Marine Glues, what is WBP
Glues used in exterior and marine plywood that will be exposed to water and weather is described as WBP (Weather and Boil Proof). This only means that a plywood sample glued with this adhesive does not delaminate after a prolonged period of boiling. It is NOT a description of the type of glue. WBP only describes its characteristics. Several glues have proved to be WBP.
Most WBP glues are either melamine or phenolic glues. Lower quality melamine plywood can sustain 4-8 hours boiling without delaminating. Higher end melamine can last between 10-20 hours in the boil test.
Phenolic plywood is considerably more resistant (24-72 hours). The best phenolic glue can be regarded as essentially permanent adhesives and are used in the higher grades of Marine Plywood.
Various organizations have set up standards for the testing of glues and marine plywoods must conform in order to be able to claim conformance to the marine plywood standards.
It is likely that under sustained boiling, plywood plies glued with high end phenolic adhesive, will fail before the glue. It is therefore important to consider the ply quality and manufacture quality along with the quality of the adhesive. No amount of quality WBP will keep a poorly manufactured panel made with inferior plies together.
Marine Plywood Grades
In order to be a Marine Grade the plywood has to conform to a certain number of criteria:
The Glue MUST be waterproof
Voids are to be avoided
Face and inside veneers have to be good
