From Gardener's Supply (www.gardeners.com)

Care and Maintenance of Teak Kitchenware

Our teak kitchenware is made from cross-cut slabs of sustainably-harvested Costa Rican teak. The size, thickness and color of each coaster varies; each one is unique.

We recommend cleaning the trivets occasionally with a mild detergent, such as Simple Green, a nontoxic, non-abrasive and biodegradable cleaner that is good for removing grit, dust, or soap build-up. It also helps keep the finish smooth and uniform in color. After several years, the teak may gradually turn silver-gray. To restore the original golden teak color, sand the wood lightly. The coasters can be refinished with an organic or environmentally friendly sealer or finish, such as mineral oil.