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Thread: PE.. Food dyes

  1. #11

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    This one is right out of "Photographic Sensitivity",
    https://www.sigmaaldrich.com/catalog...il/SIAL/173738
    art is about managing compromise

  2. #12
    Struan Gray's Avatar
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    Quote Originally Posted by avandesande View Post
    Laser dyes are a little easier to get and have similar functional groups as photosensitizing dyes but tend to be pretty expensive.
    Caution: if you're buying laser dyes without experience of using them, please study the material data sheet and any manufacturer safety recommendations. Many of them are poisonous, carcinogenic, or both. We don't let PhD students handle them without special safety training over and above the usual laser safety course.

  3. #13
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    Silver halide sensitizing dyes are similar to the dyes used by the human eye to affect color imaging. The big difference is that the dyes adsorb to the surface of the silver halide crystal. Of course, there are dyes that form direct, light sensitive salts with silver to give a material that is light sensitive in a given region of the spectrum.

    The best dyes are quite complex organic molecules and very expensive to make. Many of them are very toxic to animal life but are used at such tiny levels and decompose so quickly during processing, that they pose no problem. They also have great difficulty entering the animal body due to their very nature, but should be handled with care.

    Erythrosine is an exception, being very low in toxicity.

    The color of the dye is adjusted during synthesis by changing the number of CH=CH groups in the chanin between two large ring structures, the more, the further towards cyan the dye becomes until it becomes an infra red dye which is rather black. Dyes are the opposite in color to the portion of the spectrum that they sensitize the emulsion to.

    I know of no azo dye that is a sensitizer for silver halide. These are dyes formed from N=N moieties.

    The foremost researcher into this topic at Eastman Kodak is Paul Gilman. He 'wrote the book' so to say.

    PE

  4. #14

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    Quote Originally Posted by avandesande View Post
    PE, has anyone done comprehensive testing of food dyes for sensitizing activity? I thought an easy way to do this would be to get some ortho film, dip it in the dye and let it dry out...and epose. What do you think?
    Here in the US "McCormick Assorted Neon Food Colors" has 4 dyes in the kit. One of the bottles is FD&C Red #3 and from my research on the net is erythrosine.

    Hope this helps,
    Ron

  5. #15
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    You are correct, but you don't know several things about it.

    1. Concentration - this is critical when it comes to adding to the emulsion.

    2. Other ingredients - again, critical.

    PE

  6. #16

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    Quote Originally Posted by Photo Engineer View Post
    You are correct, but you don't know several things about it.

    1. Concentration - this is critical when it comes to adding to the emulsion.

    2. Other ingredients - again, critical.

    PE
    Hey PE. Thanks for your response.

    I guess that the easiest and most inexpensive way to test the effectiveness of this dye is to try it in an emulsion then check for ortho sensitivity and possible negative side effects.

    Ron

  7. #17
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    Quote Originally Posted by rongui View Post
    Hey PE. Thanks for your response.

    I guess that the easiest and most inexpensive way to test the effectiveness of this dye is to try it in an emulsion then check for ortho sensitivity and possible negative side effects.

    Ron
    Yes.

    Testing is difficult though. You need a spectrosensitometer or multi color step wedge.

    PE

  8. #18

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    Quote Originally Posted by Ole View Post
    It would be interesting to know what dyes Herr Dr. Vogel tried and rejected about a century ago, before he finally managed to make an orthochromatic emulsion...
    Vogel started his experiments with Korallin. Later, he introduced Eosin and Azaline (mixed of Cyanine and Chinolin red).
    The use of Erythrosin goes back to Eder.

  9. #19
    Struan Gray's Avatar
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    I did some digging in the (online) library, and came up with the attached text from a history of Ilford published by G. B. Harrison in the Proceedings of the Royal Society in 1953.

    W. de W. Abney (later "Captain Abney", later still "Sir William Abney") published several interesting papers in th Proc. Royal Soc. in the 1880s and 1890s. He says that analine dyes were tried in collodion emulsions, but were not very successful. He states that the best dyes were the ones most easily bleached (which makes sense from a modern understanding of dye sensitisers). The analine dyes were of course famous for their colour fastness.

    Finally, the best explanation I have yet read of how development centres form in a halide crystal and how a dye molecule contributes to the process (as well as what reciprocity failure is and how it occurs) turned up in a beautifully-written and classic paper by Gurney and Mott. Recommended if you have access to a research library:

    "The theory of the photolysis of silver bromide and the photographic latent image." R.W.Gurney and N.F. Mott. Proc.Roy.Soc. Vol 164, No.917 (Jan 21, 1938), pp151-167.
    Last edited by Struan Gray; 05-27-2008 at 05:01 PM. Click to view previous post history.

  10. #20
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    Struan;

    The Gurney and Mott work is a classic well known at Kodak. When we are first hired at Kodak in research we take a very long course in photographic science and engineering, going to regular classes with homework along with our normal job.

    We have a huge set of notebooks that teach every phase of this, and the work is accompanied by a lab where we first do hand coatings and then machine coatings. We do color and B&W both.

    We used to call it "Ding Dong School".

    This two volume set has never been published for obvious reasons, but part of it is in Mees and James and part is in Haist. These are the 'unclassified' parts.

    The classified parts contain (among other things) page after page of sensitizing dyes, their properties, their spectra, the best mode of addition, what types of grains to use them on. It resembles the tables in Mees and James, but is more extensive. Gurney and Mott are prominently featured in the section on sensitization. The current version on dyes was written by Paul Gilman.

    PE

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