When coke replaced wood for kilning malt in the late 17th Century, it became possible for British brewers to produce lighter colored ales. But brown ales, milds and porters were still the preferred styles. By the late 18th Century, while Londoners were still focused on porters and milds, brewers up north in Burton-on-Trent began producing pale ales. The hardness of the water in Burton accentuated the hop character of these pale ales and some began to refer to these paler, hoppier beers as bitters to distinguish them from the milds. By the late 19th Century, bitter had surpassed porter and milds as England's preferred tipple.