How To Tell When The Chemicals Are Exhausted

Making sure that all of the chemicals in the tray are fresh is your responsibility. Your instructor will provide you with instructions for mixing the tray solutions from the stock solutions on the shelves (or see above for a review of this). We encourage you not to waste chemicals by dumping the trays of chemistry unless they are exhausted, so you can help to conserve chemistry (and the environment) by learning the tell-tale signs of when chemistry is beyond its useful life.

Developer: Fresh developer has an amber of light brown color when fresh. When exhausted, it will turn dark brown and you may also notice a soot-like precipitate in the bottom of the tray. Generally, developers will oxidize overnight, so this chemical should be mixed fresh every morning.

Stop Bath: Stop bath should be changed whenever the developer is changed. Fresh stop bath feels slippery to the fingers. Exhausted stop bath feels slimy. If you every take a print out of the lab for viewing after it is fixed and notice that it has pink or blue stains, chances are that the stop bath is exhausted.

Fixer: Fixer is a relatively costly chemical and should not be dumped unless it tests bad with Hypo-Chek, a test chemical in small dropper bottles that is located on the shelf in the lab. Your instructor will show you how to use it. When a drop of this chemical is placed in a tray of exhausted fixer, it produces a thick milky-white precipitate that does not disappear immediately when the tray is shaken. Exhausted fixer should never be poured down the drain, but rather into the silver-recovery pails in the group darkroom.

Hypo-Clear: A gallon of hypo-clear will treat approximately fifty 8"x10" prints. After that amount has been put through it, it should be discarded.