J-B Weld for casting

TREKKRIFFIC · Post by **TREKKRIFFIC** » Fri Sep 26, 2008 1:48 pm

Does anyone remember a post about a guy who used J-B Weld to make molds for casting small resin parts ? I'm looking for an easy way to cast three small 3/32" diameter clear resin globes for spacemen helmets; I'd rather not have to use liquid latex for something so small if there's an easier way. I was thinking of taking a metal bead of the right size and pressing it into J-B Weld down far enough to leave a tiny opening where the neck would be. I'd need to split the mold to remove the bead, then hang the spaceman figure head down into the cavity and pour the clear resin around the head. Hopefully, when cured I'd have a N scale spaceman in a clear round helmet. If anyone has worked with this stuff I would like to confirm how easy it is to peel away from the resin. Would I need a release agent of some kind ? Any tips or comments would be appreciated as I haven't done much casting until now.

Joseph Osborn · Post by **Joseph Osborn** » Fri Sep 26, 2008 10:13 pm

Sounds like a job for PVA. Without some type of release, the JB-Weld epoxy will bond to the bead, and the clear resin will bond to the JB-Weld epoxy. You have to think of it in terms of rigid fiberglass casting, so you look to the materials used in that discipline. Hope this helps!

Post by **TER-OR** » Fri Sep 26, 2008 11:00 pm

You can thermoform with blister-pack plastic too. This will give a very thin piece you can use as a visor. Heat the blister pack plastic over a light bulb or candle, then pull it down over the piece. I've replaced canopies like this.

Joseph Osborn · Post by **Joseph Osborn** » Fri Sep 26, 2008 11:27 pm

Terry, I think he's looking to make some 50's-style bubble helmets, kind of like this:
http://www.beinghave.com/Stewarts/Great ... aceman.jpg
except round, of course.

belkin321 · Post by **belkin321** » Sat Sep 27, 2008 12:54 am

Get a 5mm or 10mm white clear LED if that is about the size helmet you need, and carefully remove the leads and internal parts. They somewhat look like old sci fi space helmets.

Chacal · Post by **Chacal** » Sat Sep 27, 2008 8:14 am

If you just dip the head in resin, maybe surface tension will make it round enough—in layers you can even use Future. Dip it and hold it upside down until the resin/future cures/dries.

Post by **TER-OR** » Sat Sep 27, 2008 10:26 pm

Ah, that might be tricky.

You can get acrylic spheres and beads at craft and hobby stores. You can also get Knead-a-mold silicon mold material. I have found the best, clearest clear resin commonly available is Envirotex light. It takes two days to fully cure, so you can usually get it to release most bubbles.

If you prep some knead-a-mold by pressing in the sphere, allowing it to cure - 20 min is usually fine, then remove the bead. Then prep some more and press your figure inside, working it around the neck to where you want the dome so the head is in the sphere recess.

Then mix your envirotex - more than you need... Allow it to sit for a while so the bubbles rise to the surface. Gentle mixing during this phase can help. After an hour-ish, gently place drops in the globe recess, using a pin to make sure there are no bubbles around the head.

Practice pieces will probably be required...

Anyway, that's how I'd do it.

Excess envirotex light can be used on wood as a finish, or to make clear windows.

TREKKRIFFIC · Post by **TREKKRIFFIC** » Mon Sep 29, 2008 3:18 pm

Thanks for all the suggestions everyone. This is the type of helmet I'm trying to replicate:

http://farm4.static.flickr.com/3293/289 ... 60fa_o.jpg

These are the N scale figures I'm using:

http://farm4.static.flickr.com/3163/289 ... 952b_o.jpg

I tried using Testors Clear Parts Cement and it worked well just squeezing a little on the head until it built up into a globe but after it dried the helmet was rather opaque. I want something clearer.
Here are the spacemen afetr using the Clear Parts Cement:
http://i146.photobucket.com/albums/r259 ... G_0933.jpg

I have this casting resin:
http://farm4.static.flickr.com/3012/289 ... b433_o.jpg

If the Clear-Lite has viscosity similar to the Testors I should be able to use the same technique. Guess I could always test it out on some piece of scrap first.

Post by **TER-OR** » Mon Sep 29, 2008 9:05 pm

you should be able to get that to work. You'll need to figure out how thick it needs to be before you apply it - so it can hold a globe shape.

I'll be interested to know how this works.