The casting of the first mirror, in a rotating furnace, was completed on November 3, 2005, but the grinding and polishing were still going on 6½ years later when the second mirror was cast, on 14 January 2012.
第一面鏡子於2005年11月3日在旋轉爐（英语：rotating furnace）中鑄造完成，但在6年半之後，第二面鏡子在2012年1月14日鑄造時，還在進行研磨和拋光。