A short web article explaining why the pewter inlay on antique bobbin lace bobbins swells, crumbles or falls off. It describes pewter as a tin-lead alloy and attributes the damage to "tin pest" or tin disease, in which tin changes form below about 13 degrees C. It also discusses the folklore that pewter-spotted "leopard" bobbins were made to ease arthritis, and offers advice on storing bobbins.