Making glass-to-metal seals for homemade vacuum tubes.

A hobbyist documents experiments making vacuum-tight glass-to-metal seals for homemade vacuum tubes using borosilicate glass. After testing copper, iron, plated steel, tungsten, foil, and disc seals, they find tungsten wire up to 0.7 mm and thin copper disc seals work, with thermal expansion mismatch as the main challenge.