out the hops—see Burtonisation. Much of the open land within and around the town is protected from chemical treatment to help preserve this water quality. The town is still home to seven brewers: Coors, a brewery from the United States which produces Carling. In addition to their large-scale plant, Coors also operate the White Shield Brewery, a microbrewery producing a number of speciality beers, including the eponymous Worthington White Shield. Marston, Thompson and Evershed, now Marston's PLC. Marston's also brew Bass beer and Stones Bitter under licence from Anheuser-Busch InBev Burton Bridge Brewery, a small brewery founded in 1982 by Geoff Mumford and Bruce Wilkinson. Tower Brewery, a microbrewery Cottage Brewery, its retail outlet being the nearby Old Cottage Inn Black Hole Brewery, a microbrewery subsidiary of Kammac, a cask supplier The Bass Museum of Brewing—renamed the Coors Visitor Centre after Coors took over the brewery—continued until June 2008. This was reopened in 2010 as the William Worthington Brewery and its ales—including Worthington Red Shield, White Shield, and "E", are primarily sold through the on-site Brewery Tap outlet. A by-product of the brewing industry, figuratively and literally, is the Marmite factory in the town: Marmite being made from spent brewer's yeast. Together with the breweries this can give the area a distinctive smell. A pale and well hopped style of beer was developed in Burton in parallel with the development of India Pale Ale elsewhere. Previously, Englishmen had drunk mainly dark stout and porter beers, but pale ale came to predominate. Burton came to dominate this trade, and at its height one quarter of all beer sold in Britain was produced here. Although over thirty breweries are recorded in 1880, a process of mergers and buy-outs resulted in three main breweries remaining by 1980: Bass, Ind Coopes and Marston's. The fame of Burton ales gave rise to the English euphemism "gone for a Burton" during World War II, meaning to be missing or have died. The town's connection with the brewing industry is celebrated by the sculpture of the Burton Cooper in the shopping centre. Burton upon Trent is also known in beer technology circles for the Burton Union recirculating fermenter system, now used only by Marston's Brewery (all other Burton brewers have switched to stainless steel). Home brewing Since 1963 it has been legal to brew any amount of beer at home, without a licence, providing it is not