What dyes? I can't think of any OTOMH. That is why Utocolor and things like it have failed.
PE
PE
Photochromic or photoreactive autochrome
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I'm not sure if I totally understand what your proposing. Firstly immiscuable in water would mean I think droplets of oil soluble dye in a water soluble solution. The problem is partially contamination. Though the droplets are not soluble in the solution they are solvable amongst themselves. Your relying on surface tension to keep them pure and emulsifiers to keep then in solution without separating out. Then you've got to get whatever chemistry you are using to fix (make less sensitive to light after the exposure) or develop the image (complete and image formation) through both the water and oil soluble portion of the emulsion without ruining the structure. You also have to arrange it so that for example the cyan chromogenic component is reacting to red light and only red light when forming cyan dye. Usually these chemicals natively are sensitive to a range of light and color filters of some sort need to be used.
Here is one idea. Select dyes that fade rapidly - many simple dyes do. Then, select a metal salt that can complex with the dye set. This might be Calcium, Magnesium, Aluminum, Iron or Nickle as examples. Complex the dye and the stability goes up. You might even be able to use a mordant.
The problem is that any dye I know that does this, pretty much changes hue when complexed or mordanted. This is a major problem. If you pick dyes that have the correct hue mordanted, they have the wrong hue when subject to fade for imaging.
AFAIK the dyes for UTO color have not been published, but I've never made a search beyond some simple queries.
PE
The problem is that any dye I know that does this, pretty much changes hue when complexed or mordanted. This is a major problem. If you pick dyes that have the correct hue mordanted, they have the wrong hue when subject to fade for imaging.
AFAIK the dyes for UTO color have not been published, but I've never made a search beyond some simple queries.
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I suspect UTO gave poor results. The contemporaries I read were not all that impressed with it but to be fair they were comparing it to a autochrome original they contact printed from. I've not seen the original dye list but Im not sure there were all that many choices in the negative color space. An olive was synthesized in 1856 and uto came out in 1907. Here is a rough history of dye synthesis assuming they were synthetic - http://www.straw.com/sig/dyehist.html
Maybe alizrin yellow, and fuchsin (magenta). I know absolutely nothing about dyes (another study topic) and don't know what cyan was available to someone in the early 1900's but it doesn't seem like there were many choices back in this era.
Maybe alizrin yellow, and fuchsin (magenta). I know absolutely nothing about dyes (another study topic) and don't know what cyan was available to someone in the early 1900's but it doesn't seem like there were many choices back in this era.
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P.S. I just read "Experiments with the Bleach-Out Process" from a 1907 edition of the Colour Photography Supplement by the British Journal of Photography. It doesn't list the original dyes but gives lots of clues on the process including the sensitizer (anethol and possibly persulphate) which caused the dyes to become more fugitive. The resulting reds came out with too much orange for instance. Also the dyes were embedded in collodian (cellulose nitrate dissolved in ether and alcohol) not water.
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J. S. Friedman in his "History of Color Photography" has a very good discussion of the Utocolour system and the chemistry of the relevant dyes. The process is called "Bleach Out Photography" and is chapter 28 in his book. It is available online, here is the link:
https://archive.org/details/historyofcolorph00frierich/page/494
Friedman had a Phd in organic chemistry and he is a very good source for dye chemistry. If you are interested you should do your best to plow through his book.
An earlier researcher E.J. Wall also discusses bleach-out photography in his book "Practical Colour Photography". Here is the link:
https://books.google.com/books?id=Y...e j wall practical colour photography&f=false
Wall has his discussion in Chapter XIII. The three dyes he mentions are methylene blue, erythrosine (magenta), and auramine (yellow)--which were probably the dyes used in Utocolour.
The dyes you mention are probably not the ones used. The film would fade at almost the same rate as these three dyes. And they are not very stable in the long term, nor do I know any way to stabilize them. I read the Friedman book years ago and cannot remember the details, but I don't remember anything about Utocolor in detail. I'll check that out tomorrow if I have time.
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Thank you so much ! ! I just ordered a copy of Friedman for my library. I might have to try this out myself now when Christmas break comes and I've got some more time. Thanks for finding a reference !
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Are the dyes unstable normally because of light, or because of oxygen/atmosphere? Maybe collodian was used more as a partial sealant than as a carrier.
The dyes mentioned fade slowly, not rapidly, and that is why I feel that they are not usable in a Utocolor type material. Of course they are not as stable as modern dyes, but they don't fade rapidly. Their biggest enemy, at a guess, would be the UV in sunlight.
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Utocolour depended upon incorporating a chemical which would accelerate the photo-fading of the respective dyes. Since the dye which was sensitive to blue light absorbed the most energy, it would fade the fastest. So to equalize the rates of fading a less efficient chemical was used as an accelerator for this dye (which would be the yellow dye); while a more efficient chemical was used for the other dyes, the magenta and the cyan.
When the dyes are struck by the correct color of light they fade because they absorb electrons. In chemical terms they are "reduced". This reduction reaction transforms them into colorless compounds called "leuco" forms. To speed the fading a reducing agent is added to the emulsion as an accelerator. One such accelerator is thiourea. It was found that a form of thiourea was even MORE efficient at promoting photo-fading. This form is allylthiourea.
So thiourea was added to the yellow layer; allylthiourea was added to the magenta layer; and an even greater concentration of allylthiourea was added to the cyan layer. In principle then the dyes would fade at the same rate. Once the exposure was complete the photograph was washed to remove the accelerators and the leuco forms of the dyes.
When the dyes are struck by the correct color of light they fade because they absorb electrons. In chemical terms they are "reduced". This reduction reaction transforms them into colorless compounds called "leuco" forms. To speed the fading a reducing agent is added to the emulsion as an accelerator. One such accelerator is thiourea. It was found that a form of thiourea was even MORE efficient at promoting photo-fading. This form is allylthiourea.
So thiourea was added to the yellow layer; allylthiourea was added to the magenta layer; and an even greater concentration of allylthiourea was added to the cyan layer. In principle then the dyes would fade at the same rate. Once the exposure was complete the photograph was washed to remove the accelerators and the leuco forms of the dyes.
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Just chiming in here again, does page 702 from: http://www.processreversal.org/public/text/Glafkides_photographic_chemistry_vol_2_compressed.pdf
help at all? (chapter xxxiv)
@falotico All 3 dyes you have mentioned are there.
@Photo Engineer The stabilization and sensitization methods are mentioned as well, I think
help at all? (chapter xxxiv)
@falotico All 3 dyes you have mentioned are there.
@Photo Engineer The stabilization and sensitization methods are mentioned as well, I think
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Preservation of the dye layer in a UV-blocking varnish overcoat would leverage modern technology to help overcome this legacy issue (thinking glass-plate substrate).
That might help. IDK. We don't know much about Utocolor currently.
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Thank you for presenting this book. It is very interesting.
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I'll check it out when I get back home. A quick check revealed all of the dyes existed by the 1890s or so, meaning they might have been the original basis.
The Uto material was made with a sensitizer incorporated into the coating. The coating was black. Exposure to light through an image caused the dyes to bleach imagewise and then the sensitizer was washed out. It was so slow to bleach, it could only be used practically for duplicating images of stained glass windows. The final "stabilized" images still had to be kept in a cool dark place or they would continue to fade.
This is what I have found by a simple search of the internet. I still have to get to Friedman.
PE
This is what I have found by a simple search of the internet. I still have to get to Friedman.
PE
A link to something I found interesting: http://ymdchem.com/en/publics/index/134/
Light selective absorbing dyes.
Not sure how these work, but if it were possible to print tiny dots of different wavelength dyes together then expose...?
Just thinking.
Light selective absorbing dyes.
Not sure how these work, but if it were possible to print tiny dots of different wavelength dyes together then expose...?
Just thinking.
This is basically the way that analog color photography works. Spectral sensitizing dyes are selective as are the image dyes.
Nothing new here.
PE
Nothing new here.
PE
“Dye” is a catch-all label of additives used to accomplish different things in emulsion making. So abandon the traditional laymen connotations of the term. They are called dyes because the earliest examples were used for food and cloth coloring.
Different dyes (think “different chemicals”) accomplish different things.
Spectral sensitizers modify the range of wavelengths which cause a developing speck to form in a silver halide crystal. These additives are what modifies the response to make orthochromatic or panchromatic films, among others. Basic emulsion responds only to UV and blue (strictly speaking, excited only by the energy of those wavelengths). Spectral sensitizing dyes transfer energy from other wavelengths into the silver halide grain to form the developing speck. This category is not strictly limited to sensitizing dye (I’m thinking of KI here), but sensitizing dyes are most commonly used for this and are added during the emulsion making process. So black and white panchromatic film (for example) has these types of dyes in the emulsion. In color film, different dyes are added to the emulsions which are then laid down separately to form the three different layers that are sensitive to different parts of the visible spectrum (i.e. blue, green, red).
The dyes which form the “color” in color film are formed in situ by the reaction between the developer oxidized by development of the silver grain and the dye coupler added to the emulsion for that purpose. These newly formed dyes remain after the silver is dissolved away during bleaching.
Different dyes (think “different chemicals”) accomplish different things.
Spectral sensitizers modify the range of wavelengths which cause a developing speck to form in a silver halide crystal. These additives are what modifies the response to make orthochromatic or panchromatic films, among others. Basic emulsion responds only to UV and blue (strictly speaking, excited only by the energy of those wavelengths). Spectral sensitizing dyes transfer energy from other wavelengths into the silver halide grain to form the developing speck. This category is not strictly limited to sensitizing dye (I’m thinking of KI here), but sensitizing dyes are most commonly used for this and are added during the emulsion making process. So black and white panchromatic film (for example) has these types of dyes in the emulsion. In color film, different dyes are added to the emulsions which are then laid down separately to form the three different layers that are sensitive to different parts of the visible spectrum (i.e. blue, green, red).
The dyes which form the “color” in color film are formed in situ by the reaction between the developer oxidized by development of the silver grain and the dye coupler added to the emulsion for that purpose. These newly formed dyes remain after the silver is dissolved away during bleaching.
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Ok thankyou. So the dyes I linked are just sensitizing dyes then? They don't absorb certain wavelengths of light and then in turn change into that specific color? Like from colorless to color? Or from one color into another color?
I like to think in analogies.
A truck is a type of vehicle similar to a spectral sensitizer is a type of dye.
You wouldn’t use a Porsche to tow your boat to the lake similar to how you wouldn’t use those dyes linked above for analog photography even though a Porsche is a really cool car.
Only a relatively small, carefully tested and selected (or designed) subset of dyes are used for specific roles in emulsion making.
Like any other technical “thing”, the name or label isn’t as important as what are the actual properties of the “thing” and what it needs to do. The label simply acts as shorthand for communicating the properties to others familiar with the context.
In other words, abandon your traditional understanding of the labels and rewire your thoughts to understand what they mean in this specific context (which is what you’re doing, so keep at it...just takes research and practical experience).
Look through the reference materials on thelightfarm.com Denise has collected a rich supply of reference material there
A truck is a type of vehicle similar to a spectral sensitizer is a type of dye.
You wouldn’t use a Porsche to tow your boat to the lake similar to how you wouldn’t use those dyes linked above for analog photography even though a Porsche is a really cool car.
Only a relatively small, carefully tested and selected (or designed) subset of dyes are used for specific roles in emulsion making.
Like any other technical “thing”, the name or label isn’t as important as what are the actual properties of the “thing” and what it needs to do. The label simply acts as shorthand for communicating the properties to others familiar with the context.
In other words, abandon your traditional understanding of the labels and rewire your thoughts to understand what they mean in this specific context (which is what you’re doing, so keep at it...just takes research and practical experience).
Look through the reference materials on thelightfarm.com Denise has collected a rich supply of reference material there
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