WF300 Caulk is a latex based, high solids firestop caulk. This material, when properly installed, effectively seals penetration openings in wood frame construction against the spread of fire, smoke and combustion by-products. WF300 Caulk is a single stage intumescent. When exposed to elevated temperatures, WF300 expands rapidly to seal off voids left by the burning or melting of combustible materials. WF300 Caulk is storage stable (when stored according to manufacturer’s recommendations) and will not separate or shrink when dried. WF300 adheres tenaciously to common construction materials such as lumber and gypsum board as well as typical penetrant materials. Economical – delivers maximum fire protection at the right price. Water-Based – easy installation, clean-up and disposal. Water-Resistant – will not re-emulsify. Intumescent – expansion fills gaps or voids caused by wood shrinkage, or burning or melting of combustible materials. Meets ASTM E814 (ANSI/UL 1479). Acoustically tested – reduces noise transmission.