A collapsed 13th-century window, discovered during archaeological excavations in Carmarthen, Wales, was lifted using polyurethane foam. Much glass remained in the window leads but had decayed badly and was wet, opaque, and blackened. The leads were in good condition. After tests with various consolidants the glass was successfully treated with Primal WS-24, an acrylic colloidal dispersion. As a result of the treatment leaded glass pieces could be safely repositioned to obtain the original window design. -- AATA