Tin pest related problems such as tin whiskers. At 13.2 °C (about 56 °F) 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
The Anniversary (Fawlty Towers) The Anniversary (Fawlty Towers) "The Anniversary" is the fifth episode of the second series of BBC sitcom "Fawlty Towers". As in other episodes, the letters of the sign for Fawlty Towers are shown rearranged in the opening sequence. In this episode, it says "Flowery Twats". The use of the obscene word has caused this to be given a 12 certificate by the BBFC, which is the only episode in the series to have a more restrictive rating than PG. On the morning of their wedding anniversary, Sybil recalls how Basil forgot last year. Basil has secretly invited their closest friends