Going through my antique vacuum tubes part 2

The actual glass vacuum electrodes generally do NOT contain inert or noble gases as many people claim. The color and effects of the discharge are created from normal air at various vacuums. While sparks in normal air are are purple, these sparks spread from red, violet, blue, lavender, and white as the vacuum inside of the tube increases:

Some manufacturers did use Neon in their electrodes, but this was mainly limited to European devices from the 1930s and later. Most American devices simply used ambient air at various degrees of vacuum. The photos above are of of the same glass tube, however the vacuum is steadily increasing from left to right. If the white vacuum on the far right was evacuated even more, the various discharges of Crookes and Röntgen would start to appear.

One of the last misconceptions about Violet Rays is that they emit ultraviolet radiation. This is also false. Quartz Glass is the only glass that can transmit Ultraviolet Radiation, and most Violet Ray electrodes are made from Pyrex or Soda Lime Glass. The only Ultraviolet Radiation emitted from these machines is from the actual sparks generated from them. All electric sparks produce Ultraviolet Radiation to some extent. The only effect of the gas, pressure, or vacuum inside of glass the electrodes is the actual resistance of the vacuum electrode and the this effects the characteristics of the electricity conducted through them. As the old manuals boast, "the electrodes diffuse the electricity". In other words, they remove the harshness associated with a direct electrical spark to the body.