The DARKROOM COOKBOOK, Third Edition

272 THE DARKROOM COOKBOOK
FILM: Film should be clear in 5 minutes and fully fi xed in 10. Discard when the clearing time
is close to 10 minutes. The hardener can be mixed separately as a stock solution (see the following
formula).
PAPER: Use the two-bath method, 5 minutes in each bath. Do not use hardener in this fi xer if
you intend to tone the print.
FORMULA #130
Kodak F-5a
Hardener
Water at 125F/52C, 500.0 ml
Sodium sulfi te, 75.0 g
Acetic acid, 28% solution, 235.0 ml
Boric acid, crystals, 37.5 g
Potassium alum, dodecahydrate, 75.0 g
Water to make 1.0 liter
The sodium sulfi te should be dissolved completely before adding the acetic acid. After the
sulfi te-acid solution has been mixed thoroughly, add the potassium alum with constant stirring.
To make an acid-hardening fi xing bath add 250.0 ml of hardener to 1.0 liter of cool hypo
solution. If the hypo is not thoroughly dissolved before adding the hardener, a precipitate of
sulfur is likely to form.
To make a pre-hardening bath dilute 250.0 ml of the stock hardener solution in 1.0 liter
of water. Harden fi lm or paper for 1 minute prior to fi xing.
FORMULA #131
Kodak F-6
Odorless Acid-Hardening Fixer
Most fi xers have strong odors caused by sulfur dioxide. The substitution of balanced alkali for
boric acid in the F-6 formula eliminates the odor almost entirely.
Water at 125F/52C, 600.0 ml
Sodium thiosulfate, 240.0 g
Sodium sulfi te, 15.0 g
Acetic acid, 28% solution, 48.0 ml
*Balanced alkali, 15.0 g
Potassium alum, 15.0 g
Water to make 1.0 liter
* Sodium metaborate may be used as a substitute.
To prevent sulfurization mix the alum separately in a small amount of hot water. Add this
solution last with rapid stirring.