What is the difference between cohesive / adhesive failure and why is this important?
Cohesive failure – bead cracks or tears down the center. Possible causes: (1) 3-point adhesion – bead adheres to back of joint which prevents good flexibility and elasticity between the joint substrates. Solution: Recaulk over existing bead (2) Oils, etc. in a paint or stain causes bead to “dry” and “crack” – product incompatibility. Solution: use a product that is compatible with the caulk. Adhesive failure – caulk bead does not adhere to one or both of the substrates to which it is applied. This is a more difficult problem to solve. Possible causes: (1) product incompatibility with a paint, stain or previous caulking (silicone) which has already been applied, (2) incompatibility with the substrate itself (some rubbers, polypropylenes, polyethylene’s, neoprene, some oily woods, teflon, waxy surfaces, etc.), or (3) application error (not enough product applied to withstand joint movement, poor tooling, etc.). Solution: Caulking bead usually needs to be removed (see question #13), the s
