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Does anyone know how to bend a polystyrene sheet? Answered

 For my next project, I need to bend a 1cm thick polystyrene sheet. Does anyone know how to do this? (thermal, chemical?...).

Added on May 4th: just to be sure, I'm talking about EPS (expanded polystyrene). The white isolation panels.



Best Answer 8 years ago

Polystyrene will soften under a grill. You may need to mask it in some way -foil wrapped around card? Keep an eye on it though.


I'm not sure I fully understand your remarks about the wrapping. Do you mean protecting the rest of the sheet of being exposed to the radiation of the grill?

Yes. If you wrapped some card in foil, you'd be able to cover most but leave a strip of plastic exposed to the grill. On some kind of baking-sheet, heat it, remove it, fold.
You'll find it easier than a hair-dryer I think.


Ok, thanks. I think the hair dryer is going to take some time as boiling water had little effect. Just have to find a fairly large grill!! The sheet is approximately 80 x 40 x 2 cm and I have to bend it in just one place.

Oh right. If you could find an old toaster you might make something?


Hey, that might work...add wheels to it so that you can control the distance to the sheet and gradually heat a larger stretch. That's an I'ble on itself!
I'll let you know.

I meant to unwrap the wire, string it up in a line or lines.


If you don't mind, I want to pick your brain just a little bit more...
When I was talking about polystyrene, I was talking about EPS (expanded polystyrene, you know the isolation panels). Where you aware of this, because something tells me we were talking about different things. Are we?

Oh, you're not going to bend that. You could only manage a "crispy bit" for your corner.
Cut it and glue it.


I have a similar task, to bend a curve into a 1mm polystyrene shoot of the type plastic kits are made from. Can this also be done with heat ?

you can bend styrene without heating. It breaks because of tension, so either

tape on the outside or some reinforcement glued on will help. Another similar

method is the use of a compression strap. After bending the styrene will need

to be held to its new shape by attaching it some way or you can glue paper to

the inside of the bend.

How big is the sheet ? 

The sheet is 80 x 40 x 2 cm and I have to bend it on one place.

That's a BIG piece of plastic !

TWO cm thick ? You'll struggle there with a traditional bender then. I think you will have to look at ovens instead, something bigger than domestic.

Can't you just weld the pieces together with solvents ? 


It's big indeed! I think I can reduce the size to 1 cm thickness, but still that's fairly thick.
Welding, mm..., maybe, although it's going to be part of a sandwich panel.


8 years ago

Definitely heat. The best way is to use a form to bend the sheet around and very gently add heat and pressure, bending the sheet around the form and then holding it in place until it has cooled.
Polystyrene has a low melt point so you've got to go slow and easy.

I have heard that dunking the sheets in boiling water is a good way to soften them, but that was for sheets much thinner than 1cm.

mm... means you have your doubts?
I quickly tried emtying boiling water of a kettle onto the sheet, but no real effect. Maybe I was to hurried.

A hairdryer probably won't do it. I'd look at a hot air gun for paint stripping, if you are only doing one off, or I would take it to someone with  a proper bender - lots and lots of schools have them - I know my son's has, because I've used it. You'll have to heat 10mm thick stuff VERY carefully and slowly.

A paint stripper sounds good. This "proper" bender is based on some kind of a grill as well?

Hi Bertus,

A grill would suggest it does an area, no, the "bender" is usually a long, nichrome wire, which is heated by electricity. there is a long slit in a fireproof sheet, and the hot wire beneath. You put your bend line over the slit, and turn on the heat.  Too much, and the plastic burns before it is hot through.


With a hair dryer, would that work?

It may, on the hottest setting.  Hair dryers vary so much its difficult to say for certain, but it wouldn't hurt to give it a try.