F-6a is an odorless fixer that eliminates the boric acid of the F-5 formula, and uses Kodalk (Sodium Metaborate) instead. Ansel Adams modified the formula by using one-half the hardener (potassium alum) given in the original F-6 formula. This facilitates toning and washing of the prints, as well as spotting, and causes no adverse affects provided the solution and drying temperatures are not excessively warm. The ingredients must be mixed in the order given.
WORKING SOLUTION
| Chemical | Amount | Units |
|---|---|---|
| Water (125°F/52°C) | 600 | ml |
| Sodium thiosulfate (hypo) | 240 | g |
| Sodium sulfite (dessic) | 15 | g |
| Acetic acid (28%) | 48 | ml |
| Sodium metaborate | 15 | g |
| Potassium alum | 15 | g |
| Cold water to make | 1000 | ml |
REFERENCE
The Print, Ansel Adams, p.193.
Fixer 6a (Adams Version),
The Darkroom Cookbook,
Stephen G. Anchell, p.153.