Teak is a dense, coarse, close-grained hardwood. It naturally contains high levels of resinous oil that acts as an insect repellent and allows it to be resistant to moisture and the drying effects of weather. Teak also contains silica, which creates a density to the wood that allows it to be resistant to fungal decay, water, rotting, warping, shrinking, swelling and many chemicals. Teak is easily worked and has natural oils that make it suitable for use in exposed locations, where it is durable even when not treated with oil or varnish. Teak cut from old trees grown slowly in natural forests is more durable and harder; teak from young trees grown in plantations is more prone to splitting and water damage, however kiln drying allows for sustainable, plantation-grown teak to perform nearly on par with old-growth teak.