The 100-inch telescope mirror at the Mount Wilson Observatory in California was originally coated with silver. Silver, however, loses its polish easily, and it was necessary to replace the foiling twice yearly.

• 加利福尼亚州威尔逊山天文台的100英寸望远镜镜面原先涂的是银粉，但是银粉很容易失去光泽，因此每年都得重新涂两次。