I have found some old colour slides but they have what look like burst blisters all over them.
Was your father a keen amaateur photographer?
Yes, he processed his own.
And therein lies the problem. The slides were Ferraniacolor, an old reversal colour film that was extremely popular in the 1950s. Processing kits made by Johnsons of Hendon were sold that enabled the production of very good slides on the day of taking. That was a great advantage compared to Kodachrome or Ilford Colour which had to be sent away in the post to a central processor. But there was a problem. The kit worked fine in hard-water areas. Included in the instructions, however, was the statement that in soft-water areas, an additional step should be included: a 2% magnesium sulphate solution bath after the colour development stage. There was no definition of what was considered to be soft water and no magnesium sulphate (epsom salts) was provided. Therefore, our and am sure many first efforts at processing Ferraniacolor ended in tears, for the emulsion blistered and burst in places. Once we realised that the water was not hard enough, epsom salts came out of the cupboard (most houses had a packet as a laxative) and the problem disappeared. Since the additional magnesium sulphate bath made no difference in hard water areas, since the stuff is cheap and since the bath was for only a short time, I could never see why Johnsons did not include it in their kit and standard processing instructions. I am sure they lost many customers disappointed by their first and perhaps subsequent efforts if they did not realise that their water was not hard enough.
It was especially galling to have this problem when we did not live in an area with what would be described as 'soft' drinking water. Modern maps show it to be moderately hard. Nothing like London tap water or the water from artesian wells in Cambridgeshire but nevertheless on the hard side.
We threw away most of the blistered Ferraniacolor transparencies many years ago, keeping only a couple that could not be replaced. Below is the detail from one showing the blistering:
Incidentally, the popularity of processing Ferraniacolor was such that manufacturers began making film transparent processing spirals. The film was left on the spiral when it was exposed to light as part of the reversal process. Photoflood lamps (later ordinary 100 watt light bulbs) were used for the exposure with the film spiral held and turned over in a bowl of water to prevent the film from overheating. I had a Polly-Max tank made by Johnsons and introduced in 1955.
With hindsight, I wish I had just used Kodachrome for 35 mm slides. The transparencies have stored extremely well and produce good scans. Unfortunately, Agfa CT18 became popular and we have lots of CT18 transparencies. They have also stored well but the grain, as somebody said, is like footballs.
Short processing instructions for Ferraniacolor are shown at:
http://www.brianpritchard.com/Ferrania%20Reversal%20Processing.jpg
