Rhino Gas Mask: Cold Cast Horn

I've now cast the rhino horn in cold cast aluminum. Below you can compare the model (on the right) with the finished piece (on the left).

Designing a piece of art such as this requires being able to look at the model—here made of an unsightly conglomeration of resin, acrylic sheet, copper wire, metal eyelets, and brads—and see the finished horn, in all its beauty. (You do think it's beautiful, don't you?) That is the wonder of resin casting, and especially cold cast metal casting.

Cold cast is nothing more than mixing a very finely ground metal powder (in this case aluminum) into resin. Once it has hardened, I sand the surface of the casting to reveal the aluminum beginning with 180 grit, and continue with finer grits all the way up to 0000 steel wool.

The final step is polishing the piece with a Dynabrade rotary buffer, using a foam pad and compounding liquid. That final polishing is the key to getting it to shine.

Rhino Gas Mask: Finishing the Horn Model

Continuing work on the horn model, I've added red metal eyelets and a faux pearl at the top. The model is now complete.

Once the horn is cast hollow in cold cast metal I'll drill through the eyelets to create ventilation holes in order to make breathing easier for the wearer.

In preparation for making the silicome rubber mold I've hot glued the model upright on a scrap of Formica®. The popcorn cup will be hot glued down around the horn, and will contain the liquid rubber while it slowly cures. The white plasticene around the base of the model will become a separate rubber plug which will keep in the liquid resin during the rotocasting process.

Rhino Gas Mask: The Horn

This gas mask was begging for a nasal projection, and so I am obliging it by constructing an exhaust vent reminiscent of a rhinoceros horn.

Here is my concept drawing. The challenge was to make it look mechanical and man-made, while still reminding the viewer of something organic.

I started with a cast resin horn that I've been making for a satyr mask to sell on my Etsy store. I added several rings that I cut out of acrylic sheet (secured with brads), and four pieces of copper ground wire.

The horn will be made of cold cast metal. Like many of my resin mask pieces, it needs to be lightweight, and so I'll cast it hollow. That process is called rotocasting, and it involves taking a regular rubber mold (which can be closed up) and pouring a small amount of resin into it. While the urethane resin is still liquid, the mold is rotated in all directions so that the inside of it gets coated with the resin.

I will do this twice to build up the resin thick enough to be sturdy. In the photo above I've coated the model with white resin to smooth out the inner corners, nooks and crannies. This will make a better mold for rotocasting and will result in a stronger part.