Color Photography - Chromatone Process
( Originally Published 1938 )
THIS process, introduced in 1935 by the Defender Photo Supply Company, Inc., is a method of using a collodion stripping paper manufactured by the Defender Company and tricolor toners developed by Francis H. Snyder and Henry W. Rimbach of New York City.
Chromatone procedure differs from all existing processes by forming the three component colored images on thin collodion stripping film ; it bears some similarity to mordant and basic dye processes in that a silver positive image is used as the basis from which the colored image is formed. In the case of Chromatone, the Defender Company supplies the toning solutions that convert the silver images into the respective yellow, magenta and blue-green images.
From three separation negatives, such as have been described for other processes, a set of prints is made, preferably by projection, on Chromatone print paper. This paper is now supplied in regular and soft grades.
Chromatone prints can be assembled with the emulsion or collodion side up. The merits of these methods are discussed later. If mounted collodion side up, printing should be done from the reverse side of the negative instead of the front.
PRINTING.—Since the effect of toning operations to follow is to alter slightly the relative strength of the black and white positive, the following procedure is recommended. By test ascertain the exposure necessary to produce a well balanced grey scale on the three black and white prints.
From the green record negative, produce a print of normal quality for the magenta toning. Expose the print to be toned yellow 25 per cent longer than the time needed to match the neutral scale of the accept-able magenta print. Expose the print to be toned blue-green io per cent longer than the time required to match the neutral scale of the magenta print.
The result should be a normal magenta toner print, overexposed yellow toner print, and slightly full blue toner print.
The three prints should be developed at the same time in fresh developer. Since the emulsion is fast, similar to Velour Black, it should be handled in the regular series OA bromide safelight. A short stop of acetic acid will remove the surplus alkali, before placing the print in the fixing bath.
Fixing is carried out in the usual manner. While the maker's instructions mention a standard fixing bath in which alum is used as a hardening agent, some workers prefer a hypo bath with potassium metabisulphite only, as the alum bath sometimes leaves a scum on the print.
After five to ten minutes in a fresh fixing bath the print is transferred to the washing tray. During the fixing, or early in the wash water, the collodion emulsion will leave, or can be stripped from, the paper sup-port. The paper is then thrown away. Wash about twenty minutes in running water.
If the collodion image feels slippery at this time, it can be hardened for a minute or two in a 10 per cent solution of formaldehyde.
Each print should be marked in some way when made, so that you will know the proper color later. Water-proof India ink can be used for this purpose.
For those troubled with scum-like marks in toning, especially with the magenta toner, the use of the following fixing bath will often eliminate this trouble.
Potassium thiocyanate 100 g
The foregoing formula can be used in place of the standard fixing formula listed in the formulas at the end of this chapter.
TONING.—The second step is the toning of the three black and white prints. After the prints have been thoroughly fixed and washed, the remaining steps can be carried on in white light.
In toning, glass or perfect enamel utensils should be used, if possible. Avoid use of metal, since it tends to contaminate the toning solutions.
The stripped-off emulsions intended for the blue and red images are placed together in a tray, and the working solution of the red and blue toner A, made up as outlined in the formulary, is added. Care should be taken that the films are well covered by the solution. It is advisable to turn the prints over repeatedly and to rock the tray to remove any bubbles which might be under the film.
A swab of cotton or wide camel's-hair bruSh is very useful to prevent uneven toning. Brush or swab the prints continually during the toning operations. The brush should be thoroughly washed after using. The above toning operation takes about fifteen minutes to perform, at which time the print will appear as a greenish brown image. If there is any trace of the black silver image remaining, treatment in this bath should continue until it disappears. Keep the solution around 65° F. (18° C.), never above 70° F. (21° C.).
After the above action is complete the prints should be washed in not less than five changes of water, allowing them to soak thirty seconds in each change. This is recommended in preference to the usual fifteen minutes in running water.
It is very important that the hands be kept clean at all times in order not to contaminate one solution by transferring another solution to it.
After this washing, the red image is placed in the red toner B and allowed to tone for about ten minutes. A little longer time in this bath does no harm, but a 10-minute immersion is usually sufficient. Pour off the solution for future use and immerse print for three minutes in a standard hypo solution (see formulary). Wash for fifteen minutes in running water. The red print is now ready for assembling.
The blue image is immersed in the blue toner B and allowed to remain for about ten minutes, after which the toner is poured off for later use. Immerse the print in a weak hydrochloric acid solution for about one minute. Use one part dilute solution with two parts water (see formulary). Wash the print thoroughly in running water for about ten minutes, and transfer to a tray containing standard hypo solution until greenish tones have changed to blue. Wash for twenty minutes and print is ready for assembling.
The yellow toner solution (yellow toner A) comes in two solutions and must be made up as directed in the formulary. The print to be toned yellow is immersed in this solution for fifteen minutes. Pour off the toning solution into a graduate and add 10 ccm (3 drams) to every 50 ccm (2 oz.) of working solution and mix thoroughly. Wash the print for one minute in running water and return to the tray containing the toning solution. This operation should be done quickly and the tray rocked vigorously for one minute to pre-vent streaking of the yellow image. Let the toning action continue for another three minutes, discard the toning solution, and wash print for two minutes in running water. Immerse print for one minute in a solution of one part standard hypo solution, three parts water. Do not keep print too long in this solution, as the yellow image is slightly soluble at this stage and highlight detail may be lost. Wash print for not less than twenty minutes in running water. Upon completion of the washing immerse print for two minutes in tray containing yellow toner B. Wash for twenty minutes in running water and print is then ready for assembling.
ASSEMBLING.—The next step is assembling the three toned images on the Chromatone backing paper.
Soak a sheet of Chromatone backing paper in water. Lay backing paper gelatin side up on a clean ferrotype tin or any smooth hard surface. The yellow toned image is placed emulsion side down on the backing paper and squeegeed firmly into place and allowed to remain for a few minutes. The red image is then placed on top of the yellow, pushed carefully into register.
Squeegee lightly and check the register, adjust if necessary and, when registering is complete, squeegee firmly into place. If any difficulty is encountered when registering, the red image may be peeled off carefully, remoistened and registered again. It will be found easier to register the red and yellow images if viewed through a light blue filter.
The blue image is then superimposed upon the other two as described above. This completes the color print, all prints emulsion side down.
When mounted this way the prints have a high gloss which is not easy to retouch. Chromatone prints have reasonably tough emulsion surfaces, which with care can be mounted emulsion side up.
RETOUCHING.-Use moist transparent water colors. If the print is assembled collodion side up, spotting and retouching should be done while the print is still moist. If the print is assembled emulsion side up, spotting is best done on the dried print.
The print is now allowed to remain in the air for about ten minutes, until the surface dries to some extent. Trim the print till the collodion edges are flush.
Place the trimmed print on a rigid, hard water-proofed material. Masonite tempered hard board is recommended for this purpose. The masonite board should be at least one inch larger on all sides than the print itself. A one-inch strip of gummed tape is moistened and the damp print is fastened to the board by this tape overlapping the print by 3/16-inch on all sides. The print will dry rapidly, stretched abSolutely flat. It can be detached from the board by cutting the tape alongside the edges of the print.
A special backing paper with a thin gelatin coating on the reverse side will help prevent curling. After the Chromatone print is assembled on this special paper, the wet print is turned over on its face and a piece of cellophane (not the waterproof variety) is first soaked in water and is then squeegeed firmly on the back of the print. The print is turned over and bound with the gummed tape as mentioned before. When dry it is cut from the supporting board.
The surface appearance of Chromatone prints can be much improved by sponging with a 4 per cent water solution of gum arabic, and if necessary, a final touch of matte lacquer.
The print can now be trimmed to size. The backing board can be cleaned for further use by soaking it in warm water for a short time, at which time the gummed paper can be removed. The board is then ready for future use.
REDUCING THE COLORS.—The red image can be reduced by placing print in dilute hydrochloric acid A (page 107), one part, water fifty parts. Wash thoroughly when sufficient reduction appears to have been obtained. The same solution will reduce the yellow, but its effect is to cut out faint detail before reducing the image as a whole.
The blue can be reduced by immersion in
Red toner B 1 oz. 20 ccm
until uniformly purple all over. Then place in one part dilute hydrochloric acid, twenty parts water, until color returns. Wash thoroughly. By this treatment the resulting color inclines somewhat to the greenish side, which can be corrected by immersing again in hypo and re-washing.
COLOR IMPROVEMENT BY MASKING.—The balance of brilliancy of greens and reds can often be consider-ably improved by a method first suggested by Mr. H. Murray of Eastman Kodak Co. The principles of this masking method can be easily applied to the Chromatone Process in the following manner:
Make three thin positives by contact from the red record negative (blue-green printer) on a slow plate such as Seed 23. The positives should be approximately one-third the density range of the negatives. (This may be checked roughly by superimposing the three masks and comparing the neutral scales, provided one has been included in the picture.)
When using this method, negatives should be developed about 33 1/3 per cent longer than normal if they are to have enough contrast after masking to print successfully. Normal negatives can be carefully intensified.
One mask is now registered and bound up with each of the separation negatives, Scotch Tape being used to fasten the films to the glass.
DEVELOPMENT DATA.-6-D developer, used in tray. Time of development—2 1/2 to 3 minutes. Temperature 700 F. (21° C.).
Conversely, if negatives are too hard to make good Chromatone prints, excellent prints can often be made from them by employing the Masking Method.
FORMULAS: DEVELOPERS FOR CHROMATONE PRINTS
Standard Formula 1—NORMAL CHROMATONE DEVELOPER
This is the formula that, with normal negatives, will give correct results in the black and white positives for Chromatone prints.
Water 40 oz. 2000 ccm
It has been explained that negatives for color work cannot be intensified or reduced, but the effect of such treatment can be obtained by using soft and hard gradation developers with the standard Chromatone print paper. Mere variation of the proportions of metol, hydroquinone, carbonate, Sulphite and bromide are practically useless when compensation is desired for negatives which are too hard or too soft. The following formulas, if used with the correct time of development, will give prints with blacks of the same order of brilliancy as the standard developer. They do not flatten the picture or produce excessive contrast.
Solution: Use one part stock to three parts water. Develop three to four minutes at 700 F. (2I° C.).
THE CHROMATONE PROCESS 105
Vigorous Formula 3—VIGOROUs CHROMATONE DEVELOPER
(For good prints from soft negatives)
Water 32 oz. 1000 ccm
Water 32 OZ. 1000 ccm
Use equal parts A and B. Develop five minutes at 70° F. (21° C.).
Regular Formula—ACID FIXING BATH
(For Chromatone black and white prints. Do not confuse with "Standard Hypo Solution," page 107)
Water 64 oz. 2000 ccm
Dissolve chemicals one at a time, in the order given, before adding the next ingredient. To avoid unfixed prints, renew frequently. The use of boric acid in the hypo bath prevents the forming of irregular patches of scum, invisible when wet, due to hard water.
Caution: This fixing formula containing boric acid does not discolor or froth in use and there is no visible indication of its exhaustion. It is, therefore, important to change frequently, so that any chance of imperfectly fixed prints can be avoided.
THIOCYANATE FIXING BATH
Potassium thiocyanate 3 1/2 oz. 100 g
This fixing bath is indicated when speed is necessary, since it is not imperative that the washing be very thorough before toning, as traces of this solution will not interfere with toning operations.
WORKING SOLUTION FOR CHROMATONE COLOR PRINTS
(Sufficient quantity for toning 5 by 7 prints)
RED AND BLUE TONER A—WORKING SOLUTION
Water 1 oz. 25 ccm
This solution does not keep well when mixed, and only sufficient should be prepared for prints in process.
YELLOW TONER A—WORKING SOLUTION
Yellow toner A-No. 1 1 oz. 25 ccm
Add No. I to No. 2, stirring gently until any precipitate that may appear is completely dissolved. This solution does not keep well when mixed and only sufficient should be prepared for the prints then in process.
After toning for ten minutes, pour solution into graduate and add 3 dr. or 10 ccm of standard hypo solution (below). Wash the film in running water for two or three minutes, return it to the tray and pour the solution back on the print and continue toning for another ten minutes.
Red toner B, blue toner B and yellow toner B are used without dilution or addition. Red toner B and blue toner B can be used more than once, provided great care is exercised to prevent contamination.
Note: The quantity of materials supplied with the Chromatone package is just sufficient to tone the number of sheets of Chromatone photo print paper sup-plied. In planning on making one finished 5 by 7 print only, use 25 ccm of red and blue toner A, and 25 ccm of yellow toner A, as given above. Of red toner B, blue toner B and yellow toner B, use sufficient solution to cover the print. The red and blue toner solutions B may be returned to the bottle for further use; the yellow toner B is discarded.
ADDITIONAL WORKING SOLUTIONs.—The following solutions, although furnished in the Chromatone photo print package, may be made up by the user as desired:
A. Dilute hydrochloric acid
Hydrochloric acid C.P. 16 oz. 500 ccm
B. Standard hypo solution
Granular or rice hypo 2 1/4 OZ. 70 g
Wherever the text refers to standard hypo solution, this is the formula that must be used. A bath containing acid or alum will bring complete failure.
C. Standard ferricyanide solution
Potassium ferricyanide 1/2 oz. 11 g
These solutions should be kept in well-stoppered glass bottles for convenient use.
The potassium ferricyanide does not keep well in solution. It keeps a little better in the dark, but should not be kept for more than a few days.