A rushlight is a type of candle formed using the dried pith of the rush plant as its wick. The green epidermis or rind is peeled off to reveal the inner pith, aside from a single strip left to provide support. It is then steeped in any household fat or grease that is available although beeswax or good tallow, especially mutton fat, improves the quality of the light. In particularly thrifty households two strips of epidermis are left, reducing the light output but extending the life of the rushlight. On more remote Atlantic islands such as St. Kilda the stomach oil produced by Fulmars was used as the source of oil.
Before paraffin wax candles started to become readily available, true wax candles made from beeswax were expensive and the preserve of the rich. A rushlight provided very economical lighting for the less well-off. A rushlight 2/3 of a metre long (about 2 feet) might burn for an hour and cost practically nothing to make.