When describing the workings of a germicidal tube (fluorescent-style), many people claim that the envelope is made of quartz to transmit UV-C. However, I have yet to see any molybdenum foil seals in any type of fluorescent or non-fluorescent tube. This suggests that (as I expected) they are just using high-purity soft glass, which makes a lot more sense since high temperatures or high pressures aren't involved.

Has anyone ever seen a quartz UV-C tube? I am not talking about high or medium pressure lamps, just low pressure fluorescent-style lamps.
 

Yes I have a couple of Soviet made F8T5 style germicidals in quartz. Also these modern tiny Chinese CCFL style UVC lamps are quartz made with foil lead-outs.

Quartz is superior, of course, but so are production costs, so it get substituted with uviol glass for mass made lamps.

In Russian there is a verb "To Quartz" (some location etc) which means to sterilize it with UVC. Though the lamp this verb came from is a bare arctube of 125W Mercury lamp, not any type of Fluorescent-like lamp

Sure, but i believe the word actually come from some earlier bare medium-high pressure mercury quartz lamps that were called ПРК (ДРТ) in 250+ wattages and appeared in medical UV irradiator apparatus over about 1930-1950's span.

When describing the workings of a germicidal tube (fluorescent-style), many people claim that the envelope is made of quartz to transmit UV-C. However, I have yet to see any molybdenum foil seals in any type of fluorescent or non-fluorescent tube. This suggests that (as I expected) they are just using high-purity soft glass, which makes a lot more sense since high temperatures or high pressures aren't involved.

Has anyone ever seen a quartz UV-C tube? I am not talking about high or medium pressure lamps, just low pressure fluorescent-style lamps.
 

seen plenty, both in real life and here on LG, but they are only usually seen on cheap Chinese germicidal lamps as Quartz has solarisation issues leading bad UV-C output over time

you can usually tell the Quartz lamps by the fact they have no re-entrant stem next to the cathodes and the PL-S/PL-L types will have 2 little nipples on the end of the tube above the cut-n-kiss joint


(tho somewhere on LG is a GxxT6 slimline quartz germicidal tube with a re-entrant quartz stem assembly )

I have a 8W Narva east german germicidal tube that most certainly is made of quartz as you can see the airlines in it.

seen plenty, both in real life and here on LG, but they are only usually seen on cheap Chinese germicidal lamps as Quartz has solarisation issues leading bad UV-C output over time

Do you have any practical confirmation of this? I always believed the reverse is true, and it is silicate soft glass that blackens over time in UV lamps. At least, high power tubular germicidal lamps like the ones employed in sewage treatment are made from quartz.

I dont know if they are quartz or not but many cheaper lamps get a yellowish tint in the glass over time, which reduces useful UV output. More expensive lamps like Philips TUV dont have this yellowing issue.

I have a 8W Narva east german germicidal tube that most certainly is made of quartz as you can see the airlines in it.

I would not take airlines as an indication its made of Quartz, many of the soft-glass germercidal lamps have airlines in them also, see for example the airlines in this non-quartz lamp

https://www.lighting-gallery.net/gallery/displayimage.php?pos=-84510

instead on the 8W Narva I would look at its end seals and see if they are the molybdenum foil type

Do you have any practical confirmation of this? I always believed the reverse is true, and it is silicate soft glass that blackens over time in UV lamps. At least, high power tubular germicidal lamps like the ones employed in sewage treatment are made from quartz.

see comments here 

https://www.lighting-gallery.net/gallery/displayimage.php?pos=-176865

"Quartz is in fact exceptionally prone to solarization by short waveleng"

I googled a bit and it seems James did not tell a full story there..

There is some complex physics/chemistry in play and while the ordinary melted silica quartz may be prone to quick solarization, process may be adjusted to yield a resistant material, able to withstand 10000+ hours under UVC and remain transparent. That way a proper quartz tubing for low/med pressure UVC lamps and lamp sleeves is made.

https://www.heraeus-covantics.com/media/Media/Documents/Products_and_Solutions/LAMP/EN/Quartz_lamp_materials_EN.pdf
https://iuvaarchives.com/iuva-issues/Vol%2015%20-%202013/Issue%202/150201ArnoldAndAdam_Article_2013.pdf

Interestingly, playing with my own xenon-filled tubes I definitely noticed some soft glass show a reversible blackening, disappearing after a few hours of the rest. Xenon emits a lot of high-energetic UV in the range of 150-170nm, so this almost certainly was some kind of solarization, too.