Wood warping

Wood warping is a deviation from flatness in timber as a result of stresses and uneven shrinkage. Warping can also occur in wood considered "dry" (wood can take up and release moisture indefinitely), when it takes up moisture unevenly, or – especially – is allowed to return to its "dry" equilibrium state unevenly, too slowly, or too quickly. Many factors can contribute to wood warp; wood species, grain orientation, air flow, sunlight, uneven finishing, temperature – even cutting season and the moon's gravitational pull are taken into account in some traditions (e.g., violin making).

The types of wood warping include:

Wood warping costs the wood industry in the U.S. millions of dollars per year. Straight wood boards that leave a cutting facility sometimes arrive at the store yard warped. This little understood process is finally being looked at in a serious way. Although wood warping has been studied for years, the warping control model for manufacturing composite wood hasn't been updated for about 40 years.

A researcher at Texas A&M University, Zhiyong Cai, has researched wood warping, and was working on a computer software program in 2003 to help manufacturers make changes in the manufacturing process so that wood doesn't arrive at its destination warped after it leaves the mill or factory.

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