From the manual, pages 7 and 8 as @eflyguy already pointed out:
Materials Safety
Laser-Compatible Materials
“Laser-compatible” refers to materials that can be safely processed with the CO2 laser in the Glowforge unit. Materials that are not laser-compatible may catch fire, emit hazardous smoke and fumes that cannot be controlled by exhaust or filtration, and are a health hazard to you, your neighbors, and your Glowforge printer. For this reason, you must only put laser-compatible materials in the Glowforge unit.Proofgrade™ materials
Glowforge sells a line of Proofgrade materials that are laser-compatible and give top-quality results when used with the Glowforge printer. To learn more about Proofgrade materials, go to glowforge.com/materials .
Laser-compatible materials from other suppliers
Other suppliers like Inventables.com sell material that they indicate is laser-compatible. If you are uncertain, ask the supplier if the material may be processed safely with a CO2 laser.
I’ll repeat and emphasize because (honestly) reading manuals is hard1:
Materials that are not laser-compatible may catch fire, emit hazardous smoke and fumes that cannot be controlled by exhaust or filtration, and are a health hazard to you, your neighbors,
and your Glowforge printer.
If you are uncertain, ask the supplier if the material may be processed safely with a CO2 laser.
That is a very clear warning.
EDIT: Oh wait, it gets even better!
What if I’m not certain whether my materials are laser-compatible?
If you aren’t completely sure that your material is laser-compatible, do not put it in the Glowforge unit.● Some materials look similar to laser-compatible materials, but are different. For example,
vinyl can be mistaken for some laser-compatible materials but emits harmful smoke and fumes.● Materials may have contaminants, coatings, or additives that are not laser-compatible.
For example, certain plywood glues, inks, adhesives, dyes, and paints may not be
laser-compatible.● Some materials can reflect the laser and damage your Glowforge unit. For example,
copper and chrome can reflect the infrared laser light.
They do specifically call out vinyl, so… like, end of discussion.
There is no such thing as a list of every thing you can possibly put in the Glowforge, it’s unreasonable to think that they could provide a definitive list. Did I think it was a bad look for them not to explicitly tell me if I should engrave a rat skull? No, of course not. I took my time and looked up to see if anyone had engraved bone and used sound judgement.
You don’t like the forum, ok fine, maybe searching the forum isn’t something that everyone can do. So, I decided to try google, and searched for “is pvc safe to laser cut” (provided here for you):
https://www.google.com/search?q=is+pvc+safe+to+laser+cut&oq=is+pvc+safe+to+laser+cut
About 31,400,000 results (0.68 seconds) Thirty one million! Google, ever the helpful beast that likes to scrape content, even makes a nice little result card. Check out what it says:
Although polyvinyl chloride ( PVC ) can in fact be cut with laser , the thermal process produces hydrochloric acid and toxic fumes. For this reason, we advise you not to use laser for cutting PVC in order to prevent corrosion of your laser system and to ensure the safety of the machine operator.
Similar results are found when you ask “are vinyl records safe to laser cut”. The big surprise is that if you ask the same thing about fake leather, the top result for me is completely incorrect. The good news is that the rest of the sixty six million results have lots of posts that get it right, fake leather is often pvc, and pvc will kill your machine.
Glowforge cares very much about customer satisfaction, that much is obvious at every turn in the forum and in their public communications. They don’t want people to break their machines, it is a loser all around – unhappy customers take to self-righteous facebook posts and tweets and even come here and raise a ruckus.
On the other hand, they also can’t anticipate all the crazy things we’ll do, nor can they appear to be providing a canonical list because it’ll give you a false sense of security and possibly open them up to liability.
It’s a laser, burning things. Use your noodle.
1 I mean it, I am sympathetic. Reading manuals is hard when all you want to do is go play with the new laser machine. Yet here we are, it’s a fundamentally dangerous tool on some levels, and so caution is absolutely required. We’re adults, let’s act like adults and try to read the manual first. (he says, having himself barely skimmed the manual before trying the laser)