Here are two simple tests for determining if leather is either 100% vegetable tanned (safe to laser), or chrome tanned (definitely not safe for you or your machine). I’ve seen this info buried in other threads, but I thought a demo and freestanding post might be appreciated. Also, keep in mind that there are many other kinds of tannage (alum tawed, oil tanned, etc.) that may or may not be either safe or laserable, but the only one you can trust is 100% vegetable tanned, and you should never laser chrome tanned.
Siegal Effect Test
First, here’s the Siegal Effect test, created by Steven Siegel, who inherited his family leather business and went on to get a Master’s degree in physical chemistry. He serves as an expert witness in leather-related cases (and his company, Steve Siegal Leather sells some REALLY nice bookbinding leathers). To test, you just drop a thin strip of your leather into boiling water. If it immediately curls up into a spiral, it’s 100% veg tan. If it doesn’t, there’s some presence of stuff you don’t want to laser.
Ash Test
In the ash test, go to a well-ventilated area and light a small sample of your leather on fire. If it is hard to light and goes out as soon as you remove the match, it’s veg-tan. Its ash is also an indicator–smear the leather ash on a white piece of paper and the ash will show up as black. If the leather smolders and holds an ember, it’s a no-go. If its ash has a greenish color, it’s definitely chrome tanned.
Thank you for taking the time to clearly explain the leather tests (and results we should be looking for). Also, good to see you had a moment pop back in!
I too am searching/waiting for someone to point out a definitive and authoritative reference to harmful effects of lasering chrome-tanned leather on the machine. I’ve actually found claims that the production of chlorine gas/acid is the result of lasering chrome-tanned leather. It’s been a while since my high school chemistry class, but I just don’t remember anything about the ability to turn chrome into chlorine. I’m not sure whether people are confusing chrome and chlorine or whether they are confusing chrome-tanned with faux leather made with PVC, but it just doesn’t seem to make sense.
I wonder if there are chlorinated chemicals used in chrome tanning? Idk, that’s why I’m asking for real data. Yes chrome vapor is super bad to breathe, but I don’t know what it’d do to the machine.
One of the challenges with any tanned leather, veg or otherwise, is that the specific tanning formulas and processes are very closely held secrets. (Almost as secret as my grandmother’s chocolate chip cookie recipe.) Therefore, it really doesn’t seem possible to pin down exactly what chemicals are being used. That being said, I’ve not come across anything that indicates chlorine is used.
I do very much agree that chrome-related gases and vapor would be harmful to humans, but of course that is subject to concentration. I personally believe that venting to the outside with the resulting dispersion lowers any GF-produced hazardous fume concentration to an acceptably safe level, for me. Where I’m less certain is any danger to the GF itself. That’s why I’d like authoritative info on why people declare chrome-tanned leather is “unsafe”.
Totally with you there, though sometimes I consider getting a booster fan set up. The problem is that it’s one of those things where if you find out for sure, its bad news, Metal poisoning is no joke.
A booster fan to keep it in negative pressure even after it’s done cutting would be great.
Of course… if glowforge just gave us a UI button that says “turn on the exhaust fan” then it’d be a moot point.
I haven’t ever seen any and don’t have a problem lasering chrome tanned. But I don’t do a ton because it doesn’t laser as nicely and I don’t like the feel as much as veg tanned.
Thanks! I’ve been so busy with my kid and working from home that I’m not lasering as much as I want, but I’m almost done with a kangaroo-leather front-pocket wallet that is going to be pretty cool. I’ll post it with the pattern I made when I get it stitched up.
