Old process, fixing before developing

[glbeas]

I thought I'd seen most processes or at least read of them. I was reading through and old book I'd obtained, Photographic Facts and Formulas by Wall and Jordan, and ran into a short section describing how to develop film after it has been fixed! This is an old process dating back to the mid 1800s and used a special developer containing either silver nitrate or mercuric bromide. It proceeds by means of physical development where the silver from the developer is deposited on the slight silver image left after fixing. It says it takes several hours to do this so it's not for the impatient darkroom worker.

Don't that make you sit back and scratch your head?

 

[gainer]

Where it don't itch.

 

[PHOTOTONE]

That sounds supiciously like what we would call today "intensification". A common procedure to "salvage" very thin negatives.

 

[gainer]

There is in fact an intensifier based on physical development. I think a recipe for it is in the Darkroom Cookbook. Film to be physically developed must have considerably more than normal exposure in order to produce enough silver nuclei to survive fixation.

In principle, the photolytic silver remaining after fixing serves as a catalyst for the physical developer which must contain a silver compound. In the normal process, the silver compound is in the emulsion as silver halide which has not received the threshold amount of light to reduce it photolytically.

If it seems that I know a lot about it, don't be fooled. You can't work for NASA for 30 years without picking up a lot of tidbits of general knowledge. An Aerospace Engineer is an Anything Engineer, depending on the current requirements. For some reason, I who entered as an Aeronautical Engineer was assigned to design and compute star charts for Mercury Astronauts to use for backup reentry guidance, which I did, and wound up in simulation and human factors studies.

 

[kevs]

Hi glbeas,

This from Sowerby, A.L.M. (ed.) (1961) Dictionary of Photography: A Reference Book for Amateur and Professional Photographers 19th ed. London: Iliffe Books Ltd. pp 226-227:

You should expose sufficiently, fix in plain hypo (sodium thiosulphate) made slightly alkaline, and wash thoroughly. You can then develop any time in daylight as follows:

Mix a stock solution of:

100 cc dist. water;
24 gm ammonium thiocyanate;
4 gm silver nitrate;
24 gm sodium sulphite;
5 gm hypo;
6 drops 10% potassium bromide solution.

For use, mix 6 cc of the above with 54 cc of dist. water and 2 cc of Azol or the following concentrated paraminophenol developer:

Boil 550 cc water briskly and allow to cool. in 150 cc of it, dissolve 30 gm anhydrous sodium sulphite or double that weight of crystals, and stil in 28.5 gm of paraminophenol to form a cream. Then pour in 175 gm pure caustic soda dissolved in 30 cc water. Add cautiously drop by drop a concentrated soln. of potassium metabisulphite or concentrated hydrochloric acid or glacial acetic acid diluted with an equal amount of water. A maximum of 5 cc will be needed.Stir vigourously after each addition. A white precipitate will form; at first this will redissolve on stirring. Continue until the precipitate fails to dissolve. Then add 325 cc cold water, stir and bottle.

Developing takes up to 12 hrs.

Presumably you'd use this undiluted. It seems like a lot of trouble for little practical benefit.

 

[Photo Engineer]

Catalytic color imaging can be carried out the same way. A color film or paper is exposed, then fixed. Then the image is intensified by catalytic development. This is discussed in a series of patents by Bissonette, Bissonette and Mowrey and Mowrey and Wilkes.

I use it to get variable contrast color images.

PE