The time between applying the adhesive and the formation of a skin on its surface, after which bonding can no longer take place.

• A. Substrate
• B. Skin Time
• C. Tensile strength
• D. Solvant

Answer: (B)

The main idea here is the period called skin time—the window after applying the adhesive when the surface stays workable and can still form a bond. With windshield urethane, the adhesive starts to cure from the surface inward, and a skin forms on top. Once that skin appears, the adhesive won’t wet or bond properly to the glass or the frame, so bonding after this point is ineffective. Temperature, humidity, and the adhesive formulation all influence how quickly that skin forms, so you have to bond within this time frame to ensure a strong, proper bond. The other terms describe different concepts: substrate is what you bond to, tensile strength is a property of the cured bond, and solvent relates to chemicals used with the adhesive, not the bonding window.