Kyrkofönster Watch: Sigmar Polke

For the Zurich windows, an abundance of techniques will be employed,\nincluding the oldest: the mixing of metallic oxides--such as copper for\nruby red, manganese for rose pink, and cobalt for blue--with molten\nglass. (That was the predominant practice until about 1300, when it was\ndiscovered that silver-nitrate solution brushed onto glass stained it\nyellow, giving the medium its name.) Others will be flashed-glass\nabrasion (clear panes fused with colored ones which are scraped away to\nvarious results), glass fusing (combining layers of different-colored\nglass), sandblasting, and a traditional procedure called Schwarzlot,\nthe manipulation of black enamel with hand tools that yield delectable\nnames in translation: expellers, draggers, pestles, quills.