Dust on a negative is the bane of a film user’s life. The stage of processing when dust settles is the last—drying. All sorts of professional and amateur drying cabinets have been devised, some using warm, filtered air. Some years ago I needed urgently over a weekend a couple of slides. I photographed what I needed and processed the film in my lab. Looking for somewhere relatively dust free to dry the film, I realised that an alternative was lying right in front of me—a large desiccator. After washing, I left the film on the spiral and simply dropped the whole thing in the empty desiccator (with silica gel in the lower compartment), pumped the air out and left it overnight.
Recently I found an article in Amateur Photographer that described the writer’s experience of using the same method and of how extremely effective it was. Arthur R. Madle (AP 9 February 1955) actually went to the lengths of counting the number, size and nature of the particles on the negatives he produced. The main improvement he obtained was using a desiccator connected to a simple water-driven (filter) pump. He concluded:
The crystal clarity of a film or plate dried in this manner is a joy to behold and well worth the extra trouble involved, particularly as time is gained later in the omission of unnecessary spotting. Over 85 per cent of the spots are eliminated by this method.
Arthur Madle used anhydrous calcium chloride as desiccant. That has been superseded by silica gel. Obviously an identical set-up could be used today since all the components are readily available from laboratory suppliers. However, filter pumps are difficult to fit to modern household taps and care has to be taken that water is not sucked back into the desiccator.
There is an alternative: plastic desiccators containing a manual air pump are available. I would be interested to know if anybody has experience of using these for drying films.
These are screenshots from the Fisher Scientific catalogue: