Edwal Hypo-Check checks your fixing solution for exhaustion due to silver saturation.

One or two drops are sufficient to test the fixer. If the fixer is still in good condition, the bath is intact.

If a cloudy precipitate forms when Hypo-Check is added, the bath is exhausted and the fixer should be disposed of.

A 3/4-ounce bottle is sufficient for around 800 tests.

Edwal Hypo-Check is an essential specialised chemical for the darkroom, enabling the rapid testing of fixer baths (for film and photographic paper) for exhaustion. The liquid tests whether the fixing bath has become saturated due to an excessively high concentration of dissolved silver and is therefore unusable.

How it works and how to use it

The testing procedure is extremely simple and provides immediate results:

Testing: Simply add 1 to 2 drops of Edwal Hypo Check directly into the used fixing bath (or, to be on the safe side, transfer a small sample of approx. 10–20 ml to a separate glass). [1, 2]

Observe the reaction:

A milky-white cloudiness (precipitate) forms: The fixing bath is saturated with silver, has become exhausted and must be disposed of immediately.

The liquid remains clear: The fixing bath is still active and can be reused without hesitation. The test does not damage the bath. [1, 2]

Why is this important?

An exhausted fixing bath loses its ability to completely dissolve undeveloped silver halide from the emulsion. In the long term, this leads to negatives or prints becoming blotchy, fading or taking on a brownish-yellow tinge, which compromises the archival stability of your images.

A small bottle of approx. 22 ml or 4 oz goes a very long way and is sufficient for 800 tests.