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Thread: PE.. Food dyes

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    PE.. Food dyes

    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?
    art is about managing compromise

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    Yes, but AFAIK, the only ones in common use were chlorophyll and erythrosine.

    They only work under carefully controlled conditions. Chloroplyll is the least effective of the two from what I understand.

    Dipping does work in some cases.

    PE

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    Struan Gray's Avatar
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    Food dyes and colours extracted from blackberry juice (and other berries) have been explored by people making dye-sensitised solar cells, a closely-related application. Their main problem is longevity.

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    Just because something is a dye does not mean that it will act as a sensitizer. Sensitizing dyes are very expensive and if there were cheap alternatives then companies would be using them.

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    Gerald, of them all, Erythrosine is quite good as long as you use the right methodology to incorporate it. It is also inexpensive due to its use in anticeptics and as a food coloring agent.

    The method of addition to an emulsion varies with the type of halide, whereas the other commonly used dyes are all added using a common method. This is the major problem with Erythrosine and I have worked out two methods of addition for it in two types of emulsion that give good sensitivity.

    I have posted the spectral response of a Br/I emulsion here that uses this dye. It is the ISO 40 film (or ISO ~200 paper negative) emulsion in another thread.

    PE

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    Thats why I suggested testing. Companies might disregard certain cheap dyes because they aren't very effecient or do not have a great shelf life. I hate to reinvent the wheel but we are stuck with the materials that are available to us.

    Quote Originally Posted by Gerald Koch View Post
    Just because something is a dye does not mean that it will act as a sensitizer. Sensitizing dyes are very expensive and if there were cheap alternatives then companies would be using them.
    art is about managing compromise

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    I based my answer on what was used commercially. I remember having to order a sensitizing dye some years ago for a phys chem class. The smallest quantity we could buy was 1 gram and this cost the university well over $100.

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    Struan Gray's Avatar
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    Perhaps I'll have to try a blackberry emulsion, just to prove a point :-)

    The purpose of a photographic dye is to capture light and then to pass the captured energy on to the halide crystal so that it can create a development center. The solar cell dyes I mentioned do exactly the same thing, but with electrode materials like titanium dioxide or indium tin oxide. The principle is the same though, and I would expect them to work to some degree with silver halides.

    But not all dyes will do this. Some hang on to the energy. Some no longer absorb effectively when attached to the receiver crystal. Some are incompatible with gelatin. Some mess up the action of developers. Some are highly poisonous. Dyes for colour negative or conventional transparency film are more specialised still, as the bit of dye left behind after it has given up its energy has to play a part in forming the colour in the processed film.

    So, the Dyes which allow you to make a medium-to-fast film with a high degree of consistency, a long shelf life and suitable fir a wide range of taking conditions are indeed very specialised chemicals, and expensive to synthesise.

    But, dyes which work well enough for a dedicated amateur who otherwise has only expensive or nonexistant options, might be cheaper, more readily available, or even growing on a bush near you.

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    Laser dyes are a little easier to get and have similar functional groups as photosensitizing dyes but tend to be pretty expensive.

    http://www.sigmaaldrich.com/Area_of_...aser_Dyes.html
    art is about managing compromise

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    Ole
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    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...
    -- Ole Tjugen, Luddite Elitist
    Norway

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