Ply comes from the French word plier, which means to fold and be layered.
Each sheet of plywood is a combination of wood fiber and resin. They're stacked so that the grain of each layer is set perpendicular to the ones above and below it, making the strength of the panel consistent in all directions.
We might think of plywood as a modern invention, but the ancient Egyptians and Greeks also sliced wood and glued it together in perpendicular layers for building.
In 1850, Immanuel Nobel — father of the creator of the Nobel Prize — created a revolution in plywood production with his mechanized rotary lathe. It peeled a single log into continuous sheets, like a paper towel unreeling from its roll.
Today, plywood production starts with a long straight log — usually cedar, pine or oak — that is debarked and then heated to make it more flexible. After the logs are cut into smaller pieces, a rotary lathe peels them into thin sheets called veneers. Those are then glued together and baked under high pressure to form the plywood panel.
Many of those adhesives contain formaldehyde, which can be carcinogenic, so manufacturers are now moving toward less toxic chemicals.
And certifications now exist to maximize sustainable production practices, energy efficiency and forest conservation.
The next time you pick up a 4x8 sheet of plywood at the hardware store, keep in mind that it’s not only composed of trees, but also a long history of innovation.
