Technically, all plywood is plywood veneer. Plywood is an engineered wood. It is created by gluing at least three thin layers of wood, called plies or veneers, together so that the wood grain in each veneer layer is perpendicular to the grain of the previous layer. Plywood veneer is a very strong, durable product.
Veneer is created by shaving thin layers of wood off a suitable log. In the rotary cutting process, the entire log is rotated evenly while held against a long blade. It is the most efficient method of cutting veneer and results in the largest sheet. In the flat cut method, layers are cut from one side of a stationary log. This often results in beautiful grained veneer.
The veneer can be made from rotary cut or flat cut veneer. The important element of the veneer is that each layer is placed so that the wood grain is at a 90 degree angle to the wood grain in the previous layer. This placement gives the veneer its unusual strength. Because wood tends to crack, swell, shrink, and warp along the grain, having the grain in each layer run the opposite way reduces wood movement.
The glue used in plywood is also critical to the strength of the finished plywood veneer. Although the use of veneer dates back to ancient Egypt, it had a limited range of use, primarily ornamental. The available glue was not durable enough for heavy use.
Synthetic resin adhesives were developed in the 1920s and continued to improve through the 1930s. It was then possible to fully appreciate the strength of plywood. One of the famous fighter planes of World War II, the British mosquito bomber, was affectionately called the "wooden wonder" because it was made of plywood. The use of plywood increased dramatically during the post-war years.
Better glues are still being developed for plywood veneer. Today, the emphasis is on creating glue that is nontoxic and is appropriate for a particular use. Indoor, outdoor, and marine plywood are made with different glues. It is also possible now to impregnate the veneer layers with plastic, creating a product suitable for even more projects.
Plywood veneer has many benefits. It has greater static bending strength than steel, when the two are compared pound for pound. It is made from a renewable resource. It wastes less of the log than cutting lumber does. It is enormously versatile, used in everything from floors to musical instruments to airplane propellers. It is beautiful, displaying the attractive color and pattern of highly prized hardwoods. Because of these benefits, its popularity continues to increase.