Dip the Time Sensitive Peroxide test strip into the solution for 1-2 seconds. Do not swirl.
Remove strip, and hold level. Do not shake off excess water.
Evaluate the color of the test pad beginning at 0 seconds.
If the white pad turns purple, then black within:
2-3 seconds: 10% concentration
10-15 seconds: 5% concentration
30-40 seconds: 3% concentration
60-75 seconds: 2% concentration
Note: Reaction times are adjusted specifically for each batch.
Note: If the solution is for contact lenses, the solution (3%) will remain white for 20 seconds, then turn black.
The Time Sensitive Peroxide test strip can also be used to confirm the strength of 35% food grade peroxide by mixing 1 part 35% peroxide solution with 2.5 parts water to yield a concentration of 10%. If the color change is not immediate, then the initial concentration was not 35% (or a mistake was made in the dilution). Try other dilutions to zero in on the actual strength, e.g. 1:6 should give you 5%; etc.