Moersch ATS Alkaline is a rapid ammonium thiosulphate fixer, 1 л concentrate, pH 7,5–8,0. Odourless.
What it is for
An alkaline fixer is needed where an ordinary acid one would ruin the work: after pyro and staining developers, acid destroys the very stain the developer was chosen for. It also washes out of baryta paper more easily.
How to dilute it
The working dilution is від 1+5 до 1+10.
A litre of concentrate fixes 150 to 200 films. Fixing time at 1+5: film 2–4 minutes, paper 45–120 seconds.
The solution is replenishable — kept and reused, with development time extended as it exhausts. Keep count of the films put through it; that is the only way to avoid an underdeveloped roll at the end of its life.
Storage
Sealed concentrate keeps well but dislikes air: the emptier the bottle, the faster it oxidises. Decant the remainder into a smaller bottle, or displace the air — that is what gets a concentrate to its last measure.
How it compares
The difference between an alkaline and a slightly acid fixer is not a formality. The alkaline one is required if you develop in staining developers: acid destroys the pyro stain the developer was chosen for.
