At  and below, pure tin transforms from the silvery, ductile metallic  allotrope of β-form  white tin to the brittle, nonmetallic, α-form grey tin with a diamond cubic structure. The transformation is slow to initiate due to a high activation energy but the presence of germanium (or crystal structures of similar form and size) or very low temperatures of roughly −30 °C aids the initiation. There is also a large volume increase of about 27% associated with the phase change to the nonmetallic low temperature allotrope. This frequently makes tin objects (like buttons) decompose into powder during the transformation, hence the name tin pest. The decomposition will catalyze itself, which is why the reaction accelerates once it starts. The mere presence of tin pest leads to  tin pest. Tin objects at low temperatures will simply disintegrate.