Thanks for figuring that borax weight per gallon value for me. I think I'll probably try figuring it out on my own to see if I can match your number. Sort of an intellectual challenge, since I took college chemstry so long ago. However, I did help my daughter with her chemistry when she was in high school a few years ago.

I should have said that my balance has a resolution of 0.1 g, or maybe 0.05 g, so that I should be able to measure in the range of 1 g reasonably well. With that in mind I weighed out 1.65-1.70 g of borax and added it to a gallon of H2O. After agitation I tested it, and to my surprise got a purple brown color that matches nothing on my AquaChek bottle. I'm guessing it's probably close to what the 15 ppm color sample should be, but maybe my strip are NG? The bottle says 2008/04 on the bottom, so they should be fresh. After several hours I agitated the solution and tested it again with the same results.

Hmmm, now I really perplexed. I think I may try getting another bottle of test strips from a different supplier. I think I also saw another brand of borate test strips at a web site somewhere.

Al