a variety of names, is a transparent plastic, in piercing mostly used for plugs and tapers. Due to the material's smoothness, it has been used for stretching. Many overenthusiastic wearers have damaged their holes with acrylic tapers. It is not a safe material for damaged or new piercings and can not be heat sterilized by autoclave as it can melt or discolor. Acrylics can emit carcinogenic toxins above 70 degrees Fahrenheit (21° Celsius), which normal body temperature is above. It is also a fragile material and can easily crack, craze or shard if dropped. Jewelry made of acrylic has a tendency to collect body fluids and skin parts in tiny pores and fissures. The Association of Professional Piercers suggests that it may only be used for temporary wear in healed piercings. Acrylic can be a chemical irritant or allergen, resulting in Acrylic monomer dermatitis from the decomposition of methyl methacrylate. Gems Gems or gemstones are mostly used as inlays in plugs and as beads in BCRs. The quality varies widely with different gems, and it can be hard to find stones big enough without cracks and scratches. Some stones may affect the body such as malachite which contains copper that can discolor the skin. Others may contain lead or arsenic or other hazardous materials. However, stones are generally not a problem for the body as long as they don't have sharp or pointy edges or are not very heavy. They can most of the time be autoclaved, but some stones, such as opals can't stand the heat and should be cleaned some other way. See Gemstones Natural materials Wood Wood is a common material for plugs and other shapes. Wooden pieces tend to keep warm in cold conditions, they are lightweight, they often stay in place better than other plugs and also they allow the body to "breathe" so the piercing is less likely to smell as it might with other materials. The downside of wood as body jewelry is if not cared for properly it may dry out and lose luster. This can be prevented with mineral oil or jojoba oil and avoiding excessive exposure to water. It should not be autoclaved as that can cause cracking, warping, or splitting. Wood has grain that will rise if not properly finished, dramatically changing the texture. The porosity of wood and inability to be safely sterilized renders it inappropriate as a