Erythrosine

[wildbillbugman]

Hi PE,
Back when I took your Workshop, you introduced us to erythrosine as a green sensitizer. The dye needs to be added prior to precipitation. I wonder if this dye can ever be added after precipitation. My own experiments indicate that it cannot. Thanks
Bill

[dwross]

Hi Bill,

T.Thorne Baker has a recipe in "Photographic Emulsion Technique", 1st edition, p.108, where he adds erythrosin to converted silver immediately before precipitation. I haven't gotten around to trying that recipe yet, but I always trust Baker. That said, I add half my erythrosin 2/3 of the way through digestion, and the other half as a final. No particular reason. That's just the way two dozen variations of trial and error blazed the path to my final, favorite ortho recipe. My guess is that you can add erythrosin just about anywhere in the process. (Caveat: remember, all recommendations here are for gelatin emulsions. All bets are off with synthetic carriers.)

d

[wildbillbugman]

Thank you denise,
I am attempting to use relatively cheap dyes for my emulsions. Sands dyes work well. But $600/g + Convenience fees is just too much.
I have tried adding erythrosine as a finishing component and have newver seen an increase in greensensitivety. I shall atempt it again with your method. But my best emulsions are weird enough to produce totaly different results. 'Cors , I can always return to extracting dye from dead red beetles -
Bill

[desertrat]

It was common practice in the early 20th century for users to sensitize plates after they were purchased. "Photographic Facts and Formulas" by E.J. Wall, 1924, has instructions for this. He has a recipe for Erythrosin, and recommends using the plates within a few days after treating them. If you don't already have the book, it can be downloaded as a .pdf from the internet.

Don't know if you're interested in dunking the finished plates in a dye bath, but just thought I'd mention it as an option.

[wildbillbugman]

Thanks desertrat, In fact I frequently do a quick evaluation of a new dye by soaking the dried plate in a dye solution with a drop of weting agent. What I am hearing is that erythrosine can be added after precipitation. But with my emulsions that is not the case.

[Photo Engineer]

Ok, Erythrosine can be added after pptn. to AgCl emulsions. If added to AgBr or AgBrI emulsions, the full effect is only seen if it is added before pptn. If added after the potn. is complete, then you get 1/2 or less of the full effect.

This is shown in Mees along with comparisons with other dyes.

Also, if you add too much after pptn. you can lose the inherent blue speed of the emulsion. This does not happen if you add it before pptn, as the excess washes out. You essentially get the right amount all the time if added beforehand.

PE

[Kirk Keyes]

PE - so it sounds like it is binding with the AgBr or AgBrI crystals, in both cases, but with the after addition it's just absorbing too much light since it's not washed out to work well?

[Photo Engineer]

Well, it does wash out "properly" if you add it before pptn takes place. And the amount that washes out appears to leave just the right amount behind. It probably does form a salt with Ag+, but I have no proof of that. Just that it works better. Added after pptn, there is only the crystal surface to bond on. In most cases, modern dyes have a positive charge.

PE

[wildbillbugman]

Thanks PE,
My observation has been that, when added after ripening, the erythrosine does little, if anything to increase green sensitivity. But I do not use gelatin, so all bets are off. My emulsions do some things that I have never read about here or elseware. I will report some of these soon, I hope.
Bill

[Hexavalent]

Ok, Erythrosine can be added after pptn. to AgCl emulsions. If added to AgBr or AgBrI emulsions, the full effect is only seen if it is added before pptn. If added after the potn. is complete, then you get 1/2 or less of the full effect.

This is shown in Mees along with comparisons with other dyes.
...

PE

Is this the case with the Sands' dyes (can't recall the exact #'s at the moment) or is it specific to Erythrosine? i.e. if I wanted to add a bit of green sensitizer (Sands) to a AgCl emulsion.