31C: a glass vessel for storing warmth.
Hollow glass forms containing phase change salts with a melting point of 31C.
In this case we are using a salt that melts at a much higher temperature of 31C.
Winter days in Canberra have clear blue skies and lots of sunlight, but temperatures are frosty . The salts inside will melt in front of a sunny window during the day, and keep the glass at 31C for many hours during the night, providing a place to warm your hands.
Could this test-tube like prototype be extended to a glass Trombe wall containing phase change salts ?