Things You'll Need
3/8-inch flat plywood
Rotary cutting mats protect your work surface from damage while also providing convenient measurements, cutting lines and angles. However, when the mat warps from improper storage or from being overheated, it loses most of that usefulness. While there is no guaranteed way to flatten these mats again, you may find that you can straighten them enough to continue using them.
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Taking It Outside
Place the wood sheet on a hard surface that will hold heat, such as a concrete patio, in an area that will receive full sun for several hours.
Position the warped mat on the plywood.
Cover the mat and wood with a piece of plate glass. Leave this corrective sandwich in the sun for the day.
Allow the glass, mat and wood to cool overnight.
Turning on the Cold
Place two metal cookie sheets in the freezer for at least an hour or until the sheets are very cold.
Sandwich the mat between the two cold metal sheets.
Weight the stack with something heavy. Large cans of vegetables or other foods make convenient weights.
Leave the mat between the metal sheets until they return to room temperature. Check the mat's flatness and then repeat the process, if necessary, until the mat is flat.
To prevent warping, always store your mat flat or hanging. Don’t iron on it and don’t store it over a heating vent. Move the mat before placing hot foods or drinks on the work surface.
Even after the mat looks flat again, don’t trust the measurement grid until you have checked its accuracy.