Proofgrade Acrylic Slump Bowls



That’s quite a clever setup with the bowls, and the final result is quite pretty. I look forward to getting my GF so I can try something similar.

I’ve been working with acrylics for many years, and I would like to caution you on using your kitchen oven (or anything else you would use to cook food) to do your heat bending. Acrylic has a very small temperature range between being pliable enough to bend and beginning to decompose. It also releases chemicals as it melts, and should always be heat formed in a well ventilated area. Acrylic can also catch fire just outside it’s bending range and is quite toxic when burned.


I’d love to try this with a record!


Vinyl, bad idea. We periodically get reminders from each other that burning vinyl is both toxic (bad for you) and corrosive (bad for your Glowforge). Maybe if you laser cut a pattern for cutting with more conventional tools. From there, I would be curious if a heat gun, outside or well ventilated, would be safe.


Thank you for the heads up! Cutting the pattern would be a good idea. I’ve
used a heat gun on vinyl before (outside). Getting it pliable isn’t easy
because it cools so quickly which is why I thought cutting it would work
ok. I didn’t know it was corrosive though. Thank you!

Elizabeth Davis
Wadsworth Middle School
7th Grade Computer Technology


I didn’t know until I learned it here. I guess it is the case no matter how it is burned, but it is especially bad with a laser cutter because you can destroy yourself (toxic fumes) and your laser. It apparently requires a very specially designed laser to laser cut vinyl. As awesome as Glowforge is, that wasn’t part of their intent from the beginning.


In its common usage Vinyl, as in referring to phonograph records, refers to PVC, Poly(vinyl choride). So if you see something called vinyl it’s PVC.

But other materials may have vinyl in their name and be fine to use. The vinyl monomer is not the problem, it’s what gets attached to the vinyl monomer that is the problem. Vinyl is pretty simple, just some Carbon and Hydrogen. It’s the R in R−CH=CH2 that’s needs to be worried about.

White glue is PVAc which is Poly(Vinyl Acetate) which is fine to laser.
PVAl, Poly(Vinyl Alcohol) is also fine.
(Note that sometimes just PVA is used to denote the two above, so be aware.)

Henryhbk uses PVAl in some of his projects.

As jrnelson pointed out, it’s when the R is a halogen (e.g. fluorine, chlorine, bromine) that problems occur.

Bottom line:

If the material’s name is vinyl immediately think danger. But if part of its name is vinyl assume the worse, but hit Wikipedia to see if it’s halogenated.


Yeah, I was thinking of that post, but I forgot where it was. I haven’t bookmarked all the ones I want for reference, yet.


Chlorine gas. Don’t even think about it.


sort of, the real concern is that it immediately takes on water from the air to form HCl and HClO (which pretty quickly converts to HCl and O2).


Nice work! That looks great I think :slight_smile:


But in our context it’s more damaging to the machine than to people. It takes a fair amount to hurt you and in concentrated form - the stuff produced by a laser is headed out the exhaust where it will be rapidly dispersed into a cloud of good air. That’s not to say you want to be sticking your head in your laser and doing deep breathing exercises :slight_smile:

The real issue is the damage it does to electronics. It’s highly corrosive. Really highly corrosive. In mist form it gets everywhere and will eat a laser in a matter of days. It looks like it’s been in the ocean for decades or like it rotted out. Just amazing when you see what it will do.


yes because in our context it immediately forms HCl


Actually remember your stomach is full of very high molar HCl. Every time you belch or have heartburn/reflux that is the HCl coming up your esophagus (and you typically breathe a reasonable amount in - it’s OK you are designed for this, we all do it every night while asleep). We will often see pH around 1.5 in gastric contents (takes a lot of burning to reduce that Shake Shack burger!).

We (mammals) actually count on the super low pH to keep up safe from bacteria, as without it - omeprazole I am looking at you - you aspirate bacteria laden oral contents at night; this is why long term use of proton-pump inhibitors in the elderly increase the risk of aspiration pneumonia. You’d have to generate a lot of HCl gas to be a problem for you nearby, not saying HCl is good for you and Cl gas is way worse as it forms all sorts of nasty compounds in you including HCl inside cells, but unless you are massively cutting chlorine laden stuff with your head in the output vent, much more likely you would destroy your device first (which would harm badly you by GWS - GlowForge Withdrawal Syndrome)…


I should add, your eyes on the other hand do not like acidic fumes… As anyone near a pool knows, or sometimes you note some eye burning after a particularly large belch… Far more dangerous at even lower levels to your eyes, and that damage can be permanent - so always have full eye protection when working with acids.


Great work. Thanks for such good step by step


Is it possible to use a heat gun in place of an oven to warm the acrylic? I assume that would be a lot more difficult but could bypass the issue of doing this in your home kitchen with a chance of fire/fumes.


I didn’t try it since the comments about using a heat gun talked about how hard it was to do.

One off bowls for proof of concept doesn’t concern me too much. I wouldn’t do a production run.

I have an old oven at my farm that would work perfect for this. It’s small and I don’t use it any more. If I decide to make more, I have that.


Don’t think so. I couldn’t get the whole piece to reach & hold the temperature needed. I didn’t want to use the kitchen oven so I went with my gas grill. Worked fine - just watch your temps.


It could possibly work to make a more “abstract” bowl? (Haven’t tried but imagine would cause more of an uneven “slump”)


heat guns can work, but they take a lot of time. The ideal if you want to use a heat gun is that your molding surface is metal, and you aim the heat gun at the metal instead of the acrylic.

If you have enough spare metal laying around to build your own enclosure around the acrylic and whatever you slump against, you can build a pseudo-oven wherever you want.

Or if you go to a local appliance store, they quite likely do installations and offer free removal of the old appliance. Then probably store those old appliances in the back of the building until they have enough to load a truck for a run to the landfill. Ask for an old oven, and you probably get it for free.