How to identify materials?

[Anders Troberg]

I thought I'd take the opportunity of an empty forum to create a reference thread for identifying materials. This is mostly for plastic, since some are very dangerous to cut, but look very much the same, but feel free to add your knowledge.

Perhaps at some point, we can construct a new "safe/unsafe to laser" list, which includes this info.

So, if I find a random bit of material in my shed, how do I identify it?

(Edit: I think we can assume that people can identify basic "groups", such as plastics, metal, glass and wood. What I'm asking for is more precise identifications ("What kind of plastic is this random bit from a sign?" type of questions).)

[Gene Uselman]

That is an excellent question. I will be rebuilding the FAQ section and this one thing that need to be addressed. I will move this to the FAQ and we can build upon it. Gene

[Jesus Lau]

Hi,

I've had found this article on Hack-A-Day a while ago, I didn't had a laser back then, but now that I have one, I hadn't have the time to use it in practice.

As I've read almost the entire feedback in that post comments section (and you should do too), some users have posted some interesting aspects of plastic identifying using this method.

[Scott Miller1]

Well, one lesson I've learned the hard way is to write the material on a label as soon as I get it out of the box! I've got stacks of material around the shop that I thought at the time I certainly wouldn't forget about, and of course I did.

For mystery plastics, I mostly rely on burning things. I'll shave a curl off with a knife and light it. How it shaves helps identify it, too, but mostly I'm paying attention to how it burns and the smell. You can get plastic ID kits with samples to burn for comparison. For me, ABS is the easiest smell to identify - it instantly takes me back to my barn workshop as a kid, accidentally melting the heck out of Radio Shack project enclosures with my soldering iron.

PVC you should probably learn to identify by feel, rather than huffing the fumes.

[Gene Uselman]

Well, one lesson I've learned the hard way is to write the material on a label as soon as I get it out of the box! I've got stacks of material around the shop that I thought at the time I certainly wouldn't forget about, and of course I did.

I can identify with that... I have printed labels for every thinkness and all the laserable materials[we have a sign shop so it is easy for me]
but a lot of materials are hard to tell apart. We use a lot of poly-carbonate as well as acrylics. Polycarb does not laser well as it burns easily, a shaving will emit black smoke BTW. We also use a fair amount of expanded PVC sheet for cheap signage and that is usually fairly easy to recognize and should never be burned/lasered of course. I plan to check into the plastic ID samples... a great idea.