Thermometers commonly used in home brewing fall into three broad categories - the traditional liquid (alcohol or mercury) type; dial thermometers; and digital thermometers. Liquid thermometers are reasonably accurate, but have the disadvantage of being fragile; furthermore, mercury is highly toxic -- the use of mercury thermometers in brewing is not recommended. Dial thermometers are reasonably rugged, usually liquid-proof, and respond quickly, but may suffer from poor accuracy. Digital thermometers are available in a wide variety of styles and price ranges; the cheapest digital models generally cost around $15, are typically not liquid-proof, and are plenty accurate enough for mashing.