High intensity microwave treatment creates changes in wood structure, and can increase wood permeability by up to several thousand fold.

Inside the wood, microwave energy is converted to heat, creating steam pressure in the wood cells. Under this high internal pressure the thin-walled ray cells rupture to create microvoids in the radial-longitudinal planes of the wood. In hardwoods, microwave treatment also ruptures tyloses (balloon-like swellings that block off older vessels in the heart wood). These microvoids form pathways for easy transportation of liquids and vapours. The pathways allow moisture to escape easily from the wood, helping the wood drying process. They can also be used to assist infusion of resins, preservatives, or coloured stains throughout the wood.

CRC research applications involve adjusting the intensity of microwave energy supplied to control the number of microvoids, their dimensions and distribution. In this way selective microwave modification protocols to suit different applications are developed.

Learn more about microwave energy.

View a simulation of a piece of wood in a microwave field showing how the wood affects the energy distribution.