Losing my mind - mirror acrylic flashback

I’ve had my GF for three weeks now and I have done as much research on products to use, power, speed, tips, tricks, asking on fbook groups but I am literally about to lose it. I am working with mirror acrylic and I assume what I attached is flashback. My acrylic is from Craft Closet and Houston Acrylic. I take off the plastic covering per their suggestion and I paper mask front and back. I actually double mask the mirror part and I put mirror down. I have used the medium blue acrylic preset, I then started playing around with the settings and made my speed to 170 and lowered power but then when I lower power (from full power) it doesn’t cut through. I have tried everything that was suggested when I googled the issue and on facebook groups, I further played with the settings and did many test pieces. Instead of masking the mirror, I used dawn soap. I put computer paper underneath. I have contacted both acrylic sellers and asked them what settings to use which was 160-170 full power . I have wasted a LOT of acrylic now and I just cannot get it to work. I know load of GF users that use mirror acrylic and theirs come out fine. What am I doing wrong, and if it isn’t user error, what would be the issue with the GF??

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I could be wrong…and hopefully someone will correct me, but unless mirror comes in cast acrylic, the engraving on what you show in the photos would make me think that it’s extruded and not cast. That plus the statement that it comes masked with plastic is usually a telltale sign. I actually don’t know if being extruded might have something to do with the amount of flashback, either…but engraving looks poor on it. Might be a contributing factor?


It looks to me like a material issue as well. Flashback happens then the heat gets turned about in the crumb tray and leaves that mark on the back. Having something on the back like paper masking normally takes care of that. What I see in your pieces is the heat is damaging the very material itself and short of many passes that do not overheat the material is the only way to go.

If it does not say cast acrylic on the paper masking I would avoid it in general.


It’s very strange, that damage doesn’t look like flashback at all. Especially the green circle. Is there anything else you’re treating or cleaning the pieces with? Alcohol maybe?


I have seen this happen with plastic masked materials. Remove the plastic and re-mask with paper to help prevent it. You can use painter’s tape or get paper masking rolls.
I think the plastic masking gets too hot and pulls away from the cut, but leaves melted plastic across the surface, causing those imperfections.

She mentioned that she did remask it.

Ah, sorry. Missed that.

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i cut lots of mirrored acrylic I take top plastic or masking off rub dawn dishsoap on it and use med red acrylic settings no flashback ever. try it works perfect

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Is that straight out of the laser, or after cleaning - that really looks like alcohol crazing.

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Though I’ve seen many people use the mirror acrylic from the places I bought and theirs look fine so I don’t think its the acrylic

I’d really like to see the answer to what @deirdrebeth asked above…

No idea what alcohol crazing is. So the green ones I had used this masking that apparently is not good for the laser so I switched it out to a painters tape and it no longer leaves a smudged residue. I think that other masking basically melted on top of the acrylic. As for the flashback I THINK I may have found a solution. I have now being doing 170/79 2 passes and it seems to work a lot better. Some of the scoring sometimes is missed so not sure why but I’m getting on a better path

It’s when acrylic forms cracks and haziness like your pictures after being cleaned with alcohol.

Oh interesting. I never use any cleaner on top especially because it’s mirror

Do you use any cleaner at all - or are those pictures straight out of the laser?

Straight out of the laser. I tried to just use a cloth to remove what I thought was residue but yea it was just like burnt stickiness from the tape

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Have you tried using these?

I use them all the time now when cutting pretty much any acrylic to avoid potential flashback (tell tale jagged cuts at the bottom of the acrylic - especially noticeable on 1/4). With the autofocus feature on the GF elevating things with these little doodads has been a godsend. HTH.

The best way to check is to drop a bit of scrap into what you are cleaning with. If it falls apart the solution is affecting it. If it sits in the solution for a day without falling apart the solution is safe.

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