environmentally-friendly fuel that does not leave a residue or soot. Denatured alcohol is commonly available at camping outfitters and hardware stores. Denatured alcohol is toxic to drink. Non-toxic pure ethanol is rarely used as stove fuel in the United States, since it is usually subject to a liquor tax. However it also has some medicinal use in treating stings and bites, as a coolant, and antiseptic. These stoves operate marginally on 90% isopropyl alcohol, poorly on 70% and not at all with 50%. Water typically cannot be boiled with isopropyl rubbing alcohol, but if the more rarely found (still inexpensive) laboratory grade or "gas drier" is used, and the sooting is dealt with by applying a little soap solution to the pot, the fuel value of the alcohol will reduce boiling times, not increase them. Variations Standard The classic ultra-lightweight backpacking stove. Designed for one person, lighter than commercial models of the same design Inverted two-piece Smaller and lighter than the standard version; difficult to fill Side-burner Doubles as its own pot stand (holes are in the side). A tight-fitting pot can increase fuel pressure Pressurized A more powerful version. A hole in the top of the stove is sealed with a thumbscrew after filling with fuel; this allows the stove to control the rate of heat output. An additional base is used to hold fuel for preheating Back-pressured Back-pressured stoves simplify the pressurized design by eliminating the thumbscrew and the base needed for preheating, while still controlling the rate of energy output Insulated A variation on the standard design, with an inner wall and insulated with fiberglass Other Numerous designs in use Multiple-unit More than one unit can be used under the same pot when cooking for a larger number of people Safety issues Alcohol stoves are inherently dangerous, since spilling is possible and the fuel burns with a nearly invisible flame. If a spill occurs the best course of action often is to step back and let the alcohol burn up. A stove with a deep well is wind and blow-out resistant — blowing into it can send burning alcohol flying. A stove with a small, shallow well, or a central wick may or may not be blown out to stop it from burning. A safe and lightweight snuff cap or simmer ring is added to some stove designs. Yet alcohol remains safer than most camping fuels. An