Disregard the streaks of colour that may develop at edge of test strip. Use a freshly prepared set of standard papers with each series of samples tested. 3 BO 3 is present the paper will change to yellowish-red. If negative, the paper will change to yellow. Compare the colour between the standards and the sample, taking into account the dilution of the samples, if any.
Similar colour is related to similar boric acid content.
The procedure is semi-quantitative. It will give a reasonable estimation of the boric acid or borates content. On long storage, borate is leached from glassware. 11, method no. 12, method no.