Glass tube is the most material in making a neon sign. Tube size approximately 8-15 mm in diameter are heated in portions using many kinds of burners.
The burners have ribbon, cannon or crossfires and also a number of torches that work on a basic mixture of butane, propane or natural gas and air. An electrode is melted to each tip of the tube when it is done.
The electrodes are made of lead glass which has a little metal shell with two wires covering through the glass in which the wires of the sign will be connected.
All attachments should be seamlessly put together without any leaks before going to the next task. Then, the tube is put to a chamber which is connected to a well-made vacuum pump. The air in the neon tubes will then be removed. When removing the air, a high current is inserted through the tube through wires covering the electrode. This is called the bombarding process. The flow of electricity depends on the type of electrode used and the size of the tube. It is usually from 500mA to 1000mA level, at an applied voltage typically from 15,000 to 25,000V.
The bombarding transformer serves as an adaptable and steady electrical source. The length and pressure of the tube determine voltage being created. Basically the operator will regulate the pressure depending on the capacity of the bombarder to secure the loss of energy during the heat conversion process.
This sounds all high tech and complicated but nevertheless, this is how neon signs are made.