTMAN WASH-OFF RELIEF
THE use of gelatin relief positives, dyed for transparencies or as carriers to transfer dye in proper proportion to paper for color prints, comes under the heading of imbibition, as they absorb or imbibe the color into which the positive is placed. Leaving the colors in the positives and binding them in register gives a color transparency. If, however, the freshly dyed still wet positives are placed in contact with damp gelatin-coated paper, the color migrates or transfers from the gelatin of the film into the gelatin of the paper. Successive transfers of the three complementary colors give a complete paper print in color.
For all practical purposes under this heading, it is only necessary for us to deal with the Autotype Dyebro and Eastman Wash-Off Relief methods. While similar methods such as Pinatype and Jos-Pe are avail-able, they are not as simple or practical as those mentioned above. Readers interested will find the Pinatype and Jos-Pe processes described in Wall's "Practical Color Photography."
AUTOTYPE DYEBRO RELIEFS.—From a set of three-color separation negatives, bromide prints are made in the same manner and with the same care as we have described under the making of the bromides in Trichrome Carbo on page 35, except that the bromides should be reversed.
From these bromides we proceed to make and develop on celluloid supports (not waxed) three Carbro images, using Autotype Dyebro carbon, a pigment paper which gives only a faint grey outline as a guide in the warm water development. Follow the exact procedure given for Trichrome Carbro, except that the celluloids are not waxed. Make use of the one-bath Carbro formula and procedure given on page 60, which sensitizes and controls at the same time. The Dyebro images develop easily on the celluloid without frilling, as there is no undercoat of wax. After development, the three print plates, as we now call them, are hardened for five minutes in a 5 per cent solution of formaldehyde and then washed in cold water for ten minuteS and hung up to dry.
These gelatin reliefs when dry are ready for dyeing. Failure of the reliefs to take up the dye is an indication that they have been hardened too long or were not sufficiently washed after the formaldehyde solution.
DYEING THE RELIEFS.—For best results, use the regular Dyebro dyes supplied by the distributors of the Dyebro pigment paper. These dyes are prepared in trial sets of one tube each of blue-green, magenta and yellow, also in ounce bottleS of individual colors.
Dissolve in boiling soft or distilled water, according to the instructions on the tube or bottle, and store in dark bottles or subdued light.
With the dyes ready, prepare a sheet of Autotype No. 120B, a Semi-gloSs gelatin-coated paper, about an inch larger than the image, by soaking it in cold water for ten or fifteen minutes.
Place the Dyebro relief blue printer in a tray of the blue dye. (Be sure each relief is properly marked so that you will soak it in the proper color.) When using Dyebro prepared dyes, soaking takes about thirty minutes. Longer soaking will do no harm.
At the end of the soaking time the blue is ready to transfer to the gelatin paper, which is already soaking in the cold water.
A plate glass is prepared, preferably on a grating over a sink. The gelatin paper (120B) is taken from the water, laid face up on the plate glass and wiped off with a damp cotton swab.
The dyed blue matrix is now rinsed vigorously in one or two changes of a weak glacial acetic acid bath (i dram (4 ccm) glacial acid to 125 oz. (334 liters) water). This clears the surplus color and prevents the dye from bleeding. Now lay the matrix dye side down upon the face of the gelatin paper and squeegee firmly into contact from all directions. Have prepared on a table near by a plate glass, over which is placed a damp, lintless, smooth cloth. Pick up the matrix and paper which have been squeegeed together and place them paper side down on the glass with the damp cloth. Above this place another plate glass to obtain even pressure.
The transfer of the Dyebro dyes to the paper usually takes twenty to thirty minutes, according to the strength of the dyes and temperature of the room. A warm room is preferable. The end of the paper can be lifted at one corner and the strength of the dye transfer examined. If not dark enough, it can be squeegeed down again and left for a longer period.
While the blue dye is transferring, the red and yellow print plates are being soaked in their respective dye baths. As soon as the blue image iS strong enough, it is peeled from the celluloid. The blue printer celluloid is rinsed and dried for future use.
The blue image on the paper, which should be still damp, is placed again on the plate glass over the sink. The red printer is taken from the dye bath and rinsed, as before described, in the acid bath.
In order to facilitate the registering of the red print plate on the blue image, a thin piece of celluloid is dipped into a fresh acid bath and laid above the blue paper image about three-quarters of an inch in from its left side. The red image is placed above the celluloid and moved around until in perfect register. The red printer and blue paper print are then held firmly at left side beyond the edge of the celluloid and the celluloid slipped out. The two are then firmly squeegeed as in the first case. This sandwich is transferred to the damp cloth upon the plate glass and the top glass again replaced to insure contact.
Examination of the combined blue and red colors and the subsequent addition of the yellow is carried out in the same manner.
If the finished print is weak in any particular color, a second application of that color can be made while the print is still damp. If the entire print is too heavy, it can be lightened by squeegeeing in contact with a gelatin-coated plate (a fixed-out unexposed plate will do) for a short time, during which some of the colors will migrate to the gelatin of the plate. This reducing or lightening action can be watched by lifting the corners, as described before.
CLEANING THE PRINT PLATES.—After repeated use the printing plates become stained with the dyes, which makes registration difficult. In this case the plates can be cleaned again by washing in a bath of
Potassium permanganate 31 gr. 2 g
As soon as the plates are again clear of the dye, transfer to a tray containing a 5 per cent solution of sodium bisulphite until the brown coloring is gone, then wash well and the plates are again ready for use.
DYEBRO TRANSPARENCIES.—If one wishes to make transparencies by the Dyebro process, it is only necessary to dye the print films in the respective dyes, rinse in the acid bath, and hang up to dry, after which they can be bound together. The transparency images Should be heavier than those intended for transfer to paper.
If one wishes to check the color balance of the three images before transferring to paper or binding as transparencies, this can be done by first dyeing all the reliefs as outlined, rinsing in the acid bath, and then laying carefully one above the other in a white enameled tray containing a fresh batch of the weak acid solution.
VARIATION OF CONTRAST.—The contrast of one or all of the colors can be increased by adding to the dye baths a few drops at a time of a 5 per cent solution of acetic acid. Reliefs must be removed while adding the dye and the print plate allowed to soak again for ten or fifteen minutes to allow time for the increase of contrast.
Contrast may be softened or print weakened by rinsing the dyed relief for a minute or two (watch carefully as this requires only a slight tint to appear) in water and returning it at once to a weak acid and water bath.
EASTMAN WASH-OFF RELIEFS.—While for some time experimental workers have made use of the Eastman Duplicating film, a slow fine grain emulsion on a thin (approximately .00550 inch) base, for making gelatin relief images by bleaching and hardening of the gelatin, the Eastman Kodak Company since 1934 have been offering a more suitable film for this purpose called Eastman Wash-Off Relief film, together with a set of dyes and a complete method of making and dyeing relief images for three-color photographic prints, known as Eastman Wash-Off Relief Process. Inasmuch as we are advised that occasional changes are still being made in the instructions for use with this material, we will outline its present procedure, with the added suggestion that the reader ask the Eastman Kodak Company of Rochester, New York, for a booklet containing later developments.
MAKING THE POSITIVES BY EASTMAN WASH-OFF RELIEF FILM.-This being a silver emulsion, you can work by contact or projection, using, of course, the usual set of separation negatives with the balanced grey scale. Printing must be through the back of the film, so that the subSequently hardened and washed-off relief will cling to the film base. The printing is done through a Wratten violet filter No. 35, which is placed over the light source to improve the tone rendering of the positive.
If the grey scales in the negatives are balanced, each exposure will be the same. If otherwise, slight differences can be adjusted in the exposure. The exposure must not be long enough to go through to the face of the emulsion, as this will make the entire film insoluble. It should, however, be long enough to only slightly grey or veil the highest light where color detail is desired when viewed from the back before fixing.
The developing is done with the Eastman D-11 formula for five minutes at 65° F. (18° C.) in a tray or tank. If developed by tank, it should be lifted about once every minute, drained and replaced. Do not at-tempt to vary the development time, as it is deter-mined so that the image will develop clear through to the film support.
After development rinse in a standard acetic acid short stop (water 32 oz. (I litre), acetic acid 28 per cent 1% oz. (48 ccm)) and wash for five minutes in running water. You are now ready for the bleaching in formula R-10A.
The film is placed in the bottom of a tray and the bleaching solution (about 8 ozs. to an 8 by 10 film) is poured over its surface in one motion. Rock the tray immediately and constantly until the film is entirely bleached ; otherwise, the film may bleach unevenly, leaving streaks. Two minutes are generally required. The bleaching bath is thrown away after use, and a fresh supply used for the next film. Transfer directly to the warm water bath without washing.
WASHING OFF OR DEVELOPING THE RELIEF.—NOW the film is ready to wash out the gelatin relief, which is usually completed in four trays of water 1250 F. (52° C.) with about one minute in each tray. Prepare the water in a tray and slide the film into the water.
Do not pour the water over the relief or touch the surface of the film. Longer washing than four minutes may affect the delicate highlights.
The reliefs are now fixed with the F-24 bath at this point until clear, and then thoroughly washed for five minutes in running water.
A faint brown image (similar to that obtained when bleaching black and white prints for sepia toning) will now remain. This is preferably removed to facilitate judging the dyed films later, and to obtain more rapid transfers to paper. This is done by immersing in a permanganate bleaching bath, using solutions A and B in formula R-2. The brown image will bleach out in about one minute in this solution, after which the film is washed three minutes and then cleared of the brown manganese dioxide tint by immersing for about one minute in the non-hardening hypo bath formula F-z4. The relief is now washed ten minutes and then bathed for five minutes in a 5 per cent formalin bath. Rinse and dry before dyeing. While the relief can be dyed up at once while wet, it is better to dry it at this point and proceed wtih the dyeing later.
A SUGGEsTION.-A worker in this process has been kind enough to outline hiS method of tray developing. The three exposed films are developed at one time in a clean enamel tray Slightly larger than the film. Keep emulsion side down and rotate from bottom to top for five minutes in the D-11 developer.
Pour off the developer, fill the tray with clean water, and rinse in five or six changes of clean water.
Next bleach, emulsion side down, in a tray of the R-10 bleacher. Rotate in solution as before, to secure even bleaching. Pour off bleacher and rinse in two or three changes of water and place, emulsion side up, in a tray of cold water, then turn on the white light. Washing off the relief, fixing and cleaning continue as outlined in the instructions here given. The method outlined above, including all operations ready to dry, takes about one hour.
FORMULAS DEVELOPER (KODAK FORMULA D-11)
Water (about 125° F.) (52° C.) 16 oz. 500 ccm
Dissolve chemicals in the order given. Formula D-11 i used at 65° F. (18° C.) in either tank or tray will develop EaStman Wash-Off Relief film sufficiently in five minutes.
NON-HARDENING FIXING BATH (KODAK FORMULA F-24)
Water 16 oz. 500 ccm
For use, take one part of stock solution A, two parts of stock solution B, and 64 parts of water.
Important: When preparing stock solution B, always add the acid slowly to the water, while stirring the water rapidly. Never add the water to the acid, or the solution may spatter on the hands or face, causing serious burns.
DYEING THE RELIEF AND TRANSFERS.—The regular set of Eastman A-blue-green, B-magenta, C-yellow are dissolved, according to the directions on the tubes, in 16 oz. (500 ccm) of boiling distilled or soft water. Water which contains iron salts or alkali will not do. After dissolving allow to cool and then add 4 ccm (1 1/4 drams) of formalin solution to each 16 oz. (500 ccm) of dye solution. This acts as a preservative against mold and thus lengthens the life of the dye solution. Filter through a rapid filter paper and store in stoppered bottles.
For small sizes, half of the dyes can be mixed at one time in 8 oz. (250 ccm) of water. Some workers prefer to use a smaller amount of dye and throw it away each time. The three reliefs are soaked thirty minutes each in their proper printing color with frequent rocking of the trays, when they are ready for examination.
As soon as the stained relief is removed from the dye bath, it should be washed to remove the excess color in two changes of a dilute acid bath 1/2 per cent. Acid rinse for the dyes of the Eastman set is made by dissolving 1/4 oz. or 7.5 ccm of glacial acetic acid in 50 oz. or 1 1/2 liters of distilled water.
Shake the film or rock the tray vigorously to eliminate the surplus dye. The use of the acid in the rinse water prevents the bleeding of the dyes. The individual dyed reliefs are left in a fresh tray of the per cent acid until ready to transfer to the paper. (Rinse in 1/10 per cent acetic acid solution before making transfer.)
With the three reliefs cleared in the acid baths, one can at this point check the color balance and general density by laying them carefully one above the other, blue, red and yellow in registration on the bottom of an unchipped white enamel or porcelain tray.
If they appear by the reflected light to be correct, you are ready to proceed with the transfer to paper. With Eastman dyes a scale of greys should have a slightly greenish hue (olive grey) before transfer. In transfer, this becomes grey.
The magenta dye intensifies slightly when transfer is made; so when checking color balance in dyed reliefs this color should appear to be slightly weak.
Corrections that can be made at this point are:
INCREASE OF CONTRAST.—Add a small quantity at a time of a 5 per cent acetic acid solution (1/2 oz. or 15 ccm of glacial to 10 oz. or 300 ccm of water) to the dye solution and again soak the dyed relief. Start off with about fifteen minims (i ccm) and increase slowly until desired effect is obtained. Add approximately the same amount of acid solution for each color. Hold relief out of solution each time while acid is being added and mixed.
To REDUCE CONTRAST.—The dyes can be removed with a dilute Solution of ammonia water, 1 dram (1 ccm) of concentrated ammonia to 3 oz. (100 ccm) of plain water, followed immediately with a bath of plain water, after which they are again redyed in a dye solution containing less acid than previously.
A further dilution of the original dye bath before staining will also tend to give you weaker results in following sets. With a weaker dye solution, the staining up of the films will take longer.
If one or more of the stained reliefs is much too heavy to balance, it may be necessary to make another set of reliefs giving less exposure to the colors which are too strong.
If on examination on the enameled tray bottom, one color or the other is slightly heavy for color balance, this can be remedied by rocking face up in a tray half full of water in the same manner as you develop a single plate, rolling and rocking from end to end and side to side, to insure even washing down of the colors. As soon as the water acquires a light tint of the color being reduced, remove the film to the dilute acid bath originally used for that color, which will act as a Short stop and fixer. If the relief is very badly over-colored, it is wiser to make a new single relief or complete set as the case may be.
With any necessary adjustments made as described, we are now ready to go back to the transfer to paper.
For ease in registering, do this in the order of blue, red and yellow or red, blue and yellow.
Velvet Velox paper first fixed out without being ex-posed or washed, or the regular Eastman Imbibition Paper should be used. In either case the paper must be treated in a bath of aluminum sulphate to produce a mordant for the dye and then in a sodium acetate solution to establish the correct degree of acidity.
ALUMINUM SULPHATE SOLUTION FOR MORDANTING PAPER (KODAK FORMULA M-I)
A. Aluminum sulphate 6 3/4 oz. 200 g
Add B slowly to A, stirring well during the addition. A white precipitate is at firSt formed, but this dissolves with stirring. If a trace should remain, it can be filtered out with a rapid filter paper.
The paper is bathed five minutes in this solution, washed five minutes in running water, and then bathed five minutes in a 5 per cent solution of sodium acetate. It is finally washed five minutes in running water. It is then ready for use in the wet state.
If it is preferred to prepare a number of papers in advance, the paper may be dried instead of being used immediately. It is then soaked for twenty minutes in plain cool water before use.
Place the soaked paper face up on a plate glass, then lay a sheet of Kodaloid 5/1000 inch thick and a little larger than the paper, over the paper and squeegee firmly in all directions. This removes the surplus moisture and insures an even stretch in the paper.
Remove the Kodaloid, drain the relief a moment and rinse for about 5 sec. in 1/10 per cent acetic acid* and then place it, color image side down, upon the gelatin paper. A flat squeegee is drawn lightly over the film at first, to place in position without slipping, and then more firmly to insure good contact and expel any surplus acid solution. Over the relief film and paper another piece of plate glass is placed. The glass holds the relief and paper in good contact and keeps them from drying out during the transfer of the dye to the paper. At the end of ten to thirty minutes remove the glass and carefully lift up one corner of the paper to see if the image has completely transferred (except for a slight trace in the relief). If not, throw a little water over the relief where you have lifted up the paper, squeegee it again into contact, and leave for a longer period. Too short a contact will give a mottled appearance.
When transfer is complete, strip the film from the paper. You are now ready to superimpose the next color.
A thin piece of Kodaloid, the same as already de-scribed, is dipped into the diluted acid bath and laid over the bottom print, so that it covers all but a portion of the white margin at one end. The next color is then lifted from the acid bath and registered over the paper with the Kodaloid between. When it is accurately registered by holding down the end which the Kodaloid did not cover, the Kodaloid can be slipped out and the second print plate squeegeed firmly as be-fore into contact. It is now covered with a glass aS in the first transfer.
The third and last color is also transferred in this manner. Do not allow one impression to dry before placing the next one as the paper will shrink and affect the registration.
As soon as the final color is transferred, blot the surface of the print with a clean, dry, lintless blotter and place between two lintless blotters to dry.
Note: Some workers place the finished print in a regular No. 2 Eastman (clip type) developing hanger and dry it quickly over an electric hot plate. The quick drying maintains the sharpness of the image.
TRANsPARENCIES.-If transparencies are wanted in-stead of prints, the three stained reliefs can be examined over a light table after treatment in the dilute acid baths, and correction made as described for prints, except that the transparencies should in general be much stronger than when dyeing for a paper print. Reliefs meant for transparencies should be made slightly heavier in the original exposure than when meant for paper prints.
When correct, shake the acid solution off the face, wipe the back, and hang up to dry. Do not rinse in water before drying. Prints are mounted to suit, and transparencies bound between plain glasses or one plain glass and one ground or flashed opal glass, as preferred.
Prints or transparencies dyed with the Eastman A, B, C, dyes are sufficiently permanent to stand long exposure to diffused daylight. Direct sunlight may cause fading, but only after long exposure.
VARNISH FOR TRANSPARENCIES.—The Eastman Co. gives in its leaflet on Wash-Off Relief film a formula for varnishing the surface of the relief image for the purpose of increasing the transparency and preventing the scattering of light. The relief images are flowed with this varnish and dried before binding.
KODAK FORMULA V-I
Gum sandarac 365 gr. 25 g
The sandarac and alcohol are warmed together (not over an open flame, as the alcohol is inflammable) until the sandarac is dissolved completely. Then filter the solution through a fine lintless cloth, add the castor oil and the oil of lavender, mix thoroughly and cool before using.
The surface of the relief is flowed with the varnish, draining it off at one corner, to give a thin coating. Dry for several hours in a well ventilated room before binding.
TWO-COLOR IMBIBITION RELIEF.—TWO-COLOR imbibition relief prints can be made from Dupac by the Frederick E. Ives polychrome method as outlined by him in The Camera for March, 1933. Relief printing plates are prepared in the same manner as described above for Eastman Kodak Wash-Off Relief Process or Dyebro, and are dyed for printing as followS:
CYAN BLUE POLYCHROME DYE BATH
Water 32 oz. 1000 ccm
The Ives formula for blue toning a bromide print, over which can be cemented by use of amyl acetate a red to yellow dyed thin base relief to give a paper print, is given in the chapter on dye mordanting. Frederick E. Ives giveS full details of this method in his book "Polychrome Processes of Color Photography."
RED TO YELLOW POLYCHROME DYE BATH
Water, moderately hot 1 gallon 3750 ccm
Dyeing time five minutes. Longer time favors the greens and yellows.
CONTACT TIME.—This can be determined by practice, examining as outlined in other imbibition processes.