Cadmium in Film Emulsions

braxus · Jan 22, 2023

Going on a new thread here, continuing from another thread. Kodak used Cadmium in some of its film emulsions in the past, including Panatomic X. What other emulsions were known to use Cadmium? Was Verichrome Pan one of them? How easy is it for them to reformulate the emulsion to remove the Cadmium and still get similar results?

Cadmium was a banned substance at one point, which is why they no longer use it in emulsions. What exactly does Cadmium do for the emulsion anyway? Also is it this that helps the film keep longer during storage?

Peter Schrager · Jan 22, 2023

I can't answer your question but I do know that they used gold in Super XX and possibly in Azo Paper.
Since I've been making my own paper emulsions I'm very curious what they used to make AZO last forever?

Sal Santamaura · Jan 22, 2023

Peter Schrager said:
...I'm very curious what they used to make AZO last forever?

I'm not sure its longevity is related to any particular component. Rather, it's likely just a result of the paper's extremely low sensitivity, rendering it resistant to fogging from background radiation.

Peter Schrager · Jan 22, 2023

Sal Santamaura said:
I'm not sure its longevity is related to any particular component. Rather, it's likely just a result of the paper's extremely low sensitivity, rendering it resistant to fogging from background radiation.

what do you mean by low sensitivity?

relistan · Jan 22, 2023

I do not know for sure what they were using it for, but I would guess it was in sensitizing dyes.

Peter Schrager · Jan 22, 2023

relistan said:
I do not know for sure what they were using it for, but I would guess it was in sensitizing dyes.

here's the answer:
Cadmium for contrast control
there are many other substitutes for cadmium
PMT;Rhodium;Copper;Iodide. mostly the chloride
Also Nickel; Cobalt; Calcium all the chloride version

Sirius Glass · Jan 22, 2023

Verichrome Pan had chromium in the emulsion.

MattKing · Jan 22, 2023

Peter Schrager said:
what do you mean by low sensitivity?

It requires a lot of light - most enlargers don't come close to enough. It was designed for contact printing.

MattKing · Jan 22, 2023

Cadmium was something that did the job well at reasonable cost. When its environmental issues caused it to be restricted, the manufacturers who made use of it designed replacements that did the same things.
There really was nothing magical about it.
Its replacement coincided with other changes - improvements that led to higher sensitivity, finer grain, easier manufacturing, all sorts of change. Those changes weren't necessitated by replacing Cadmium, but the need to replace Cadmium influenced the timing of when those other improvements were made.

Andrew O'Neill · Jan 22, 2023

Scroll down to what Donald Q. says about Cadmium...

https://www.photrio.com/forum/threads/panatomic-x-wow.16998/page-2

gone · Jan 22, 2023

If it's in the emulsion then it's safe. It's probably a teeny tiny amount anyway. Artists paints have a lot of it in them, but again, it's encapsulated so no worries, just remember which end of the brush to hold in your mouth. Just kidding, in this form it's not going to hurt you. They've been using this substance since, literally, the Dark Ages. The only dangerous part is in the grinding of the pigments, you don't want to inhale it. Once it's in the paint it's totally safe. It's the solvents that are dangerous, they are absorbed right through your skin,

But many things are like this. When I was painting pottery for Margie Weinstein in Albuquerque, we had to leave the studio when they mixed up the porcelain for our clay. That stuff is murder on your lungs.

braxus · Jan 22, 2023

Donald Qualls said:
Highly probable -- it's my understanding that most commercial emulsions did prior to the 1970s (cadmium is chemically similar to silver, but slightly less reactive, which makes it useful for controlling crystal growth, reaction rates, etc.). Unlike emulsions such as Plus-X and Tri-X that were reformulated without the cadmium at some point, there was little enough market for Pan-X by the time that reformulation was necessary to make it uneconomical to do so -- faster films had gotten enough finer grain that they could replace Pan-X for most applications, and Tech Pan was available as well by that time.

Here was his answer from 2006.

Sal Santamaura · Jan 22, 2023

Peter Schrager said:
what do you mean by low sensitivity?

What Matt said:

MattKing said:
It requires a lot of light - most enlargers don't come close to enough. It was designed for contact printing.

Peter Schrager · Jan 22, 2023

Sal Santamaura said:
I'm not sure its longevity is related to any particular component. Rather, it's likely just a result of the paper's extremely low sensitivity, rendering it resistant to fogging from background radiation.

I make my own POP Paper and it won't last; it also has low sensitivity so there is some magic ingredient that Kodak used to make the AZO last forever..unfortunately Ron Mowrey is gone so the info is lost or in the files at Kodak Park! Adox currently makes AZO grade 3 and even they have no idea how long the shelf life is going to be.
I recently made some Gaslight Paper which is basically an AZO type formula. I have more work to do but it looks promising. I will have to put some in the freezer and take it out in 6 months to see if there is any loss of image...

halfaman · Jan 23, 2023

Peter Schrager said:
I can't answer your question but I do know that they used gold in Super XX and possibly in Azo Paper.
Since I've been making my own paper emulsions I'm very curious what they used to make AZO last forever?

Not only AZO. There is an former Spanish photographic manufacturer called Valca which had an fix grade enlarging paper that after more than 30 years prints perfectly with minimum traces of fog (no production date on the boxes but they went out of business on 1993).

On the other hand, the paper from other old spanish manufacturer called Negra that closed 5-6 years before Valca is badly fogged and unusable. So there is something going on with paper longevity...

relistan · Jan 23, 2023

Looking up patents, it seems there were a number of uses of cadmium or cadmium salts in emulsions. They were used with sensitizing dyes, to control dispersion of others compounds in the emulsion, and as an emulsion stabilizer. Relative to the paper age discussion, I think this 1966 patent is the most relevant:

Cadmium bromide was unexpectedly found to stabilize silver halide emulsions precipitated in the presence of rhodium salts in that it reduces the loss of contrast and speed change upon storage. Cadmium bromide also acts to increase the contrast in a synergistic manner. Other closely related compounds such as potassium bromide and cadmium chloride did not have these properties as will be shown hereinafter.

US3488709A - Stabilizing silver halide emulsions with cadmium bromide - Google Patents

Guillaume Zuili · Jan 24, 2023

MattKing said:
Cadmium was something that did the job well at reasonable cost. When its environmental issues caused it to be restricted, the manufacturers who made use of it designed replacements that did the same things.
There really was nothing magical about it.
Its replacement coincided with other changes - improvements that led to higher sensitivity, finer grain, easier manufacturing, all sorts of change. Those changes weren't necessitated by replacing Cadmium, but the need to replace Cadmium influenced the timing of when those other improvements were made.

I don't know about "nothing magical it".
Portriga Rapid comes to my mind as a "before" and "after" Cadmium.
There was that magical something that was no more.
In Lith for instance all vintage papers with cadmium Lith like a charm. The same later ones behave way differently.

MattKing · Jan 24, 2023

The Cadmium probably didn't itself supply the magic. But the changes that happened may have taken it away.
I doubt that any of the papers that Lithed were designed with that in mind. In fact, I'm sure they weren't .

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