How is the gas neon put into the tube used in neon signs?

Answer 1

The finished sign tube, complete with its electrodes, has a "port" in it where a vacuum pump is attached and all the air in the tube is removed. After the tube is pumped down to remove air, it is energized to heat it and drive out remaining air. Then a "breath" of neon gas is put in, and the glass melted to close the port and seal the tube. It takes very little 'cause the gas in the tube is a very low pressure. Use the link below to a YouTube post and see how it's done. YouTube has additional video clips on neon sign making. Check them out. And if you are interested in how some other things are made, do a search of YouTube and see if something is posted. There are literally thousands of video clips there on how different things are made. Lab experiments, how-to demonstrations and solving math problems are just some of the posts there. Check it out next time you have a problem to solve or a question about how something is done.

Answer 2

Neon tubes are capped off by two glass electrodes that have wire passing from outside to inside. One of these electrodes has tubulation - a small tube which remains as a passage from outside to inside. Tubulations are sealed to a pumping system. The pumping system has glass stopcocks or valves that allow sections to be selectively opened or closed. An ultrahigh vacuum pump pulls air out of the tube while a high voltage transformer bombards and heats the remaining air - to produce temperatures in excess of 500ºF. This allows the tube to achieve a higher degree of purity. When a high vacuum is reached, and the tube begins to cool, a small amount of inert gas is introduced from a flask or a tank of pressurized gas. The tubulation is then heated and as it is pulled it such inward to make the tube's own seal.