On Wednesday, January 18, 2017 at 6:55:28 PM UTC-5, Tim Wescott wrote:
On Wed, 18 Jan 2017 15:28:30 -0400, Leon Fisk wrote:

On Wed, 18 Jan 2017 13:02:13 -0600 Tim Wescott
wrote:

snip
Polystyrene putty with chopped fibers in it works quite well both as a
putty and as a glue for polystyrene parts. My dad's shop used to have
the local Glidden supplier custom-mix such putty. It was excellent
stuff. (May still be -- I don't know what the company uses now).

It won't necessarily stick well to metal, though. I'm not sure what
body fillers like Bondo use to increase the bond.

I found several youtube videos showing how to use acetone and
"styrofoam" packing material to make some:

https://www.youtube.com/watch?v=6E8bu2wLYGU

I'll have to remember that. Usually have some of both around. Looks like
it could be really useful stuff for making repairs...

Blech. I said polystyrene, meant polyester.

Bondo is usually polyester, which is a catalyzed material and far
superior to polystyrene. Bondo, for instance, should not melt if you dip
it in acetone.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

I'm looking for work -- see my website!

Yeah, the original was just polyester resin and talc. They include some lighter fillers now, and they have enhanced adhesion to steel, galvanized, etc..

Polyester resin in general is a very poor adhesive. Even in exterior home repairs, repairing dents in siding and rotted window sills, there is a trend among the pros to use one or another of some lightweight epoxy resins today.

However, they typically cost at least twice as much; they have a narrower range of application temperatures; and they take much longer to fully harden..

I just used a couple of cans of Bondo to repair the 92-year-old clapboard siding on my house. I was using it down to 40 deg. F, and it hardened in minutes. Used right, it's terrific stuff. Just don't count on it getting good adhesion in thin layers. It needs some mechanical grip.

--
Ed Huntress