erythrosin & eosin

[JOSarff]

erythrosin CAS 16423-68-0
eosin Y CAS 17372-87-1

would these be correct as sensitizing dyes for a basic emulsion formula?

Thanks a lot.

Joe

[Photo Engineer]

Joe;

Erythrosine is the better known of the two for having activity as a sensitizing dye for emulsions. The wedge spectrograms of Green sensitive Azo type paper was done with Erythrosine. It is a common food coloring and is an active ingredient in Merthiolate. It is easily purchased at a rather low price. My last batch came fro www.kyantec.com

PE

[Marco B]

Joe;

Erythrosine is the better known of the two for having activity as a sensitizing dye for emulsions. The wedge spectrograms of Green sensitive Azo type paper was done with Erythrosine. It is a common food coloring and is an active ingredient in Merthiolate. It is easily purchased at a rather low price. My last batch came fro www.kyantec.com

PE

Interesting, I know these substances as colouring dyes for microscopy. I never realized they had a function as sensitizing dyes. I love these parallels.

[winger]

Interesting, I know these substances as colouring dyes for microscopy. I never realized they had a function as sensitizing dyes. I love these parallels.

Same here!

[Photo Engineer]

What is not as well known, is that in spite of the many publications of the Agfa paper formulas such as Brovira is the fact that Brovira used Erythrosine. The reason it is missed is that the dye was applied, along with about a half dozen other "missed" ingredients, in an overcoat. Thus, Brovira was Ortho-sensitive.

PE

[Photo Engineer]

So much for relying on memory.

After searching several sources I find that Agfa used a green sensitizer for several of its paper products. Some used Erythrosine and some used a dye which as I reported before is unknown (hier ist unbekannt) and they also used a method of applying the dye(s) either in overcoats or added to the emulsion just before coating. It is not clear regarding this either. In any event, at least two dyes were used in Agfa papers and up to two methods were used to incorporate them.

Sorry for the lack of clarity in the last post. I was working from memory. Now I have notes, such as they are.

PE

[hrst]

Did I understand you correctly, are you referring that some sensitizing dyes were added in overcoats? Is it possible that they work there as sensitizers? AFAIK the dye must adhere to the silver halide to pump energy in it in order to work. Is this possible from overcoat?

Thanks.

[Photo Engineer]

There is some indication that dyes were added in overcoats.

It is known that early dyed coatings were coated first and then dipped into a solution of the dye. The emulsion was sensitized by this dip/soak treatment, so why would an overcoat not work?

The German wording is unclear. They use a word which my dictionary translates as "basting sauce" or "gravy". This could mean something coated over the emulsion or something added to the emulsion.

PE

[Ray Rogers]

I have positivly tracked down one of those "unknowns".
I do not think erythrosine was the other.
It seems to me it is possible you might actually be looking at a different formula than what you think
as I don't recall any such wording.... but I will have another quick look.

e-mail me if you want to compare notes or describe that "indication".

OK,
I had a quick look and I see where you are getting that erythrosine bit...
It still seems you might be mixing two different formulas.

Ray

[Ray Rogers]

Is it possible that they work there as sensitizers? AFAIK the dye must adhere to the silver halide to pump energy in it in order to work. Is this possible from overcoat?

You are correct.
Generally speaking, dyes do need to be in close contact with the AgX, however there are some rather interseting ideas or theories on what might be possible under special conditions, although in the "dip" method, there was enough time allowed for the dyes to be fully absorbed/adsorbed... so no fancy theories are needed.

I guess it is possible that some coating methods would not allow for such absorption to occur and so the desired sensitization might not take effect.
at least not immeadiately.

However, OTOH, it is well known that many chemicals can be either
mixed into the emulsion
or
coated as a separate layer and still be of some utility.

Sometimes the chemicals can even be added to the developer or the packaging.