Kodak Film desensitizer

[Mahler_one]

I was reading through an older edition of Horenstein's technical black and white photography book. He discussed developing by inspection, and mentioned the use of Kodak film desensitizer as being useful if one desires to try such developing. Does anyone have knowledge of such a compound, and if so, what the components are? Is the product commercially available? A google search yielded little information of value, but perhaps I simply didn't find a relevant reference.

Thanks.

Ed

 

[keithwms]

There is indeed a product sold by photographer's formulary that reduces or eliminates red/green sensitivity, so that you can then develop with a red safelight. I forget the name.

 

[keithwms]

Ah yes pinacryptol.

 

[Alex Bishop-Thorpe]

I've got an old textbook that mentions something similar, but that it was very expensive. Apparently not in today's world - looks like it'd be fun for experimenting.

The same textbook also mentions hypersensitisation by using mercury gas, but I'm not game to try that.

 

[steven_e007]

I tried it once, I wasn't very impressed.

I got the Pinacryptol in order to mix up one of Geoffrey Crawley's FX series developers, which requires just a tiny amount of pinocryptol.

What to do with all the rest? So, I tried desensitising a film.

I found it seemed to restrain the film speed A LOT and effected the development - so the eventual results were way off. You would need to adjust film speed and developement times to compensate anyway (well, with the film I used, can't remember what it was but probably Fortepan) and the resulting film had a lot of base fog, so either the pinocryptol creates fog or far more likely it didn't desensitise nearly well enough for a relatively fast modern film. Even then, it was only a quick peek - I didn't risk developing with the lights on the whole time.

Bottom line is, what should you see when you squint at an opaque, unfixed film, dripping with developer, in subdued darkroom light?
I had absolutely no idea, so it didn't help much.

I got the impression that it might have been useful for a slow 1950s glass panchromatic process plate - especially if the user had plenty of experience of developing 'ordinary' plates by inspection, but maybe no longer relevent for modern fast films.

I reckon you'd need to ruin a lot of film to learn what to look for before it was of any use, even if you could find a film / developer combination which it didn't cause problems with. Personally I never fely the urge to try it again.

 

[Ian Grant]

Ilford listed DS Green & DS Yellow tablets in their 1960 Formulae & Packed Chemicals Publication & price list. 3s 3d for 10 Pinacryptol Yellow tablets and 1s 6d for 10 Pynacryptol Green.

However they note that some modern High-Speed films don't respond well to either, and that they can affect the film speed and/or contrast.

I have a few glass phials of Pinacrytol Yellow that would make a few litres of 1:20000 solution, but I think if I wanted to develop by inspection I'd buy some night vision goggles, far more effective and less problematic.

Ian

 

[CBG]

The best info on developing by inspection - DBI - I've seen is at: www.michaelandpaula.com/mp/devinsp.html

The article states DBI isn't intuitive and that one does have to learn what to look for. I'm not sure that DBI is at all limited to 50s style films, although I believe Kodak warns that their T-Max films are not compatible with desensitizers.

 

[David A. Goldfarb]

Karsh famously relied on this heavily, and when Kodak stopped making it due I think to environmental or workplace safety restrictions, they had a case made up in Switzerland specially for him. My impression is that it was to be added to the developer shortly before turning on the green safelight, after most of the development was completed.

 

[Ian Grant]

M.A.S. was talking about an old style film/emulsion in the article. Both Ilford & Kodak no longer recommend the technique, and both issued warnings about possible problems with faster emulsions in the past, the desensitisers dyes will probably react adversely with the dyes incorporated in many modern films, particulalry T-grain emulsions.

Ian

 

[Ian Grant]

Ilford state DS (Pinacryptol) Yellow should only be used as a "Pre Bath", however DS (Pinacryptol) Green can be used as a "Pre Bath" or added to working strength developer as long as it contains less than 1g per litre Hydroquinone. Both have an effect on the development time which needs increasing, and DS Green helps prevent aerial fogging, so will affect contrast too.

Ian

 

[neelin]

from: Photographic Facts and Formulas, E.J. Wall & Franklin I. Jordan (orig. 1924) revised & rewritten by John S. Carroll 1976. ISBN:0-8174-0580-1 (Amphoto) p141

"Another approach to desensitization is to convert the silver bromides in the emulsion to iodide, which is much less sensitive to light, and allows developement of the image in bright light. This was first noted by R. Freund in 1908, and followed by extensive investigation by F.F. Renwick in 1920. If an exposed emulsion is bathed for several minutes in the following bath

Potassium Iodide 10.0g
Sodium Sulphite (dessicated) 10.0g
Potassium thiocyanate 30.0g
water to make 1.0l

it could be developed even in full sunlight, using amidol (diaminophenol) developer freshly commpounded with sodium carbonate. There is some question if this will work with modern, high speed, dye-sensitized emulsions"


I wonder if the last sentence was written by Carroll in 1976 or Wall-Jordan in 1924

robert

 

[Ian Grant]

Frank Renwick was of course a Research Chemist at Ilford, in Essex, at that time, which is prior to his stint at Dupont in the US, he later returned to Ilford as Head of Research. The comments will be John Carroll's.

Ian

 

[Mahler_one]

Thanks to everyone who is commenting. I went to M and P site....one of the options is to use IR devices which evidently make the entire process of DBI very easy. I also found a copy of Steve Anchell's great reference book, the Darkroom Cookbook. He mentions one desensitizer that is still available, i.e., De-tec made by Antec ( www.kyantec.com )....and yes, the product is still available. Mr. Anchell points out that pyro developers will desensitize the film, but one has to judge the highlight densities differently. I'm not sure that I will attempt DBI...sounds a bit intimidating. However, I can see where being able to be a bit "liberated" from time and temperature would be interesting.

 

[Ian Grant]

Interesting comments about D-Tec working less well with D76, D23 etc presumably Xtol too, and potentially causing fogging with Pyro developers.

Since M.A.S. wrote that article the cost of IR devices has dropped significantly, and they are a lot much more readily available,

Ian

 

[Jim Noel]

I regularly develop by inspection. At this moment I have ten students developing lith film to long scale under s red safelight. The next step is to teach them to develop FP4+ utilizing a green safelight for a few seconds at a time after the film is 65-75% developed according to time/tempeerature charts. The secret is knowing what the film should look like for a particular DR. This takes practice.

 

[Mahler_one]

How interesting Jim! Where are you teaching such skills, and why did you decide to teach DBI? Other than M and P, I wasn't aware of anyone who is actually teaching DBI.

Ed