My lid gave up the fight.
I’ve read all of the existing posts on here regarding recommendations/fixes, but would love to hear from people who have completed the regluing with what they used, how long its been, if it was successful, and if they would do something different. Would be nice to have all that info in on centralized thread.
Im planning on attempting the reglue soon
Jonathan Gleich gave me this advice:
Mix epoxy
Use popsicle stick smear it on both glass and metal hinge
Put plastic bag below to catch drips
Close / align lid
Put 1 gallon plastic water bottles / phone books over area
NO GLASS NO METAL NO CERAMIC
Let cure 24 hrs
Single edge razor to remove excess
DONE!
I haven’t tested it (never needed to) but he’s done lots of glowforge repairs.
What does this bit mean, for the weights?
I think he’s saying to weigh it down with something that isn’t likely to crack the glass.
The lid is tempered glass. Anything that might even scratch the surface is risky – there’s a lot of tension in the glass, if you break the surface the entire panel can “explode”, meaning crack into a ton of small pieces like automobile glass.
There’s a particularly nasty way to break a car window with something called a “ninja rock”, basically a smashed piece of ceramic (traditionally made from a broken spark plug). You take one of those little shards and fling it at a car window and the window shatters.
So yeah if you put something rough on the surface of the glass and nick it you might have larger problems than the glue.
No experience, but sorry to hear about your lid. Mine feels “stiff”. I am always wondering if it’s getting close to detaching.
I just saw this the other day on a Mark Rober Video.
I’m always paranoid about glass, but tempered glass isn’t THAT delicate. It’s used for coffee tables, shelves, and pinball machines, which get a lot of wear and can have direct contact with other glass items.
It’s a matter of relative hardness, like @evansd2 noted. I seem to remember someone here dropped a ceramic magnet from a short distance and shattered the lid.
takitus!! Good to see you!
Too bad about that, but your machine still works? I’ve not had to do that repair, but in my 68 years the best adhesive I’ve ever seen is PC-7.
eh you too man! hope youre well! thanks for the recommendation!
You can smash the head of the drop with a sledgehammer and only put a dent in the sledgehammer but break a bit of the tail and the whole thing explodes. That is because the glass expands and shrinks with temperature but unlike metals will never bend.
I have actually seen glass being tempered. First, you heat the glass to a point that stress can be relieved, a couple of degrees too much and it will sag. Then, when the glass is at that perfect temperature you blast both sides with very cold air. When you do that the outermost layer shrinks and the layer just inside gives a bit to allow it. As long as there is an even gradient everything is fine. The glass towards the outside keeps shrinking as does each slight step inside and the step still hot in the middle gives way. This gets to be an issue as the center is reached and there is nothing left to give. So the forces of compression get bigger and bigger with no place left to go. So where there are big forces like a 50-pound weight in your lid the physics does not create give on the bottom but some of the stress on the top is relieved. This is like stretching rubber bands. Once they reach their maximums they will take a lot more to pull the last bit than the inch before that.
The weakness comes at sharp corners. You have huge forces perfectly balanced. Break that balance (like say have a fire under one side) and as any bit lets go and releases the force, it unbalances the bit next to it and that releases the forces next to it that lets go, and so on. Thus alerting the person in the next room that they should have been watching.
This is why it resists scratches up to a point as well. The forces pushing the top to be smaller are so strong it even resists the scratch… up to the point the forces are unbalanced 
Fun fact. If you have polarized sunglasses you can see darker spots in tempered glass. Those spots are the arrangement of the nibs that were blowing the cold air and thus are transmitting the light rotated more than the light areas. If the light hitting is polarized you get rainbows.
And today i learned why things look like that.
Corollary fun fact - If you have a light source like a polarized filter turned so it is 90 degrees from your sunglasses, (afternoon sunlight reflecting off the Glowforge lid will do), and you have some clear acrylic shaped as the two designs of earrings that you want to know which is stronger or where the weakest part is you can use the sunglasses to look as you apply pressure and the rainbows will dance most where the strain is the greatest telling you where the first point of breaking will be…
Living hinges work great that way too! Try long ellipses vs rectangles. or several different patterns and you can see which ones will be stronger or weaker.
Keep us updated, mine is letting go too and I’ve been dragging my feet!
Another fun thing is another polarized filter(another set of glasses) 90 degrees and it’ll cut off all light from passing through. Learned that one in high school or middle school science class.
But the real fun is using multiple at multiple angles.
Lots of things are polarized light sources. Polarized sunglasses can block LCD screens, like gas pumps and computer screens. Older iphones were polarized, not sure about new ones. Might get into my classroom supplies and pull out the polarized filters and play around later.
I used to like to disassemble my calculators in high school, flip the polarizer and get an inverted display (white on black). Good times.
Fun rabbit hole for 3d scanning folks
https://www.google.com/search?q=cross+polarized+photogrammetry
Yeah, all true, but as long as you are not striking the lid glass from weird angles or throwing spark plugs at it…
I deal with giant sheets of tempered glass for my pinball games and that community has found that edge strikes are where the real risk is.
People are treating the lid like it’s a bomb but we all deal with tempered glass every day without worry, that’s all I’m sayin’. A little care goes a long way.