Top Down Engrave?

Is it possible to engrave top down? I’m starting a business that requires reverse engraves on painted acrylic or glass. The smoke is blowing over the engraved area and discoloring the area that must be clean and clear. I’ve tried to scrub it off or use paint thinner and it won’t clean off. I bought this machine as an investment in starting this business. I sure hope there’s an option that will solve this problem or my business plans will be ruined.

What you need is a mild abrasive. I’ve had good luck with toothpaste and elbow grease, but something made for acrylic would probably be more effective with less effort. :blush:


You’ll find lots of discussion on masking solutions, e.g. Materials Masking Suggestions

You’ll want to use something gentle enough for your paint.

The masking doesn’t help since it engraves bottom up. There is no masking remaining to protect the area already engraved.

Gotcha, I understand. I defer to @geek2nurse!

I have considered that and have found a lot of cases where that would be very useful, however I have also seen that engraving back to front is far more likely to start fires,

If you have good masking the parts the are engraved will collect crud however the parts that are not engraves will remain protected. if at this time you can wipe the engraved areas with a soft cloth damp with Hand sanitizer I think you will find that it will wie up the crud easily and leaving the masking in place till then will protect the paint.

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To answer your question, no. It is a good suggestion to be able to choose which direction. There are pros and cons with the current setup. Many times it has been suggested. It doesn’t seem to be a feature that gets a lot of attention, but when it becomes an issue, it sure is. Hope you can find a solution.

I wouldn’t use alcohol-based hand sanitizer in this case, since alcohol can cause crazing in acrylic.

If it’s the engraved areas that are the problem, and you need them clear (not the white that you get when engraving cast acrylic), you could try this:


Isopropyl Alcohol will cause crazing, I have not found that with the hand sanitizer I use.

4 Likes recommends naptha for removing adhesive & smoke residue from acrylic. It works great for me, just make sure you’re using it in a well ventilated area.

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Based on the physical placement of the air assist fan for this machine, it’s always going to blow the smoke and residue forward.

If you were to engrave from the back to the front, it would still blow the residue forward, but it will build up over a larger area, and as time goes on, it might start to interfere with the engrave depth, making it harder to engrave through the paint. The engrave will be deeper at the back, and shallow at the front.

So that’s a no-go.

Did you try a second high-speed/lower power engrave over the original engrave to burn it off? There would be less residue than the original removal, and it might clean it up.

Make sure you don’t shift either the material on the bed or the image on the screen between passes. Just change the settings in the thumbnail column. And for the acrylic, wait a minute or so between the passes to let it cool.

Second issue…depending on the type of acrylic, the results of an engrave are going to be white. (Cast acrylic.) If you don’t want a cloudy white result in the engrave, be sure you are using extruded acrylic.

There is a way to flood the engraved areas with acrylic solvent to restore the clear areas, but I don’t know what it would do to the paint on the back.

So yeah, you’re going to have some issues to work out. (You’d have some of them with any laser though, and you might be able to do some experimenting to reduce the effect.)

If you just want to take the paint off of the back, run some tests that will enable you to just get through the paint. (Lower power/Higher speed/Lower LPI.) And glass is going to work better for that than acrylic.

Good luck with it.


I don’t want to reply to your other post and reopen an old topic but I had to laugh about your comments about bookmarks - one of my several current methods of keeping track of information is to put it in an email to myself. You do not even want to know how many emails I have… it’s a nightmare. LOL


Would love to know what that is. Every hand sanitizer I have uses alcohol, and causes craze on PG acrylic (even the non-engraved surface).

I believe they all do, but before I knew there might be a problem I was soaking them in Purell and have not seen any crazing. :upside_down_face:

While not many are common there are a great number of possible alcohols.

Interesting. I have Purell, Germ-X, Equate, Amazon (Solimo). They all use Ethyl Alcohol. Germ-X and Equate have 63%, Purell and Amazon have 70%.

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It would be that other 30ish percent that are the real issue. I would experiment with a bit of Everclear, and Isopropyl and see if they treat acrylic differently. the Purell has stuff to save hands or more likely stays away from harsh chemicals that would hurt them.

I was thinking that as I was reading down through the thread. A second cleanup pass. Kind of like roughing and finishing. It seem logical to me…


The Glowforge will probably never have a top-down engrave option, unfortunately.

If the masking is plastic, replace it with paper. The remaining residue will be much easier to deal with.

You can also do a second engrave pass at very low power to clean things up. I have had some success with this on the 2-color plastics, where you engrave away a dark top layer to reveal white.

Get some Novus #1 and Novus #2 plastic cleaners. Use #2 (a mild abrasive) in the engraved areas and #1 (no abrasive) as a cleaner and polish for the shiny parts.


@mpriley1138 It looks like you’ve received quite a few suggestions from our community. I’ll be moving this to Beyond the Manual so the discussion can continue.


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