Rollei RCS Citrin is a citric acid stop bath, 1 litre concentrate, for film and paper.
What it is for
A stop bath halts development instantly, which is what makes the development time the one you set rather than the one that happened. Its second job is to extend the fixer's life: without it, alkaline developer is carried straight into the fixer and exhausts it faster.
How to dilute it
The working dilution is від 1+10 до 1+20.
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 wide dilution range makes a litre go a long way. The difference from the cheaper Moersch stop bath is mostly pack size and concentration.
