Pinatype dye structures
Capstaff's patents for his two-color process call for an "acid dye (preferably the salt of a sulfonic acid)", US 1196080; US 1315464. Only the dyes which you cited fit this description: lanafuchsin & quinoline yellow. The dyes carmine and indulin blue clearly are not sulfonic.
Pinatype dyes were used to dye the planographic matrixes over and over again. The matrixes could produce as many as twenty prints. The presence of aniline groups in indulin blue and the lack of SO3 groups in it and carmine indicate that these dyes diffuse more readily out of gelatin than dyes with more SO3 groups, groups which would have the effect of binding more substantially to the gelatin.
The Capstaff process was for "one off" assemblies of transparencies. While a dye transfer to blank paper over a period of ten to fifteen minutes would preserve the highlights, Capstaff required that the gelatin be thoroughly dried before dying, (Wall recommends drying for as long as three hours). A print surface so dried would be harder and much more likely not to absorb dye in the tanned highlights; even dyes with more affinity for gelatin such as salts of a sulfonic acid. It is possible that a wide variety of azo dyes which are salts of sulfonic acids would work in the Capstaff process. So a set of dyes suitable for DT and DB might be found.
Gaspar had a special colour seperating cine-camera made. However it took three colour-separations in high-speed succession, what nevertheless hampered filming fast moving objects. Added by the low speed of that colour film system.
Originally Posted by falotico
During Gaspar's European period hat silver-dye-bleach film was made by Gevaert.
Last edited by AgX; 01-30-2013 at 06:27 AM. Click to view previous post history.
I am aware of those processes and patents. I was pointing out that Indulin Blue is not a sulfonic acid dye and therefore was probably not one that Captstaff really used. I also point out that a DB and a DT system could be built using the same dyes if they were all from the Azo dye family.
A multi-use set of Azo dyes both for DB and DT would be very convenient. It might also be possible to combine the two processes: develop with a tanning developer, let the dye transfer into the whole matrix approximating the correct tones, and then bleach out the highlights.
From the language of the patents Capstaff seems to indicate that he uses only one dye per color. It also seems that his images from Capstaff Kodachrome were all assemblies requiring silver halide emulsions on transparent bases. I recall seeing a two-color portrait of George Eastman(?) from the 1920's which was published in the Time/Life book on photography called "Color", (1978). That gives some idea of the color values; the warm tones were somewhat orange. Looking through samples of dyes available at that time with the correct chemistry (acid dyes which form salts of sulfonic acids) it might be possible to rediscover the dyes that Capstaff used. The Colour Index gives structure, hue, lightfastness and date of discovery.
Capstaff invented two versions of DT: the first tanned the highlights with a bi-chromate bleach in the standard manner; the second tanned all the gelatin with ferric chloride and tartaric acid and then de-tanned the lowlights with a UV light image. I assume each version used different dyes. IDK which version the portrait in Time/Life "Color" used. I would love to see a Capstaff DT in the flesh.
I have seen examples of European Gasparcolor on Youtube. Gaspar moved here to California before the war and lived in Beverly Hills. He donated all his papers to UCLA and these are held by Special Collections. I wonder if he had Gevaert coat his films after the war. IDK who did that work for him.
All of the Capstaff work may now be at the George Eastman House.
As for a single dye set for both DB and DT, that is my goal as then you can match the prints using different methods. And, DB and DT materials are rather easy to coat yourself. None are in production at this time, but Jim Browning has posted a formula for the Matrix Film, and I have suggested elsewhere on APUG that a hardened version in a multilayer film or paper might be used for DB.
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Jim Browning posts the three dyes he uses for DT along with his formula for matrix film at http://www.dyetransfer.org/. These dyes are:
Acid Blue 45- C.I. 63010
Acid Red 80- C.I. 69215
Acid Yellow 11- C.I. 18820
Only Acid Yellow 11 appears to be an azo dye, but it might be suitable for DB.
All the structures I can find for Chicago Blue are diazo (cf. Chicago Sky Blue 6B- C.I. 24410); the dye for the DB emulsion in "Photographic Emulsion Making" Solantine Pink is also diazo, C.I. 25380. Do the Chicago Blue or the Solantine Pink in this DB method transfer?
If I can get out to Rochester, NY I would like to see what I can at the George Eastman House.
Jim has used Solantine Pink and Solantine Yellow, as have I, for DB and for DT. The pink is a bit short but is rather like the old magenta in Ektacolor 70 paper.
So, the pink and the yellow both transfer and work with DB. What we lack is good information on a cyan, and we may need a better magenta.
Isoelectric point of gelatin and dye absorption
Isoelectric point of gelatin and dye absorption. I came across a patent which describes the use of tanning developers to change the isoelectric point of gelatin and thereby make the developed image less able to absorb acid dyes. The invention is by David Dean and Robert Houck and they assigned the patent to EK: US Patent 2529922 (1948). They worked with dye-transfer (DT) relief matrix material which they exposed to an image and then developed in a tanning developer, either pyrogallol or hydroquinone. Ordinarily the gelatin has an isoelectric point at pH 4.7, but the oxidation products of the developers lower the isoelectric point of the gelatin composing the image to about pH 4.0 and leave the non-image areas of the gelatin at pH 4.7. Acid dyes which are dissolved in aqueous solutions at pH 4.7 will be absorbed by the non-developed gelatin, but will not be absorbed by the developed gelatin with the lower isoelectric point.
The principle has to do with the effect of acid/alkali solutions on the gelatin. The isoelectric point (IEP) is defined as the pH of the gelatin at which the positive charges in the gelatin are equal to the negative charges. If the gelatin is immersed in a solution of LOWER pH than the IEP--that is, a more acidic solution--then the gelatin will absorb more H+ ions than OH- ions, and consequently the gelatin will acquire a net positive charge. This positive charge will attract the negatively charged molecules of an acid dye. Acid dyes are anionic dyes. If the gelatin is placed in a solution whose pH is HIGHER than the IEP, than the H+ charges will be fewer than the negative charges in the gelatin. Consequently the gelatin will have an overall net negative charge which will repel the negative charges of the acid dye anions. (However, the gelatin will in this case attract molecules of BASIC dyes, which are cationic and positively charged).
Dean and Houck in their 1948 patent summarize these principles: if the IEP of the gelatin has a HIGHER pH than the solution containing ACID DYES, than the gelatin will absorb ACID DYES; if the IEP of the gelatin has a LOWER pH than the solution containing BASIC DYES, than the gelatin will absorb BASIC DYES; otherwise, the gelatin will not absorb the dyes. Dean and Houck used their invention to produce dye-transfer prints on a blank gelatin-coated paper.
CAPSTAFF AND PINATYPE PROCESSES. Both the Capstaff two-color process and the Pinatype dye-transfer process depended on using dichromate ions to harden gelatin. This formed the basis for selective absorption of acid dyes. In the Capstaff system, the photographic plate was exposed to the proper color record, then developed, bleached, hardened and dried. Finally it was placed in a weak acid dye bath and the dye would not be absorbed in any place where there had been a silver image. In other words, the dye would not be absorbed where the gelatin was hardened by reduced dichromate ions. But the dichromate reaction also lowers the IEP of the gelatin. I believe that the changed IEP also repels acid dyes in conjunction with the effect of hardening the gelatin--which hardening would make the acid dyes harder to absorb.
Similarly, in the Pinatype process, dichromate ions also harden the gelatin, but it this case through the action of exposure to UV light under a negative. The acid dye solution is not absorbed by the hardened parts of the gelatin. The dichromate matrix is then pressed onto a blank and the dyes transfer from the untanned portions onto the print forming a DT image. I suspect that here too there is a lowering of the IEP which repels the acid dyes.
I am aware that today isoelectric points are routinely analyzed in dye diffusion processes. I mention it here because I don't think that IEP changes have been considered as an aspect of the Capstaff or Pinatype processes. In the case of Pinatype this is because the Pinatype process was developed before the pH scale was invented. In the case of the Capstaff process, interest faded before IEP changes were understood very well in colloid science. As far as I know it was never considered as a cause of what was called in the 1920's "the Kodachrome effect."
Well, there are some problems here that were not fully understood or disclosed at the time of this patent.
IEP affects swell. In fact, IEP defines the minimum swell of a given gelatin and thus the point at which a minimum amount (or exact amount) of dye is absorbed. Change the IEP and swell changes. In fact, this trend goes counter to some of the points of the invention, but nevertheless, this change in pH was used to "bleach" dye from the mat reducing density or contrast.
Last but not least, you only discuss bone gelatin it appears, but at that time, they also used pig gelatin which has an IEP of about 9 and therefore this gelatin reacts totally differently to the conditions of the patent than bone gelatin.
I am not saying that they are incorrect, nor am I suggesting that this work is not useful, I am suggesting that there is a lot more to consider and a lot more going on than the patent suggests.
Capstaff's two-color Kodachrome process.
P.E., this is off subject a little but some of National Geographic's earliest color pictures were made with a color process that, I once read, used dyed starch granules. Have you ever heard of this?...regards
Originally Posted by Photo Engineer