Can you touch the tubes?

Since Halogen was brought up, I’ll tell you my experience with 400 watt Metal Halide for Office Lighting.

I designed Corporate Office Space for a living. I was an early adopter and specifier of Furniture Mounted Indirect Lighting for Office Cubies. Very efficient, no reflections of ceiling light fixtures in computer screens, indirect light (bounced off ceilings) light from several directions minimized shadows. Total watts needed for large space far lower than using ceiling fluorescent. Important because many buildings AC systems were already overloaded by then new computers everywhere! Reduce that Lighting Load!

Used them for many clients, including IBM, JP Stevens, CBS several subsidiaries, Time Life, Fortune Magazine, Many Insurance Companies, Lawyers ...

The fixtures had tempered glass covers, lamps had to be replaced, I found out several clients either left the glass covers off, or replaced them with non-tempered glass.

GE issued a bulletin years after they promoted these for office use: these lamps may experience ’non-passive’ end of life (another member mentioned ’non-passive above). I called GE, what the hell does non-passive mean?

Oh, well, the lamp can explode, blasting broken glass up to 2,700 degrees in all directions. Any other questions?

And yes Dorothy, if you got/left any finger oil on them, they could/would explode.

Holy Crap: these fixtures were typically located at the intersection of 4 cubies.

I issued my own bulletin to all clients: explained the ’non-passive’ to clients, scared them as best I could, and made it perfectly clear that ALL of these fixtures MUST have their Tempered Glass Covers properly installed and secure.

The outer glass may be ONLY 800F degrees, the inner glass typically 2,000F, a failure, up to 2,700F

I never specified them again.

I had metal halide bulbs over s fish tank.  The fixture had a safety glass.  When a bulb exploded (near its end of life, a common occurrence) a few glass fragments were so hot they fused with the safety glass.  I’ve also had tv projector bulbs explode (also metal halide).  As I explained above, failure from skin oil happens with such bulbs because the oil carbonizes from the heat, turns black, and the black absorbs the high intensity light instead of letting the light pass through, and it is this additional heating from absorbing the light that causes failure.  Even if a carbonized black spot did develop on a tube, it doesn’t give off enough light to cause overheating; the tube will NEVER fail this way.  I’ve seen tubes marked by permanent markers; there is no harm from this.

That's also why you're never supposed to touch headlight bulbs when you are installing them.

It’s not recommended to use skin on tubes it hurts transients! Hahah

I heard that licking the tubes will give you deeper sound stage, and better channel separation!

but you can only lick them counterclockwise