Why can platinum wire be sealed by glass?

Incandescent light bulbs need a wire is needed to carry the electrical current inside the bulb to the tungsten filament and get very hot when operating. read more

The bulb is filled with inert gas to prevent the filament from burning (no oxygen) , so a good seal is needed between the glass and the wire. If the wire and the glass expanded at different rates, the seal would be broken. Brass expands at. 18.7×10−6m. for each metre of length if its temperature changes by. 1 K. Plate glass only expands. 9.0×10−6m, which is the same expansion rate as platinum. Since both the glass and the platinum move at the same rate, the seal between then is undamaged. read more

Platinum is one of many choices, and not the best. The two requirements of a glass to metal bond are that the molten glass wet the metal, and that the thermal expansion coefficient of the metal be similar to that of the glass. read more