umbilical through the passthrough slot and a shroud over the tube?
Interesting. I naively thought that CO2 lasers just contained CO2.
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If you think this discussion is funny, you should see some of the lighting/color science mailing lists (where multiple people break out spectrometers, argue over the readings, build new test equipment to prove a point, etc.).
Gaffers tape blocks small lights pretty well.
But a focused fiber optic probe would pick up light from the tube and surrounding lights would have negligible contribution.
The glow looks a bit ultra-violet ish. I hope that doesn’t age the plastic casing. Fluorescent lights turn ABS yellow very quickly if they are in close proximity.
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I’m not sure that blocking those lights would be a good idea, given the fact that the Glowforge uses two cameras that depend on visible light during operation.
You certainly wouldn’t want to during a normal operation, but just to determine what a spectrometer sees in that pretty pink/violet emission in the tube.
Some pretty crafty bastage around here!
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The light from nitrogen contains a lot of UV – in fact there are instructions all around the web on how to make nitrogen UV lasers using just air for the gas. Warning: be careful, most of those designs are not very safe. And you MUST wear eye protection with UV sources if you intend to use your eyes again in the future. 
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So is it safe to look at the glow of a CO2 laser through glass?
Glass (and most plastics) blocks most UV.
The visible light from the laser tube isn’t a problem.
And the laser wavelength for the Glowforge is deep IR (aka radiant heat) - but as long as it isn’t focused that isn’t much of a problem, and all the focusing in the laser tube is in the direction of the beam.
With a UV laser, even a small amount of transmission could cause problems, and the lens of your eye is sensitive to UV (forming cataracts) – so you want extra protection. (which sort-of explains my collection of OD 7-9 goggles for different types of lasers)
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Yes - it is blocked by two layers of glass, a layer of coolant, and the lid for good measure. 
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Does anyone else think it’s weird that Dan has been answering questions during working hours. My understanding of the world must need a reset.
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While true in this case - but not for this reason - it’s not really technically correct. The light you see is generally safe looking at the tube as @Dan noted. But it’s not focus alone that makes laser light dangerous. Your eyeball’s vitreous fluid will boil with unfocused laser light.
Lasers accomplish their magic through the coherence of the beam. A coherent light source has more output power per unit of input power and hence can be focused tighter. There’s little wasted energy or scatter.
A CO2 laser has almost no light component outside the 10600nm wavelength (that’s the coherence). The light you see from a lightbulb is a noisy mess of frequencies with little coherence. That’s why the sun can burn a leaf only within a small range of focus with a magnifying glass but the laser can blind you from a refracted unfocused beam and why there’s a lid safety switch to make sure you don’t operate the laser with the top open.
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Maybe the Glowforge is secretly done and Dan is just using the remaining 5 weeks or so to mess with us.
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I agree, why else would he be here.
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He may have been kicked out of engineering spaces as is sometimes necessary.
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Solo dad this week while my better half is out of town. Puts my schedule sideways.
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“Solo dad” can be rough duty, all a matter of perspective.
But it has been maybe 2 months since I noticed the time stamp on your forum posts switched from the wee hours of the morning to the afternoon.
I took that as a reflection of diminishing pressure on your time and psyche… meaning things were going well!
After the production circus you have been riding herd on, the kids should be a nice break.
More likely to take a vacation before the onslaught of questions come ship time.
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I think he saves those special nighttime forum visits for the super-secret beta-only forum. Those lucky folks!
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