What activates the inner layer of fiberglass tape in cast application?

• A. Cold water
• B. Warm water
• C. Soap and water
• D. Air exposure

Answer: (B)

Fiberglass cast tape uses a resin binder that needs moisture to start the curing process. When moisture is applied, the resin polymerizes and the tape hardens into a rigid shell. Warm water is recommended because it speeds up this reaction, leading to faster and more even setting. Cold water would activate the resin too, but more slowly, which can delay the cast’s hardening. Soap and water can leave a film that interferes with proper bonding and curing, so they’re not ideal. Exposing the tape to air provides no moisture, so the resin won’t activate and the cast won’t set correctly.