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Discussion in 'Silver Gelatin Based Emulsion Making & Coating' started by narigas2006, Jan 31, 2007.
what can I add to my emulsion to make it sensitive to yellow? Many thanks.
Richard, that would not be an ortho dye, it would end up making a pan sensitive film.
I have no idea where to get such a dye. It would be blue in color. I have been unable to get one.
An ortho dye is magenta in color. The least expensive would be Erythrosine, but it depends on how you want to use it and the emulsion type.
Would it change the film sensitivity?
Would the Erythrosine give any change to sensitivity? Also, thyocianate without the gold salts, would it cause increase sensitivity? Many thanks.
Erythrosine adds sensitivity to green light.
I would use sodium thiosulfate instead of thiocyanate. This will cause an increase in about 2 contrast grades and up to 3 or 4 stops in speed, but the time and temperature must be determined for each emulsion.
Thanks heaps! Other thing, I found out that Eosin was also added to emulsions to change their sensitivity. I have yellowish eosin that is used in microscopy, could I use that? Also, I have some ripened emulsion frozen (uncoated), could I mix both of eosin and the tiosulfate to it now? It's also washed. Many thanks again!
Eosin, being yellow, is a sensitizer to blue light and is a weak sensitizer IIRC.
It will add no really noticable difference to the speed of the emulsion, nor any significant change to the spectral sensitivity, as the emulsion is already blue sensitive.
The sequence is outlined in another post in more detail, but basically you add the hypo, with or without gold, hold at a predetermined temperature for a predetermined time. I am using 1 hour at 60 degrees C. for my emulsions, but that may vary.
After this, you add the dye at 40 deg C and hold for 15 minutes. That is the usual sequence.
However, if it is premade by a manufacturer, there may already be dye on the emulsion, or it may have restrainers in it to prevent the action of the addition of hypo. If it is already treated with hypo, further treatment will fog it, in all probability.
I have posted elsewhere, that freezing an emulsion will ruin it in most all cases. It disrupts the action of the gelatin by denaturing it and will often cause very bad results.
I've read about Pinacyanol Chloride being used to sensitize emulsions in some cases. What color does this sensitize them to?
Without having a spectrogram of the dye, and I can't remember the color, all I can say is that it would sensitize in the region opposite to its color.
This is a general rule, so a yellow dye is a blue sensitizer and a magenta dye is a green sensitizer, and a cyan dye is a red sensitizer. This rules out "J" aggregates which shift sensitization by about 100 nanometers to longer wavelengths. So with "J" aggregates, a magenta dye would be a red sensitizer. It will turn cyan when added to the emulsion by aggregating.
Ah. Then, could it be used in combination with erythrosine to achieve panchromatic sensitivity?
Probably yes. Not having done the experiment, I have no idea.
You would have to make 2 sensitized emulsions, 1 green and 1 red for this to work properly though.
Interesting, PE. Would they them be mixed and coated, or coated atop one another?
Either way could be used, but for quality sake I suggest that they be mixed 1:1 and coated in 1 layer for a start. However, proper testing would require a spectrosensitometer or a very special step wedge sensitive to a variety of colors. I have such a design, but it is rather messy to build and calibrate. I do have a spectrosensitometer available to me though, so if I can help....
This summer I plan to start really experimenting with emulsion making. My eventual goal is to get something that can be useful for my autochrome project.
The one thing that's been keeping me from really starting experiments is the cost of silver nitrate; but if I can get up $200 or so to buy a pound of it, I have a feeling that that'll last me awhile.
I've been looking around for a list of prices and sources of things. Where's a good place to find erythrosine?
They have it but it is unlisted. It is about $20 / gram.
Good to know. And from their site, they seem to be willing to sell to anyone. Do you know offhand if they have other dyes as well?
AFAIK, they do not. Kodak listed about 20 dyes in their Eastman Chemicals catalog at one time but they are discontinued. Other sources are drying up and the dyes I have are not very good. Broad, form "J" type aggregates and etc....
Probably the best idea to start simply though. If only silver nitrate wasn't so damn expensive.
Somebody should see if there are enough people to go in on a bulk purchase of silver nitrate. From B&H, it only ends up being like 66 cents / gram if you buy a pound, and I bet it could be had for cheaper elsewhere. In smaller amounts its like 2 or 3 times that ...