In 1913, Crookes created a 100% ultraviolet and 90% infrared blocking lens made from glass containing cerium, but only lightly tinted. They were an unintended by-product of Crookes's research to find a lens glass formulation that would protect glass workers from cataracts. Crookes tested more than 300 formulations, each numbered and labelled. Crookes Glass 246 was the tint recommended for glassworkers. The best-known Crookes tints are "A" (withdrawn due to its uranium), "A1", "B", and "B2", which absorb all ultraviolet below 350 nm while darkening visual light. Crookes' samples were made by Whitefriars, London, stained glass makers, and Chance Brothers, Birmingham.