Adhesion can be measured by a test method called a Peel Test. A peel test indicates how strongly the pressure sensitive adhesive has bonded to the substrate. Typically, peel strength is measured for initial and ultimate adhesion. Initial adhesion indicates how well a pressure sensitive adhesive has bonded to a substrate after a short period of time, usually seconds or minutes. Ultimate adhesion refers to a pressure sensitive adhesive’s bond strength after 72 hours.