Surface developer vs. depth developer

[dpurdy]

It's been years since I researched Beutlers but I believe it was more relevant in the older days when films had thicker emulsions. Crawley designed this developer to process only the surface of the emulsion for greater sharpness. Originally the formula called for a tiny amount of Potassium Iodide, which I still have, but modern films don't need any of this. I am standardized on it for 8x10 Fp4 and I don't bother with the iodide. I also agitate like a normal film though Beutlers calls for less. I can build plenty of density to print platinum without restrainer for contrast.

 

[Andrew O'Neill]

It's been years since I researched Beutlers but I believe it was more relevant in the older days when films had thicker emulsions. Crawley designed this developer to process only the surface of the emulsion for greater sharpness. Originally the formula called for a tiny amount of Potassium Iodide, which I still have, but modern films don't need any of this. I am standardized on it for 8x10 Fp4 and I don't bother with the iodide. I also agitate like a normal film though Beutlers calls for less. I can build plenty of density to print platinum without restrainer for contrast.

I thought Beutlers was designed by Willi Beutler? I've never used it with Potassium Iodide. I'll have to dig up my notes from the 90's...

 

[dpurdy]

I thought Beutlers was designed by Willi Beutler? I've never used it with Potassium Iodide. I'll have to dig up my notes from the 90's...

I always thought it was a Crawley formula but it is not the first time I have been wrong. I think the theory is the same. With thicker emulsion light scatters within the depth of emulsion and causes less sharpness. Butler's is supposed to remedy that.

 

[Milpool]

I'm just wondering how relevant the term "depth/surface" developer is today, with thin emulsion films. Quite honestly, I've never heard of this term until very recently. And what is the example of a "surface" developer? Are these types compensating developers? Any developer that is diluted? Semi-stand? Crawley's Acuspecial?

In the old, old days it had more relevance and also meant a variety of things. In the context of more modern materials/emulsions it seems to have been narrowed mostly to solvent effects. For example, the late Ron Mowrey, who worked at Kodak for many years, gave an example of an emulsion testing developer used internally at Kodak which he referred to as a surface developer (ie no solvent action/access to buried latent image sites):

g/l
Metol: 2.5
Ascorbic acid: 10.0
Sodium metaborate: 35.0
KBr: 0.4
Target pH 9.8

 

[relistan]

I'm just wondering how relevant the term "depth/surface" developer is today, with thin emulsion films. Quite honestly, I've never heard of this term until very recently. And what is the example of a "surface" developer? Are these types compensating developers? Any developer that is diluted? Semi-stand? Crawley's Acuspecial?

My understanding, from all my previous reading, is that we’re talking about whether the developer has the ability to reach latent image centers that are not at the surface of the emulsion. Even a thin emulsion has latent image centers that are exposed but not directly reachable without some solvent effect, because they are behind/under non exposed halides. Not being able to reach those latent image centers is one reason why non solvent developers often have trouble reaching box speed. The positive effect of only developing surface halides is perceived sharpness. The negative is less overlap of grain, leading to perceived graininess, and potentially lower box speed.

I am not sure without solvency how one would make a non-surface developer. Perhaps there are other ways.

Solvent developers have a second characteristic, mentioned above, which is that the dissolved silver halides can be redeposited onto the emulsion. This can lead to a further reduction in perceived graininess.

A “depth” developer would presumably then be a developer that is, either through solvency, or some other means, able to reach latent image centers deeper in the emulsion. This may or may not redeposit silver. Even some solvent developers contain silver chelating agents to help prevent that.

I’m sure Alan or Rudeofus can correct whatever I’ve gotten wrong there.

 

[Andrew O'Neill]

Very well explained, @relistan. Really good info. Thank you.