Silly Putty for molds- it kinda works!

Andrew Gorman · Post by **Andrew Gorman** » Sun Apr 17, 2005 3:37 pm

Hi folks.
I needed two of a particular bomb shape, but only had three halves... I think the other half ended up as a fairing of some kind, or it might be in a motel carpet somewhere. So rather than tryining to remember what kit from Big Lots the bomb came from, I tried molding a copy in epoxy glue with Silly Putty as the mold material. It was available, and seemed like it would work. The first attempt was not a success, since the silly putty sagged over the curing time. I ended up with a wide, flat, bomb half. What I needed was a shell around the silly putty to keep it from creeping too quickly. I crammed silly putty into a drop tank half slightly bigger than the bomb in question, pressed it over the bomb half and trimmed away the excess silly putty. The bomb half popped right out, and I filled the cavity with 15 minute epoxy (all I had around). After curing overnight, I had a usable copy of the missing bomb half. Cheap, quick, and easy. I should have stuck some bits of sprue into the back of the curing epoxy to make some keys for when I finally glue the halves together, but what I have will do just fine. No epoxy stuck to the silly putty. The main drawback is that the SP mold will sag and creep, but having only a thin layer of putty inside a rigid shell, and using a quick setting resin should eliminate most of these problems. Hope someone finds this useful,
Andrew

Lt. Z0mBe · Post by **Lt. Z0mBe** » Mon Apr 18, 2005 11:29 am

I've done a similar thing before using Silly Putty. I built a little Lego box around it, and crammed as much putty into it as possible to make sure there was absolutely not air pockets inside the box. Next I pressed the part into the putty. The master was a Mk. 82 bomb half whose fins I'd sheared off, by the way. I "poured" in CA glue, and then I did another with some epoxy. Both worked pretty well.

Z0mBe

Shinnentai · Post by **Shinnentai** » Mon Apr 18, 2005 11:13 pm

I've played around with this too for duplicating greeblie bits. I use a little metal sauce dish (about the volume of a shot glass) from Target as an all-purpose mother mold for the silly putty.

Try using five minute epoxy for the casting- it doesn't give the putty enough time to sag before the part has solidified.

I tried using super glue at one point, but it bonded to the silly putty.