Tanbark is a natural wood product formed from the outer layers of the tanbark oak tree, a close relative of the popular hardwood species known as true oak. The tree is prized primarily for its abundance of tannins, organic chemicals used during the hide and leather tanning process. The tannins contained in the oak's outer layers are mechanically removed, leaving behind a dry wood product suitable for mulching. In recent years, however, the tanning industry has largely replaced these natural tannins with synthetic ones.
This has not lessened the popularity of spent tanbark as a ground covering in such places as circus arenas, horse tracks, and children's playgrounds. It is often placed around playground equipment for the purposes of shock absorption and all-weather maintenance. For circuses and other public arenas, tanbark provides an inexpensive floor covering ideal for providing traction for visitors and shock absorption for performers and animals.
The use of tanbark in playgrounds has been recommended by industry experts for years, but recent studies have suggested that other materials such as shredded recycled rubber may be just as effective. The main concern is not the natural shock absorption qualities of the bark itself, but rather the difficulty of maintaining minimal depth levels for maximum protection. The correct level is often placed around new playground equipment, but eventually the tanbark becomes compacted or scattered. Only regular replenishment of the material can ensure the playground meets the industry's safety standards.
Another concern with the use of tanbark is the potential for insect infestation or other contaminants. Natural wood products make attractive targets for termites, for instance, so routine replacement of the covering should be a standard practice for playground maintenance workers. When used in playgrounds, it should not be heavily treated with chemicals such as arsenic, although testing may be necessary to determine if any harmful chemicals have leached into the ground from treated ground covering.