polystyrene mouldings


CGF, Certified Grumble Framer
Jul 24, 2004
Round Pond, ME
I checked out the threads on poly and MDF (not sure of the difference), but they are quite old.
Has anyone had nay recent experience with EXTRUDED POLYSTYRENE mouldings? What's the best way to join them? What type of saw do you use to cut them?
Poly mouldings cut nicely with a saw blade; the fewer teeth, the better.

A chopper works, and makes cleaner miters, but I suggest making several small 'bites'. If you cut through too much at a time, some of the more-brittle plastics might break.

A manually-cranked sander will easily touch up imperfect miters, but a full-speed electric sander will quickly melt the plastic.

Join on the v-nailer, using cyano-acrylate (super glue). Note that accidental glue on the moulding's finish will ruin it. Ordinary frame glues, made for porous surfaces, will not work on polys.

Due to the density of polystyrene, v-nailing will often cause a gap on the outside of the miter. (MDF mouldings have this same characteristic, to some degree.) This may be avoided by gluing/vicing the corners before v-nailing. Or, if you work with only poly mouldings, slightly changing the miter angle will compensate, but then the angle would be wrong for wood & metal mouldings.

"What would you do if you weren't afraid?"
I'd jump out of an airplane without a parachute. Sometimes fear is a good thing.
A lot of folks simply hate the plastic mouldings as not worthy of our efforts.

We, too, tried these years ago and were underwhelmed with quality and use.

Then a wise old framer named Jim Miller suggested that we give them another look. If it was good enough for Jim, by golly, it certainly would meet our standards.

It most assuredly fits a need and the stuff is just flat out good looking. And when price is important (and it seems like it is more and more often) it sures fits the bill

I hate to comment on framing as I don't do any of it, but every single one of my framers has zero problems. And believe me, if they did, I would know.

They do not do anything extraordinary, no special trick, no special blades-just the glue we get from the vendor

It is now a critical element in our marketing scheme and we sell more and more of it when price becomes an issue.

And if you sell preframed art or mirrors, it is a slam dunk

This ain't your daddy's Polystyrene
gperry: I'm not going to add to the above two pro's comments. However, there was a thread in late October or Early November that covered polystyrenes. MDF (Medium Density Fiberboard) is an entirely different animal.