My periodic table poster is now available! Borosilicate glass Medallion. I made this medallion for an article in my Popular Science column, using a charcoal grill to melt old borosilicate test tubes down and press them into a graphite mold. Source: Theodore Gray Contributor: Theodore Gray Acquired: 26 October, 2008 Text Updated: 16 April, 2009 Price: $1 Size: 2.5" Composition: SiO2+Na2[B4O5(OH)4]