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
Selfportrait at 6th wedding anniversary 1988 and is today at the Paula Modersohn-Becker Museum in Bremen, the first museum devoted to a female artist. Selfportrait at 6th wedding anniversary Self-Portrait on the sixth anniversary of marriage was painted in Paris. She had moved from Worpswede near Bremen in Germany in February 1906. Modersohn-Becker had decided to leave her husband and Worpswede forever, and devote herself entirely to art. This self-portrait was painted in the spring. She is turned to the right in front of the viewer and she watches the viewer with a searching and questioning look. She has a white cloth on her hip.