Upon acquiring a high frequency machine which is a skin spot remover but works similar to a neon tester as it has the tesla coil, I did tests on a number of lamps, including vacuum incandescent bulbs. When I pointed the device on the glass, nothing ionizes, of course. But when I placed it on the screw base, they made a dim blue glow that was clinging onto the inner bulb wall. The GE 15w GLS bulbs even had some blue plasma filaments moving around, even though they are vacuum. The other vacuum lamps I tested include a Philips 25w clear made in Mexico and a Candex 40w frost tubular showcase bulb made in Taiwan, both made very little of the blue glow. What could cause that blue glow? It's enough to tell me that there are gases inside these bulbs, but they are not the purplish glow of argon.

Remaining N2 and O2 (Air) molecules inside the outer. Nither artifically made vaccum on earth, is as perfect as the vaccum at the space. Even the vaccum of the space, have microscopic desity of helium and hydrogen and other molecules.

Then the question is, if those lamps are really vacuum orif they are gas filled type.
Indeed the vacuum there is by far of higher residual pressures than in the space, but still it would be wayto low for such discharge forming visible filaments. Theremaining pressure has to be so low, than even with 100%ionization the current is still negligible, otherwise it will form a flashover and by that short circuit the mains.
And another point of view: Thevacuum incandescents are used by many enthusiasts as an available source of X-ray, when excitedfrom a high voltage tesla coil and it works. That mean the vacuum there has to allow electrons to be accelerated to speed corresponding to 10's of kV and that won't create any visible filament discharge.

What does glow there are the electrons hitting the glass surface. But that would visible as really the glass inner surface glowing, no filamentsor other such shapes.

Easy, the electrons were bombarding the glass wall of the lamp causing the glass itself to become fluorescent. I've seen this in radio vacuum tubes that would have blown the power transformer of the set (or a fuse if present) if they were gassy.

Some newer bulbs are pumped with inert gas to keep the filament life longer than in a plain vacuum. They can use neon, argon, xenon, or even krypton. I've used a fly back circuit from an plasma globe and I saw lightning bolt like sparks flying from the filament stems.

Vacuum tube flourscence-see this with some of the RF PA power tubes in some of our transmitters.The tubes run at 15Kv at 9A each-4 in the circuit.Some of them the glass glows-others it doesn't gassy tubes glow from INSIDE the tube elements.Have some of these-esp new ones-cook them on a DC hi pot tester until the gas is cooked into the tube getter.If you try to run the gassy tube in the Tx OL trips and blown transmitter components.The tube tries to act as a THYRATRON tube instead of  a vacuum triode amp tube.Some tubes are so gassy--send them back to their maker.You will only damage the Tx if you try to use them-and the HiPot doesn't cook them out.Sometimes try cooking the tube on the DC HiPot for a few days.This often works.Same with vacuum capacitors.We have an AC Hipot tester here-can't use that on power tubes-it will blow them.Use that for some capacitors only.

Hope this doesn't sound like a stupid question but does the tesla coil thing harm the lamp in any way/is it usable afterward? Can it be done while the bulb is lit?

The Tesla coil can not harm the incandescent at all, but if the incandescent is really a vacuum type, the generated X-ray may harm you...

And for the vacuum tubes and remains of the gases: It is quite common for the tube in long storage to collect some gases. Then you really have to first operate them on limited current source, till teh discharge disappear. What happens is not really the getter, but the gas ions get accelerated and "hammered in" the metal parts, usually the anode (the largest metal part there; it fact it is a form of ionization vacuum pump). In any way, this procedure does clean the vacuum to the extend the lamp could be used again in the real circuit.
When in operation, the same mechanism helps to keep the vacuum clean, but it happens on so low rate, it does not interfere with the normal tube operation.

I also put the fly back transformer on a tiny 12v bulb and it Barely did anything. I could've sworn it produced a tiny amount of x Rays.

I also put the fly back transformer on a tiny 12v bulb and it Barely did anything. I could've sworn it produced a tiny amount of x Rays.

The X-ray depend on the voltage. With most anode materials, you need to go above 30kV of acceleration voltage to generate anything. So to generate any, your flyback would have to reach at least the 30kV or more, that is not that easy on low power levels (except the tuned resonant transformer, a.k.a. "Tesla coil")...
And by the way that is the reason, why tv's were designed with just 27kV of anode voltage - it is below the limit, when it could become an Xray hazard.

The bulb was one of those tiny panel mount e10s that are used in models. I'm pretty sure that it was filled with krypton.

X-rays in older color TV sets-the main X-ray generators in those sets were the HV rectifier tube and the HV shunt regulator tube.These can generate enough X-rays to create a hazard for someone sitting very close to the set.The picture tubes had a leaded glass front panel bonded to the screen-so the X-rays emitted by the tube screen were not a hazard.The only times a CRT can emit X-rays is if the scanning circuits fail and there is a dot or bright line on the screen-the electron beam enery is concentrated on a small area on the tube screen.The HV tubes in TV's were powerful enough to fog dental X-ray film packs put near the HV tubes.So the X-Rays in older TV's can be there.Some TV flyback cages had lead foil ling them where the HVC rect tube and regulator tube are placed.In RCA color sets when you open the flyback cage the HV rect tube is disconeected from the flyback transformer sec winding.
 At our transmitter site X-ray warnings are posted for tubes operating at 15Kv and above plate voltages.One transmitter has a pulse modulator tube running @30Kv 10-20A so the X-Rays from this are dangerous!Operators stay away from the transmitters modulator cabinet and HV section when its operating.In general if a vacuum tube is running at 15Kv and above-X-rays can be present.Gas tubes such as rectifiers it can be even as low as 5Kv.So take care around that HV stuff!If in doubt-use sheilding and stay away from the circuit when it is operating!

The Xray danger is practically not related if the deflection works or not. And if there would be any dependence, the dot will actually radiate less than the full picture. The reason is, the dot heats up the target area and that cause the Xray generation efficiency to drop severely (therefore the Xray tubes use so complicated anode cooling, like rotational anode or so, even when they are operated with rather short "flashes" with quite long gaps between them). Of course all that assumes there is no overvoltage problem at the same time.

And the rectifier tube under normal condition can not emit the Xray, just because there is either no current (reverse; so very little amount of accelerated electrons), or very low voltage drop (forward; the acceleration oltage is few 100's of V). Howeever it can emit Xray when warming up: Because the cathode has insufficient emission, the voltage drop could be the full secondary. And as the secondary is not yet loaded, it has higher voltae than the normal operating level.

And generally the main problem and the real reason for all the shielding or so is in case of voltage regulation malfunction (and it could be caused even by the malfunction of the deflection circuit). Circuit generating normally 27kV could quite easily reach double of that, when "unleashed". And that 50+kV in the event of a failure is, what makes the real X-ray danger and why all that shielding is there.

With the transmitters the situation is partially similar: Normally there is either no current, or low voltage (assume class C stage or so). But the output operation actually doubles the voltage from the supply, so the 30kV is present there with the 15kV supply. And when there is antenna problem, the phase may go wrong in such way, the 30kV meets with the current and you immediately have an Xray.
And when a supply failure is involved on top of that, you easily can end up in the 50+kV range as well...


The fact it fogs an Xray paper means, the dose is still tiny fraction of a single medical Xray "photo", so in other words very low. And I would even guess all that dose collects only during the warmups, when there is temporarily higher voltage than the normal 27kV level...

Incorrect-the X-Rays are generated and present!I have measured them in the transmitter and the TV.Used a radiation survey meter with a non blocking probe.So they are a hazard.In the transmitter modulator stage the X-Rays are most intense when the PDM generator is started after the 30Kv supply is started.For TV's you can get HV rectifiers and shunt reg tubes with leaded sheilding over the glass envelope.Other types of transmitter stages can generate X-Rays-UHF TV klystron and Klystrode tubes.Often these have built in leaded sheilding.Today--of course TVs are no longer an X-Ray hazard.Another possible X-Ray source in transmitters is vacuum capacitors.You can also generate X-Rays with Vac caps during AC or DC HiPot testing.While cooking the gas from a Vac cap-I leave the area and warn others.In one of our transmitters the vacuum tune caps are close to the tranmsitter door-you can detect X-Rays there from the cap.It is operating at 15Kv DC and has RF on it too.Beleive it-the X-rays can be there and precautions taken!Just don't hang around the "hot spots!!"At a closed transmitter plant their tubed PDM transmitter generated X-Rays as well from its modulator.Most hot at the back door of the transmitters mod cabinet.The stage was run at 30Kv.

Yore correct, tolivac. I've seen many vintage arc and plate rectifier tubes with "caution: May emit x rays" included in their etches. I thought that the newer CRTs had a special plastic sheet screen to block out the dangerous waves emitted.