Strengthening Film Emulsion

What I know about it is that the more alkali a dev is, the more the gelatin will soften.
But I'm not sure if if Pyrocat is more alkali than TFX-2.

Never heard that glycin would harden emulsion, but borates (borax, metaborate) used in developers will.

Jorge O

 

Efke, or rather fotoimpex, recommend a hardening fixer.

 

I recently came across a book of Agfa photo chemistry formulas from the thirties - one formula is called a "Chrome Alum Hardening Bath" and it is used in place of a regular stop bath (short stop as Agfa calls it). Its purpose is to give additional hardening to the film, particularly in hot weather or for tropical development.

It's 30 grams of Potassium Chrome-Alum to one liter of water.

Is anyone familiar with this, or have an opinion as to whether it may help with the Efke scratches?
juan

 

Alum is generally considered useful for hardening emulsions. However there are debates about the archival effects.

The subject comes up occasionally in relation to papermaking and watercolor painting. I don't know the answer to the archival question. I've used alum in homemade sizing for my homemade papers but I haven't had these papers nearly long enough to evaluate the archival effects.

 

Interesting. Never heard of a hardening developer before.
Just hardening fixers. Mybe what Francesco is looking for is a hardening fixer.

Jorge O

 

I suspect the scratches occur during the manufacturing of the film, not during the processing.

However I haven't seen any scratches in my Efke R100 (120 rollfilm).

 

The answer to the original question is yes, absolutely. Tanning developers that contain either pyrogallol or pyrocatechin will harden the emulsion of films during processing.

 

..

 

Aggie,

It was not clear to me when the scratching took place, whether with pyrocat or with TFX-2. But regardless, even though pyrocatechin and pyrogallol harden negative emulsions they don't make them scratch proof when still wet.

Sandy

 

Sandy:

I agree with you that the emulsion is at risk when wet, regardless of the developer. When dried that is another story

I had some home developing E6 film and getting scratches in the processing cycle. So did some experiments and found that the film emulsion was much stronger when dry (I mean much stronger).

I believe the final bath which contained formaldehyde was the hardening agent.

- Mike

 

I think it must be a coincidence because as far as I know the glycin in FX-2 would not harden the emulsion more than the pyrocatechin in Pyrocat-HD.

Also, someone mentioned the issue of alkalinity earlier. It is true that a very alkaline developer will result in more gelatin swelling, and this could make the emulsion more susceptible to scratchiong. But both TFX-2 and Pyrocat-HD use potassium carbonate as the accelerator and should work at about the same pH. I don't know this for sure because I have never tested the alkalinity of TFX-2. If you have a way of testing it you can compare to Pyrocat-HD which works at about 10.9.

But I am just curious. How are you managing to scratch the emulsion side of film developing in tubes? In principle nothing should be touching the emulsion side of the film to scratch it. Or are the scratches on the base side? If so, check the tubes because you might have some kind of burr on the lips or inside that is scratching the back of the film when you load and unload it.

 

I have never had problems with scratches with 35mm or 120 roll. But sheet film is a different story. My guess is that I am at fault most of the time and most of my scratches occur when either loading or removing film from the holders.

A few years back I standardized on TMX Readyloads for my field trips. It's an age thing But while I significantly reduced the weight I was carrying, I also had the benefits of no dust spots and 100% scratch free negatives

I still use regular sheet film in all formats and every now and then a negative will get scratched. But interestingly the scratches seem more prevalent with 4x5 film, and my 5x7 and 8x10 seem to escape the problem.

- Mike