1/8" thick mirrored acrylic... how to not burn the backing mirror?

high all… I’m to cutting 1/8" thick mirrored acrylic. I’ve used PF medium acrylic setting and it cuts like a charm, but is burning the mirror backing a bit. I’ve tried a couple other settings and either burns or doesn’t cut all the way through.

anyone with experience cutting mirrored acrylic?


Are you talking about flashback…burning from laser reflections off the crumb tray? If that’s it, I would just mask the backside.


Yeah a picture would be helpful but @sailbyc sounds about right. Masking will help, a sacrificial layer (cardstock, plywood, what have you)underneath will help even more – cut carries a slight fire risk. Stay away from corrugated as an underlayer, you’re asking for fire trouble.

You might also consider tweaking your settings, if you are getting lots of flashback, it’s likely overcutting. Speeding up , reducing power, or both might be in order.

Also, most have had good luck by putting the mirrored surface up, so you’re cutting into the back of the mirror.


I’ve tried the multi different settings. But not masking or turning over the acrylic. I will try those. Here is my result. Best I could get it

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Yeah that looks like flashback all right. Try masking and/or sacrificial layers. You’ll probably get some improvement. Nice little monogram project, it will look great when it’s done.

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ok, thanks I’ve added masking. will also try and turn over. AND, put some draft board under. One of those better work. :slight_smile: will send update


Don’t forget to enter the full height of the materials.

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If you’re flipping:

Unmask the top surface (now your mirror), and be sure to mask the front (now face down). You shouldn’t need masking on the top.

It’ll wreck your draftboard, if you have cheaper/scrappier stuff around I’d use that, but draftboard ought to do it.


This might produce gasps of horror, but has anyone tried glass as a backing layer ?
Still got a couple of weeks to go before I can give Glowfinger a hug, but it doesn’t stop the brain bouncing off the wall !
It would be interesting to see if it reduces the flash back, or makes it infinitely worse.
John :upside_down_face:

I’ve considered it, but don’t have a piece of glass hanging around.

I have a nice big ceramic tile that I’ve been considering too… non-flammable laser absorbent substrates seem like a great backer, as long as it’s thin enough to not push you out of .5" total height.

The benefits of using something like cardstock include price, availability and so thin you can largely ignore them in height calculations. With glass, it’s reusability and presumably a more forgiving power-absorber. Needs some testing though, I await your full report :slight_smile:


masking the mirrored side did it! turning the acrylic over and reflecting the object did not; however, I didn’t mask either side when I did it. thank you!!


Flipping it over only stops the burned look of the flashback. If you look at the edges you will still see little indentation marks where the flashback happened. Masking is a pain but it’s the way to go. No worries of a cardboard fire, no thickness changes to measure/remember to enter from stacking, etc…

TY! Yes the masking worked great.

Very glad that it worked for you. I mask the back of most things just in case. The surface depends on the material.

I have cut a lot of mirrored Plexiglass. I found that a speed of 140 and power set at 85 gives great results. I keep the masking on. I cut with the shiny side up and with the shiny side down without any flashback.


Thank you for the settings!!

What do you use for masking? I have a job coming up where I’ll be using mirrored acrylic and want to minimize issues.

I work on so many 1/8” extruded mirrored acrylic projects and found the following:

• Proofgrade setting any medium colored acrylic. (I’ll use clear for mirror, red for red mirror etc)
• Mask BOTH sides
• Engrave:

(from the back) MAKE SURE YOUR DESIGN IS MIRRORED so the design is correct from the front. Speed 700 / Power 6 / LPI 450
• Cut: proofgrade setting

There will still be some slight burn especially on the cut but the masking both sides is super helpful.

Hope this helps!


I’ll give your settings a try, too, jimml1234!

Hi! I masked the front ONLY. didn’t need to flip over or reverse image. Is did speed 140 and power 85. I selected proof grade medium acrylic, and Voila! perfection. :slight_smile: hope this helps…