The Candle Filter is a type of precoat or pressure filter and is predominantly used for clarification of beer that has been fermented and lagered, although other applications, such as sterile filtration or wort filtration, are possible. The name comes from the shape of the filter element, which is a long, thin cylinder that resembles a candle. The earliest type of candle filter was developed by Wilhelm Berkefeld of Germany in the 1890s for water purification. For the brewing industry, candle filters were developed for beer filtration in the 1950s and 1960s. They remain popular today. The candles are mounted inside a cylindrical pressure vessel that receives unfiltered beer. The candle itself is the septum that holds the filter aid, which could be diatomaceous earth, perlite, cellulose, or other materials, during the solid–liquid separation. The candles themselves do not perform any filtration. It is the filter aid which coats the candle that does the actual filtration. Most commonly, candles are fabricated from metal, almost exclusively stainless steel today or ceramic, although other materials are possible. Early candles were composed of stacked washers with small dimples to create a gap between them, allowing liquid but not filter aid to pass through. Today, candles are made from wedge or v-wire and have much greater precision than older types. Unfiltered beer passes from the outside of the candle, through the filter cake, and into the center of the candle. This now filtered beer passes up through a mounting plate or manifold holding the candles and out of the filter housing. Most candles are mounted to the top of the filter housing, but some models have a bottom-mounted candle. For the purposes of beer filtration, there is no difference in the mounting position.