old PH test strips

We have found that the four and five way test strips for testing pool water quality do not give consistent readings the next summer, even though we keep them tightly sealed and in the dark.

I believe that some of the "indicator" chemicals break down over time.

Litmus paper is actually paper treated with an infusion of organics from certain lichens, and like any other biological substance, these can age and degrade. Chemicals in the air- ie chlorine concentrations around the pool chemicals where the bottle is opened closed and stored- also could be accelerating the downgrade of our test strips.

Test strips and papers are inexpensive, but I would describe them as "qualitative/semi quantitative." They are a blunt instrument. PH or alkalinity meters are available and relatively inexpensive and give far more precise information about the solution than the attribute data of a color change indicator. ANd operator interpretation is less of an issue than color perception differences under different lighting conditions/ operators etc.

milo

Thank you.

My knowledge base is of electronics and mechanics, so my query may have appeared as overly simplistic. I appreciate someone taking the time.

A meter. Where's the smacking head emodicon?

Thanks again.

you're welcome. I found this one on flikr:

milo