Plywood is a sheet material manufactured from thin layers or "plies" of wood veneer that are glued together with adjacent layers having their wood grain rotated up to 90 degrees to one another. This configuration greatly enhances the material strength and reduces expansion and contraction due to humidity changes compared to solid lumber. There are usually an odd number of plies so the plane of symmetry is in the central ply; also staves may separate under pressure or moisture if not cross-banded.

Manufacturing Process

The Plywood begins with selection of the wood species that will be used for the face and core plies. Commonly used species for the face layers include birch, poplar, mahogany, oak and maple while the core layers are generally lower grade woods like spruce or pine. The logs are sliced into sheets of veneer about 1/50th of an inch thick using a rotary lathe.

The veneer sheets are dried and graded before being laid out in the desired orientation for pressing. Adhesives such as phenol formaldehyde are applied and the plies are stacked and placed in a hydraulic press which applies both heat and pressure to bond them together. After pressing, the newly formed panel is trimmed to size and sanded smooth before being sorted or stacked for shipment.

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