Problem without crumbtray : help?


I would like to engrave the back of a mirror (like those photos)

The mirror is hot glued with the frame. My first idea was to unseal mirror with hot air gun but this process breaks the mirror 2 times out of 3 so it’s not a great idea.

My second idea : keep the frame and engrave the mirror’s back without crumbtray (with crumbtray, the frame is too high and but up the carriage). But with this solution, no possibility to have the mirror surface in the good engraving range like in this plan:

So, I’m out of idea. Do you see any other solution? If I try to engrave the mirror in this wrong range, what would be the result?

Thanks for any help an have a good day.


What you’re describing will work. If you know exactly how high your spacer needs to be there are lots of ways to make them with your Glowforge. A box that is that tall works, but even a simple “X” where you make two strips of material with slots in the middle would do it.

That being said if you’re sure it’s hot glue and not a silicone caulk, rubbing alcohol causes hot glue to unstick from lots of surfaces you don’t need much, just get it on the joint and it should work its way into the joint. After a few seconds of letting the alcohol work try to pull the mirror off the glue and it ought to be easy.

Of course you might want to test what alcohol will do to the finish of your frame first… and any other considerations that you might have.

But yeah I’d probably build a spacer.


Thanks, I will give a try to the alcohol. Il will be the easiest way if it works. I could engrave directly on the tray.

With a spacer, I don’t see how to do because to put the mirror into the engraving zone (between 1.5 to 1.9in from the glowforge floor), the frame will still touch the carriage. I maybe don’t have been very clear. I don’t try to engrave the mirror but it’s back (black on the second photo).

So I will first try the alcohol.

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Ah right I misread your diagram. If your tray walls are over ,5” tall you can’t engrave in focus.

Defocused engraves are a thing and have their place but they’re by definition not as crisp, and get less so the further your surface is from the focus point.

You might get an ok result depending on your design but you’d have to try it. I agree that removing the mirror is probably your best chance for success.


If it is put together with hot glue if you preheat the oven to 200 and then turn it off and put the mirror on a support the frame might get soft and fall away from the mirror.


Or maybe not preheat – seems less likely to break the mirror if it’s heated gradually. I’d stick the mirror in the unheated oven and let it preheat, too. :slight_smile:

No heat needed really. The alcohol trick is astoundingly effective. Try it, it’s like magic.


Not my video, but nice demo.


Wow, it’s not even 8am (here) and I’ve already learned something new today. I’m going to have to try this!


Yeah it’s really useful. You need almost no alcohol, too… it almost works like a catalyst, a little alcohol goes a long way as it wicks up into the joint.

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I’ve had my glue gun sticking into a drinking glass until I finally get around to making a stand for it, and the glass has glue drips all over it now. This could potentially offer me several hours of entertainment while I’m stuck in bed – thanks!!! :wink:

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Drink alcohol. Problem solved?


My alcohol-free upbringing has effectively eliminated that option for me–it’s apparently a taste one has to develop when young. It all tastes like rubbing alcohol to me.

I spent a month in Denmark on business one time, and had to drink wine with every meal so as not to be impolite. No matter how I tried (nor how expensive the wine) I just couldn’t taste anything but rubbing alcohol. :stuck_out_tongue_winking_eye:

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I’m not a big wine fan.

But, from what I understand from people I know in the industry, is to largely ignore the price tag - $100/bottle is not necessarily better or more preferred than a $20/bottle.

Not that it matters to you :slight_smile:


So I have tried alcohol method and it works. Not as easy as in the video and the paint on frame is gone too ;)… But that’s not a big problem.

My test was with simple ethylic alcool (90° a ver big dose during 15min) so I should find isopropyl alcohol to see the difference.

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I use alcohol hand sanitizer in a wide variety of applications so would be my go to here. Isopropyl has been said here does bad things to acrylic.

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