Coppersmith extensive degree it must be annealed. This process involves heating the metal and then rapidly cooling it in water. The cooling stage is known as quenching. By heating the copper, the molecules in the metal are relaxed, and thus able to align themselves in a more uniform fashion. This allows for easier shaping of the metal. In order to keep this uniformity within the metal, it is cooled instantly. This prevents the molecules from moving around and causing tension in the structure of the metal. Unlike ferrous metals—which must be cooled slowly to anneal—copper can be cooled slowly in air
Glass-to-metal seal tube is insensitive to high electric current compared to a Dumet-seal because on heating the tensile stress converts into a compression stress which is again limited by the tensile strength of the copper. Also, it is possible to lead an additional solid copper wire through the copper tube. In a later variant, only a short section of the copper tube has a thin wall and the copper tube is hindered to shrink at cooling by a ceramic tube inside the copper tube. If large parts of copper are to be fitted to glass like the water cooled copper anode of