BKF-2 Rapid Acid Fixer — reagent kit for 1 litre

Description

BKF-2 is a rapid acid fixer for black-and-white film and paper. A kit of dry reagents from which you mix exactly one litre of working solution.

The fixer is used for accelerated fixing, primarily on specialist technical stock — aerial and X-ray film. It works just as well on ordinary 35 mm and medium-format film. The ammonium chloride in the formula speeds things up: fixing takes 5–7 minutes at 20 °C instead of the usual 10–15.

What is in the kit

Three sachets of reagents for one litre: sodium thiosulphate crystalline — 250 g (large sachet), ammonium chloride — 50 g (medium sachet), sodium metabisulphite — 17 g (small sachet).

How to mix it

1. Pour about 700 ml of hot water (60–70 °C) into a one-litre vessel and dissolve the contents of the large sachet (250 g sodium thiosulphate).

2. Once the salt has fully dissolved and the solution has cleared, add the small sachet (17 g sodium metabisulphite) and dissolve completely.

3. Add the medium sachet (50 g ammonium chloride), dissolve it and let the solution cool to room temperature.

4. Top the solution up to one litre and filter it if necessary.

Use and storage

Fix film for 5–7 minutes at 20 °C. Keep the mixed solution in a tightly closed bottle, in a dark, cool place.

The full formula, the history behind it and a glossary of terms are in our recipe handbook, on the BKF-2 Rapid Acid Fixer page.