How to determine if plastic "x" is safe to use

There have been numerous posts asking if <insert name here> is safe to use in the GF. Good questions all, and certainly indicates that folks are thinking creatively!

Plastics come in many different formulations, often making it difficult to know whether or not a specific type contains Chlorine – a big no-no. Not only can hydrogen chloride gas do horrendous things to the optics of your shiny new GF, it can be deadly. :dizzy_face:

So, how to be certain that hunk of plastic is safe? George Graves over at Hackaday pulled together a couple of how-tos on this topic: including a pretty good video of the “copper wire” test. Sure, they involve a bit of chemistry, but that’s better than taking a chance with an unknown plastic. On the other hand, fire is fun to play with! :sunglasses:

As suggested elsewhere, Makerspaces are great resources for the budding lasercutter – if a 'space has a laser, the members have probably tested/used just about everything you’re likely to consider. In particular, the ATX Hackerspace in Austin has put together a fantastic use/don’t use list:

Have fun, but stay safe!


Fantastic test!!! Disappointing that moleskins can’t be etched…


Awesome post, thanks for sharing!!! I’m equally sad about moleskines…I suppose I’ll just have to stick with cutting a stencil! Wonder how sandpaper would work as a means of hand etching? lol


I think this is a great topic, and we absolutely need to be very careful about the various pollutants that can result from burning things. There are lots of possible byproducts, and many of them can be stinky or downright harmful As stated the most common one that is really dangerous is Chlorine. At the same time it is worth doing a little calculation of the total possible Chlorine emission from accidentally cutting something made with it. My only goal is to temper fear of the unknown with some basic understanding of the relative danger.

For instance if you were to accidently make a 10" long cut in a 1/4" thick piece of PVC how much Chlorine would be released? (not that any amount should be considered safe)

My best guess looks like this (please check my math!):

  • Cutting kerf of .008"
  • Material thickness .25"
  • Length of cut 10"

So .008 X .25 X 10 = .02 cubic inches or 0.0508 cubic cm of plastic.

EDIT: This is wrong. It should be .33cm3 (thanks @MikeH) . The rest of my calculations were based on this incorrect number, and I have not rerun them, but looking at the numbers I suspect they were WAY off.

@jkopel - I didn’t check the rest of your calcs but 0.02 in3 is 0.33 cm3, not 0.05 cm3. It looks like you multipled 0.02 in3 by 2.54 when the factor should have been (2.54)^3.

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“On the other hand, fire is fun to play with!” Thanks for the laugh haha

Well that’s what I get for doing math early in the morning. :flushed:
Let’s just leave it at Don’t cut plastics containing Chlorine.


I now have an excuse to buy a torch. It’s to keep the children safe honey! Thanks for posting.


By that logic, a flamethrower should be extra safe! :slight_smile:


So, is this a definitive test for laser safe material? I just did the test on a sheet of acrylic? I used a thicker copper wire, but the flame wasn’t green. So good to go?

I ditto that question ^ Is it safe to assume no green flame = safe? Or can it still be unsafe to laser materials even if they do not produce a green flame?

No green flame just means it doesn’t have chlorine in it, it doesn’t speak to other possible bad results like cyanide, formaldehyde etc., or some flammability concerns around things like polystyrene that I have seen mentioned.

I would like to refer everyone back to the List of unsafe materials thread. It has a lot of great information and goes well beyond just the chlorine issue from Vinyl.
And The Safety Thread should be mandatory reading, since it is very likely that pretty much every one of us will find ourselves facing “fire in the hole” at some point, despite our best efforts to avoid it.


I don’t you to go inhaling mad fumes or nothing, but I thought they removed all PVC from moleskin products, they’re big on natural materials n’ stuff and I’ve had a friend engrave their hardback notebooks for me. Also their soft paper back ones are beauuutiful when engraved.

That being said this was over a year ago so things may have changed… but I don’t want you avoiding a potentially lovely item, so thought I’d mention it just in case!


Saw this on the laser cutting Facebook page.
Pretty informative on which plastics are good for each laser application
LaserProcessingGuide_Plastics.pdf (1.7 MB)


That was extremely helpful, thank you very much! I noticed one thing in the tables: although they state that PVC should not be cut (due to HCl), they imply that marking can be done. Would that be due to the lower amount of outgassing from marking vs cutting? Regardless, I don’t think I would try it.

Its bad for the laser casing but people still do it.