safety instructions, allowed materials and components as well as testing methods such as tensile tests for PVC bottles. Most regulations applied to a country are generally harmonized in order to be applied and applicable in a larger area, such as a trade zone. Problems There have been problems with premature failure of rubber hot-water bottles due to faulty manufacture. The rubber may fail strength or fitness tests, or become brittle if manufacturing is not controlled closely. Natural rubber filled with calcium carbonate is the most common material used, but is susceptible to oxidation and polymer degradation at the high temperatures used in shaping the product. Even though the brittle cracks may not be visible externally, the bottle can fracture suddenly after filling with hot water, and can scald the user—sometimes requiring hospitalization for severe burn cases. Boiling water is not recommended for use in hot-water bottles. This is due to risks of the rubber being degraded from high-temperature water, and the risk of injury in case of breakage. Hot water bottle rash (Erythema ab igne) is a skin condition caused by long-term exposure to heat (infrared radiation) or excessive use of a hot water bottle. In fiction Alfred, the cantankerous hot-water bottle, is a character from Johnson and Friends, a popular Australian children's television series from the 1990s. This character has gained a cult following in recent years, particularly among those who grew up with the series, due to the odd character choice. Another anthropomorphised hot-water bottle was Walter Hottle Bottle in the British children's comic Jack and Jill. See also Hot water bottle blowing References External links Bottles Medical equipment Medical treatments Heating Food preservation Croatian inventions