Is it possible to make a casting of a balloon?

Hobbit 77 · Post by **Hobbit 77** » Wed Mar 14, 2012 11:24 pm

Here's a crazy question. I'm working on a project that requires a large hollow egg shape, about 2 feet tall. I've looked at plastic eggs but they don't quite have the shape I'm looking for. The closest that I've found is an inflated balloon. Would like to try and make a hollow casting of it. If this is even possible. Thought of creating a two part RTV rubber mold of it. Also thought of injecting the balloon with resin and spin and rotate it til it cures. Another idea I had is to to coat the outer portion of the balloon with resin. Thought also of using paper mache to create the shape. Again, not sure if this is even possible to do but if anybody has an idea I would appreciate it.

Hobbit 77

Chacal · Post by **Chacal** » Wed Mar 14, 2012 11:34 pm

I think you may get good results with minimal fuss by using plaster strips (you know, the plaster-suffused gauze strips used by doctors to make a plaster cast for a broken leg or whatever). Resin is likely to degrade the ballon's latex, any pourable mold making medium will just make the balloon float up to the surface, paper mâché could work, but it'd take more time than plaster.

After you've made the plaster shell, you can use it to then make a mold, or finish it to use it as your piece, or coat it with mold release, and then make a resin copy…

Joseph Osborn · Post by **Joseph Osborn** » Thu Mar 15, 2012 12:28 am

I think anything that generates heat (resin, plaster) might prematurely breach the integrity of the balloon's envelope, or in other words, make it pop! FWIW, I made a big piñata in high school using balloons that were papier-mâchéd into strong hollow spheres.

Mad-Modeler · Post by **Mad-Modeler** » Thu Mar 15, 2012 12:35 am

Paper-mache is your best bet here.

Look at those spherical paper-lampshades or similar.

Umi_Ryuzuki · Post by **Umi_Ryuzuki** » Thu Mar 15, 2012 3:52 am

Mad-Modeler wrote:Paper-mache is your best bet here.

Look at those spherical paper-lampshades or similar.

We used to make our own pinata using paper mache' when we were kids.
Blow up a balloon, or a beach ball and cover it with paper mache and let dry.
Decorate as required, fill it up, then beat it with a stick.

Scott Hasty · Post by **Scott Hasty** » Thu Mar 15, 2012 6:53 am

My mom used to make these when we were kids.

And I've made these for special dinners.

They may not meet your exact needs, but it may give you some inspiration!

dizzyfugu · Post by **dizzyfugu** » Thu Mar 15, 2012 10:08 am

Mad-Modeler wrote:Paper-mache is your best bet here.

Look at those spherical paper-lampshades or similar.

And/or use strips from a newspaper, soak them in thin wallpaper glue, and apply the cross-hatch in multiple layers onto the blown balloon.