Octopus Handle Cast

Preface

In my previous clay modeling project, I molded a door handle designed for a double cabinet storage. The vision behind my intricate design is that with two models it would appear to be an octopus trying to escape from the cabinet doors, but only the tentacles are visible to the user. For the clay model, I only designed one prototype with four tentacles with the idea that when I create my silicone mold, I could cast two models where one will be reflected to create the illusion that there are, in fact, eight tentacles.

Molding Phase

The most difficult part of this project was figuring out where my parting line would be for this two part mold. In most of the clay projects, you could simply split the part in half, however, with so many intertwining tentacles at different elevations, that method would no be possible, if I wanted to be able to get my clay model out of the mold. I decided that the best approach would be to have my parting line follow the clay model along the tentacles by splitting each of them in half.

To start the bottom mold, I cut a foam core base that had at least ¾" of clearance on all sides of the clay model. Then, I started building up a ½" layer of paper clay, so that I could have cut a pour hole at the bottom of the base later on.

Once I had a thick enough layer on the bottom of the base, I placed the clay model in the center of the base and then started adding mounds of clay where needed in order to make contact with the elevated tentacles.

As I met the bottom surface of the tentacles, I tried to create a flat surface of paper clay next to my clay model, so my two part mold seam line would be as clean as possible. After all

The most difficult part of adding the paper clay was the two leftmost tentacles because they are touching and very elevated in comparison to the other two tentacles. I had to be very careful in adding clay in these tight crevices. However, after I had cleaned up the paper clay surfaces and built up enough clay to the highest tentacle, I added registration marks so the two parts of the mold would be easy to tear apart later. Next, I cut up sheets of foam core to create a sealed box where the silicone mix would not be able to escape out of the side or bottom. To ensure that the box was secure, I added multiple layers of hot glue around the edges.

Next, I sprayed the interior of the box with mold release spray as depicted below. This addition allows for the silicone mold to peel off seamlessly after it is done solidifying.

After, I began to stir together Part A and Part B of the silicone mix at a 10:1 ratio until they were thoroughly blended. In this first pour I needed approximately 5500 grams of the mix to fill the box at least ¾" past the highest point of my clay model.

After removing the foam core walls, I had to dig out the paper clay to reveal the clay model underneath in order to make the second part of the silicone mold. Unfortunately, the paper clay was sticking to the clay model a lot so I had to use tools to scoop out the clay that wasn't budging. In the end, some of the stubborn pieces of clay were smoothed onto my original clay model as a means of not ruining my original model's smooth surface finish.

After all of the clay was removed or smoothed over, I built new walls to pour the second half of my silicone mold in. However, the walls were not completely sealed so the silicone mix began to seep out of the sides of the walls.

Once the spilled mess solidified, I added new walls and poured the mix once more ensuring that the sides were completely sealed. After that had solidified, I opened the two parts of the mold to unveil that my clay mold was falling apart. The suckers had stuck to the silicone mold, as well, so I had to dig out so that the cavities would remain on my final part.

Casting Phase

With the most time consuming phase behind me, I finally was able to start casting. I cut a pour hole at the top of the mold large enough to fit the spout of the funnel. After, I drilled air holes at the highest elevation of each tentacle to make sure that the resin would reach those areas. I wrapped rubber bands around the silicone mold so they would be held tightly together. I mixed Part A and Part B of the resin at a 1:1 ratio thoroughly and then poured at the top.

Preliminary Casts

Overall, the first cast was a success because it came out of the mold fairly easily despite the intricate intertwining of the tentacles. The only concerns were the remaining clay pieces from the clay model that were embedded in the resin cast, as well as, the air bubbles that were present. Additionally, some of the suckers did not come out completely through the cast. The silicone mold had a bit of residue left over so I used acetone to clean the surface before casting again.

In my second cast, I decided to pour half of the mix and then tilt the silicone mold a little before pouring the remaining mix so that I could ensure that the resin got to all of the tight areas. The second cast filled some more of the problem areas from before, however, the base had noticeable air bubbles.

Final Cast + Sanding

In my final cast, I drilled more holes to improve the air bubble situation. In this last cast, I was able to use the pressure chamber to ensure that the air bubbles were efficiently filled.

Once the cast solidified, the air bubbles were sufficiently filled for the most part except for the base. Seeing that this was the best cast, I decided to sand down this piece for the best finish. Using the dremel, I sanded down all of the corners so that there were smooth transitions between tentacles that were touching. Then, I used 60 and 220 grit sandpaper to touchup the rough surfaces.