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  1. #51

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    More on Pinatype dyes

    Apologies for double-posting the previous text. Friedman in "History of Color Photography" in the first two pages of Chapter 26 gives a good discussion of pinatype dyes; he even addresses the 1911 article from Brit. J. Phot. vol. 58. He mentions specifically the natural dye carmine, among other types, and he gives a broad discussion of the chemistry of suitable dyes.

    In particular "sulphonic groups", (which I take for "SO3" groups), caused the dye to stay in the gelatin; while "nitro groups" (NO2) caused the dye to wash out easily. It seems likely that many azo dyes with a SO3 group could be good candidates for pinatype dyes.

  2. #52
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    You may have missed this but the terminology is connected to the Pina Cryptol family of dyes. It has been found that more than one SO3- group is useful in making the dye fast in gelatin and even mordants are used.

    The archetype dyes of this nature today are the Solantine class (Solantine Pink and Solantine Yellow) and then there is my old favorite Chicago Blue. A mix of the pink and yellow will probably satisfy the Capstaf short wavelength dye, and Chicago Blue itself will supply the long wavelength dye.

    The PINA designation is no longer used.

    PE

  3. #53

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    Acid dyes

    I assume that these are the same dyes that you recommend for the dye bleach color emulsion described on page 171 of your book, "Photographic Emulsion Making, Coating and Testing".

    Looking at internet images of the structures, Solantine Yellow (C.I. 13950) appears to be an azo dye with two SO3 groups; Solantine Pink (C.I. 25380) appears to be a diazo with four SO3 groups and two aniline groups. The dye called Chicago Blue appears to refer to two structures, Chicago Blue 4b and Chicago Sky Blue. From what I can tell it also has azo groups with four SO3 groups. I can't find a C.I. number for Chicago Blue. All this is consistent with acid dyes which can be reduced and made colorless in the dye bleach process outlined.


    Their diffusion properties are interesting. Do they stain untanned gelatin and not tanned gelatin? Has anyone tried staining a dry gelatin tanned matrix? Could the diffusion rate be regulated by Ph?


    It is surprising to see the great interest people have shown in Capstaff's two color photography. Incidentally, I am looking forward to getting volume two of "Photographic Emulsion Making" and learn more about color emulsions. I hope you're not being threatened with being chained in the barn until you finish writing it.

  4. #54
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    These dyes would probably work well for both Dye Bleach and Dye Transfer. However, Solantine Pink is a bit short as is Chicago Blue, but I have made good DB coatings with all 3 and reasonably good images. That is why I think that if they transfer, they would work well with a 2 color process. You need an orange and a blue approximation.

    They are similar to DT dyes, and should transfer once the emulsion is tanned. I'm not sure though.

    I am still looking at options. The barn and chains or another book. With one, I would hop I get fed, I know I have a "room". With the other I have to pay for my own keep. Decisions, decisions!

    PE

    PE

  5. #55

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    Well, I'm certainly looking forward to another book. In the Technicolor DT process the dye solutions were loaded with acetic acid, but the Capstaff patents don't mention this. Neither does Capstaff mention temperature, although this was critical in Technicolor DT.

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    I suggest experimentation.

    PE

  7. #57
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    Thanks falotico for bringing this topic back up. It's very interesting about Mannes/Godowsky and drying the film before the diffusion process. That's an interesting point...

    I think the strength of the Capstaff process is in the dye colors. I've seen them and I don't think that a mixture of typical CMY dyes would really do the trick. Of course you can make any color (in theory) with CMY, but in dye-imbitition systems the dyes cannot be mixed and expected to give a neutral scale since each dye's contrast curve is related to its own particular pH. So although you could match the color with a mixture of CMY; a mixture probably wouldn't work in the process.

    So the trick is to find 2 dyes, with the right "pina" properties and the right colors. An experienced colorist could probably look at examples of the two dyed members of a 2-Color KR and give some suggestions for acid dyes that may work.
    If you are the big tree, we are the small axe

  8. #58
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    You need an orange and a blue!

    And at the time it was beautiful, but with today's eyes, the look rather poor.

    The drying step was to assure that diffusion started the same each time.

    PE

  9. #59

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    Mixing dyes

    Capstaff in his patents, see US 1315464 issued 1919, calls for "an acid dye (preferably a salt of a sulfonic acid)". I take this to mean the molecule has SO3 groups. These SO3 groups would cause the dye to bind with the gelatin. A wide variety of dyes were available to him at that time and probably there was one of the proper shade of orange and one in the proper shade of green. However, it is certainly possible that the 1920's Kodachrome used a mixture of dyes for either the orange or the green or both.

    Dye transfer processes often used a mixture of dyes to form one of the fundamental shades. Technicolor mixed its dyes both to form the cyan and the magenta, IIRC.


    Cinecolor, although not DT, famously used a mixture in its two color process for the red tones. The blue tone would be a silver image on one side of the film which was converted to a cyanotype (Prussian blue) by ferric cyanide. But the red would consist of a maroon dye and an orange dye which attached to a mordant created out of the silver image. Red objects would look natural. However when a yellow object was photographed it left a less dense silver deposit in the image and only the orange dye adhered to that. Thus yellow objects appeared orange. The two dyes would indeed express in unequal ratios depending on the exposure, but it had the effect of producing a separate tone for the yellows. Some people said that Cinecolor was a two and a half color process instead of three.


    All the DT processes offered considerable post-exposure latitude to the lab. While the results might not meet the high standards of the experts at EK, they are a form of art in their own right, IMHO.

  10. #60
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    I must respectfully disagree with my potentate Ron... the Capstaff's look absolutely beautiful to this day! There are a collection of 8x10 glass portraits and still lifes at GEH and they're stunning; legitimately.

    2.5 colors; that's an interesting way to look at it. I am surprised that Technicolor would have used a mixture of dyes for the reasons above, but it's certainly possible that two dyes could be found with a close-enough pH/contrast relationship. Kodak DT though, definitely only used 1 dye for each sep.
    If you are the big tree, we are the small axe



 

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