Gold sensitization of photographic emulsion

Ian,
Not when you are working on a True Passion !
Bill

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Originally Posted by wildbillbugman

But I do know that, when residual dye solution is left to dry on an eyedropper or beaker, it turns bright gold in color.

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I've been wondering about this as well - pinacyanol shows the same behavior. I assume this is some broadband fluorescence effect but have no idea why this occurs on dried layers.

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Originally Posted by Hologram

I've been wondering about this as well - pinacyanol shows the same behavior. I assume this is some broadband fluorescence effect but have no idea why this occurs on dried layers.

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If I may ask, how do you use the pinacyanol? I've had a bottle (chloride) on my desk for a couple of months, taunting me -- just daring me to put it in something. I've got a couple of ideas, but if you've been there already, I'd love piggyback off your experience before I jump down the rabbit hole. Apologies if you've talked about this before.

d

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Originally Posted by dwross

If I may ask, how do you use the pinacyanol?

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Denise, I've used pinacyanol for photopolymers and AgX emulsions. With regards to AgX, most of my attempts related to Jeff Blyth's diffusion method. That's to say, I hardly did any sulfur/gold sensitization. Instead, I heavily relied on ascorbate reduction sensitization. I don't know what the situation looks like for more sophisticated photographic emulsions, but with crude red-sensitive holographic emulsions the combination of pinacyanol and ascorbate resulted in surprisingly good photo speed.

To come back to gold sensitization) Wolfgang Baier, Die Geschichte der Fotografie, mentions the work of Dr. F. Kropff, who was said to have done research on gold sensitization for Gevaert in the mid 1920s...

Thanks much for the info. It's a little brighter down that rabbit hole. I doubt your emulsions are any more 'crude' than mine. I'm going to try to push my favorite emulsion's sensitivity up a notch. I got spoiled by summer emulsion speeds.
d

Sands does not reveal the chemical structure of its dyes. No dye that I know of contains gold. Some special dyes are complexed with Osmium.

PE

PE, what would be an example of 1 or 2 gold compounds that would work with S+Au sensitization? Just curious to see how expensive this stuff is.

KAuCl4 is commonly used.

It is used at 1/3 with sulfur.

PE

Thanks Ron. And since I've got you... what's a typical Iridium compound that's used to affect LIK (latent image keeping) & reciprocity characteristics? Just curious; can you tell I'm reading your book?

Iridium is noted in the extensive Appendix telling you how to prepare the solution for use. It is not a simple matter of using Iridium Chloride. You must prepare the proper solution or it goes bad.

Also, note that the point of addition in the make is critical. That is mentioned in the book but T&E is the only way to find the optimum place. It is usually added during the growth phase.

PE