Tuesday, 25 September 2012

Black and White Film: Reversal Processing

A query from a reader in Amateur Photographer brought back memories of black-and-white reversal processing in the 1950s and 1960s. The reader, who described himself as a technophobe, was asking about the discontinued Agfa Scala and the still-available Fomapan reversal films. Clearly the readers is not a techophobe if he wants to make black-and-white slides or filmstrips by reversal processing but a neophobe. 'Wet' processing is far more technically involved than using a digital camera.

In the Silverprint website, Foma reversal processing kits are available along with the instructions. Also shown is the Ilford Application Sheet from 2003, Reversal Processing Using Ilford Black & White Films to Make Monochrome Transparencies. This Ilford sheet shows the use of potassium permanganate and concentrated sulphuric acid as the bleach bath. Concentrated or even dilute sulphuric acid is not pleasant to have around the house. I remembered that I had reversal processed Ilford FP3 and Pan F to make slides in the 1950s/early 1960s and that I had not used the permanganate-sulphuric acid bleach. I then remembered where I had found an alternative.

Stanley W Bowler's article, Simplified Reversal, in the British Journal Photographic Almanac 1956 (a 1955 Christmas present) states:

Reversal Bath — also known as the Bleach Bath 
The continued insistence in many published formulae on the use of concentrated sulphuric acid is a very real objection, and one to which the writer subscribes fully, having once been burnt by this acid... 
At the suggestion of Mr A.R. Pippard of Johnsons' laboratory, the following alternative bleach bath was tried: 
  Potassium bichromate [now called potassium dichromate]  5gm
  Sodium bisulphate (crystals)                                        25gm
  Water, to make up to                                             1000cc [ml]
This reversal or bleach bath works perfectly satisfactorily and no perceptible difference has been found between it and the formula made up with sulphuric acid. It is essential, however, that fresh clean crystals of the sodium bisulphate are used for the bath to be effective — the fact that this material will not keep indefintely under any but the best of conditions has precluded its being supplied, as one might have expected, as part of a reversal kit of chemicals.
Similarly, a potassium permanganate reversal bath may also be used, using 2 grammes of permanganate and 25 grammes of sodium bisulphate per litre. It should be noted that this bath may be used once only and then discarded.

Why the Ilford Application Sheet does not include this information I do not know.

So, if the fancy takes you to try reversal processing of black-and-white film, like FP4, you can avoid the use of highly corrosive sulphuric acid.

BJP Almanacs are readily available
from Alibris, Abebooks and eBay

The first page of Bowler's article

Silverprint links for reversal processing