Litharge: Lead Oxidised in Air, Then Fused

Melted lead left open to the air grows a yellow skin of lead oxide. Melted again, that oxide sets into reddish-yellow scales: litharge, the drier in boiled oil and a flux for glazes and glass. Andrew Ure (1839) describes both steps; in the silver works it ran off the hearth where lead was refined. Lead oxide is poisonous: work outdoors. The picture: the two forms of lead oxide, red litharge and yellow massicot.