How To Do A Label Marking Durability Test [Video and Infographic] How to Do an Isopropyl Alcohol Rub Test What you'll need: Isopropyl Alcohol Toothbrush Timer Immerse your label in isopropyl alcohol for 3 minutes. Remove the label from the alcohol. Then, use a toothbrush to scrub the impression 10 times. Repeat steps a-b twice more for a total of 3 cycles. Review the label impression for degradation.