I have successfully used the same bottle of powder for 2 years, but I keep it in a cool, dark, dry cabinet. It still turned progressively darker shades of gray, but still was good (and accurate) even when it got pretty dark. I recently had to buy a new container. Ordered it at this site, arrived in about 3 days. The number on the container in Ben's kit is the Taylor number, so they're the same.


http://www.spspools-spas.com/

Janet