The faster the movement of molecules, the more fluid the glass. As the glass cools and contracts, the molecules slow down. If the glass cools unevenly the molecular structure will be unstable, leaving stress in the glass. This often results in cracking or breaks. After a series of bends have been completed to form a particular shape, electrodes are welded to each end.
Electrodes are metal shells encased in glass with wires on the end.
Now, the tube is ready to be filled with gas. The tube is hooked up to a vacuum pump and all the air is pulled out. At the same time, it is hooked up to a bombarding transformer and heated using electricity. As the tube gets hot, gases and impurities in the tube are released and pulled out by the vacuum pump. When the desired vacuum and temperature are achieved, the tube is filled with gas and sealed closed.