In the late 18th century, Samuel Bentham discovered that by gluing together separate thin pieces of wood he could form a composite piece of timber that was stronger than a length of wood cut straight from a log. He registered a patent for the idea in 1797 but, because his process used hand-sawn timber, what he produced was rather rough and its final size was limited by the size of the timber that was used to cut the thin planks that were stuck together.
However, in the middle of 19th century, Immanuel Nobel - the father of Alfred Nobel - invented a rotary lathe that produced relatively large sheets of thin wood by rotating a trunk or branch while holding a long blade against it that was under tension. Large sheets could be cut or peeled away from relatively thin trunks of trees as long as they were fairly straight and the grain was not too distorted around secondary branches. These thin sheets were then glued together with alternate sheets turned, so that the grain ran across at 90 degrees, and it was then dried by baking under pressure to keep the composite sheets of timber flat.
Industrial production of plywood started in France in the 1860s and the process was introduced to the USA about 1865. The main products - large timber sheets of various thickness - are used as a building material in construction to line the walls and roof or plywood can be used for shuttering for poured concrete.
With glue that is resistant to damp and mould, plywood can be used for boat building and in the 20th century it’s lightness and strength made it ideal for the construction of the frames of early aircraft.
For furniture, plywood can be sawn and sanded, using normal wood-work tools, although some care has to be taken when using a plane. When finer veneer, from an exotic tree or veneer with an ornate grain is used on the outer faces, plywood can be used in large sheets for cabinet doors or the sides of cupboards although thinner sheets have to be supported on some form of framework. Large sheets of plywood are used for the backs of furniture and the bottoms or even the sides of drawers but thicker plywood can also be used effectively for worktops and table tops where the alternate light and dark layers - the consequence of laying alternate sheets in alternate directions - can make a distinctive and decorative edge.
Plywood, when heated or steamed, can be bent or curved and, if held in that form while it is dried or it is heated, then it retains the shape.
In Finland, although the native birch does not grow to a particularly substantial trunk it has a good regular grain and, when used for plywood, is much stronger than plywood made from softwood ply and the properties of plywood have been well-exploited in building construction and for furniture production.
Birch trees in a Finnish wood