Idk if this is really off topic but whatever.

Correct me if I am wrong, but I believe that the only thing inside of "normal" glass that makes it block UV is trace iron impurities. I believe those iron impurities are also what gives many glass products their distinctive teal-green tint if you look closely. Therefore (again if I am thinking correctly), covering a harmful UV lamp with glass that looks teal will provide UV shielding while covering it with glass that looks more bright and clear has a risk of not sufficiently shielding against UV.

Lots of people here use drinking glasses as shields against smaller UVC lamps like the quartz cold cathode ones and the smaller hot cathode ones like the G4S11 and GTL3. But not all drinking glasses have higher iron content, many of by (some fairly thick) glasses at home have no visible teal coloration at all, meaning they might not provide protection.

Has anyone ever encountered this?

That is a good question

How do we experiment with the glass in question between UVC transmitter and the known UVC excitable material?

For sure, it is not the brightest idea to use some random glass for critical UV protection. But I believe to block 254nm UVC completely just a little amount of impurities is necessary, much below the quantity that causes a visible tint. But, when measured thoroughly, many kinds of glass leak certain amount of UVB. Fortunately, not as dangerous wavelengths as 254nm UVC, though still not advisable for prolonged exposure.

 

You could probably use UV test cards to test your glasses.