I've recently (re)developed an interest in wet plate (tintype, ambrotype). I've also read up, some, on gelatin emulsion making and hand coating, specifically that photographer in Oregon who coats her own, not just plates, but film at ISO 25 or higher, orthochromatic, using yellow food coloring as the orthochromatizing dye (some of you can probably already see where this is going).
Collodion processes are well known to be blue-sensitive -- that is, the unmodified halide (bromide and iodide) is sensitive only to blue and UV light, the highest energy photons being required to produce latent image specks that can be developed into image silver. The same is true of unmodified dry plate emulsions, though the opportunity exists for these emulsions to increase sensitivity through ripening (increasing halide grain size) which can't be done with wet plate due to the drying time limits.
For dry plates, however, it's relatively easy to broaden the spectral sensitivity by dying the emulsion -- there are a number of yellow dyes, for instance, that will add green sensitivity, potentially resulting in an orthochromatic spectral curve, and one of these is commonly found in yellow food coloring.
Due to solubility (polar vs. non-polar), I wouldn't expect these water soluble dyes to be viable to directly dye the salted collodion used to coat a plate (bromide and iodide salts are used in the collodion, but they're ionic compounds), but the sensitizing bath is a water solution of silver nitrate; I don't know of any good reason this solution couldn't be dyed and carry a small amount of the dye into the surface of the collodion while sensitizing. Alternatively, there might be aniline-based dyes with the same effects that are soluble in non-polar systems (or I might be incorrect in thinking of ether/ethanol as primarily non-polar -- I get by, but I'm far from being an organic chemist).
Is anyone aware of this being tried? It seems it ought to be a significant expansion of the utility of wet plate to be able to record a scene over a broader range of light colors, lose less speed with time of day, and even be able to use limited filtration for contrast control.
Collodion processes are well known to be blue-sensitive -- that is, the unmodified halide (bromide and iodide) is sensitive only to blue and UV light, the highest energy photons being required to produce latent image specks that can be developed into image silver. The same is true of unmodified dry plate emulsions, though the opportunity exists for these emulsions to increase sensitivity through ripening (increasing halide grain size) which can't be done with wet plate due to the drying time limits.
For dry plates, however, it's relatively easy to broaden the spectral sensitivity by dying the emulsion -- there are a number of yellow dyes, for instance, that will add green sensitivity, potentially resulting in an orthochromatic spectral curve, and one of these is commonly found in yellow food coloring.
Due to solubility (polar vs. non-polar), I wouldn't expect these water soluble dyes to be viable to directly dye the salted collodion used to coat a plate (bromide and iodide salts are used in the collodion, but they're ionic compounds), but the sensitizing bath is a water solution of silver nitrate; I don't know of any good reason this solution couldn't be dyed and carry a small amount of the dye into the surface of the collodion while sensitizing. Alternatively, there might be aniline-based dyes with the same effects that are soluble in non-polar systems (or I might be incorrect in thinking of ether/ethanol as primarily non-polar -- I get by, but I'm far from being an organic chemist).
Is anyone aware of this being tried? It seems it ought to be a significant expansion of the utility of wet plate to be able to record a scene over a broader range of light colors, lose less speed with time of day, and even be able to use limited filtration for contrast control.
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