Glass is often thought to be everlasting, but this is not the case. Even glass disappears with time. It starts to disintegrate under the influence of air and moisture, and the glass objects found in archaeological excavations often are badly weathered. This decay in glass is called iridescence. Iridescent glass is brittle and it sparkles in all the colours of the rainbow. The decay of glass cannot even be stopped after its recovery from the soil, and thus also the glass objects in the museumΓÇÖs collections continue to deteriorate. Amongst old finds, window glass and forest glass of poor quality are particularly susceptible to iridescence.
