Help with casting a floating object in a large mold?

[jbswearingen]

I'm looking to cast sweet gum seed pods in a large-ish (5"x6") mold. I did it once before with single blank silicone molds, and the friction between the pods and the sides of the mold kept them from floating. Now I'm trying to figure out how to cast them writ large. Any ideas?

I'll be using my new, untested pressure pot (*giddy school girls dance*). It drops from 50psi to 42psi over the course of 13 hours, so I'm pretty sure it'll work.

I'm thinking about using 1/2" wide strapping tape--stuff the pods into the mold, and then run a lattice-like pattern of tape over the top--just enough to keep the pods in place. Pour the resin over it and cure it. The tape will then get cut on the band saw and turned away on the lathe.

Any thoughts or advice?

 

[plantman]

Brad; I have never tried this myself, but have had others explain the process to me. They pour their mold with about 1/4" of resin and let cure. They then remove the cast from the mould. Next they fill the mould 3/4 of the way from the top. add whatever they are going to fill in with, and replace the first cast on top of it. This keeps the objects from floatilg to the surface. Sounds like it would work OK. I have cast minerals and gemstones in clear acrylic this way before. Jim S

 

[healeydays]

Hi Brad,

I have cast SGP and boy they have a few spikes and voids.

I usually cast them in the round so I use PVC pipe and the best way is the tape over the top, but I also poke a toothpick thru the tape and have it push the floaters of any type down into the resin and take a small piece of tape to hold the top of the toothpick to the tape I poked a hole in. Works very well.

Mike B

 

[jbswearingen]

I'll look into those; the tube trick sounds neat. I plan on grinding most of the spikes off on my belt sander before casting--I'd rather more "web" than space in the final blank.

 

[healeydays]

I do them 2 ways. One is making little blocks by sanding then flat as a cube, the other is cutting them in half on a saw, sand down the rounded side and resin the 2 side together to look like a yo-yo then clip most of the spikes and hand fill the voids with different colors. Very time intensive, but make great looking blanks.

Not the best pix, but all I had here at work...