10: Molding & Casting

Lab Day 10

In lecture, we learned about molding and casting, as well as wearable textiles. Because neither of these topics were directled related to my final project, I decided to make a mold of a small dog statue/paperweight that I had. To begin, I put clay on the bottom of the dogs feet and then I put it inside of a cup. The shape of the dog was quite convient as I did not have to attach any additional supports because the dog could just rest on its feet.

Next, I created a mixture of two different types of silicon (of about equal parts) in a cup. I used a popsicle stick to stir the mixture. To minimize the bubbles, you should stir the mixture in a figure-eight, moving side-to-side rather than around in a circle. Bubbles are problematic for the rest of the process as they can lead to deformations.

Then, I poured this mixture into the cup with the dog. I pinched the end of the cup to make a funnel spout to make the pouring more controlled. When pouring, it is important, again, to avoid bubbles. Some ways you can do this is by "ribboning" -- or overlaping layers of the mixture in the same part. You should also pour slowly. Finally, you should try to pour around your object rather than on top of it as this will make it harder for bubbles to form underneath surfaces where there is a gap of liquid. I found that it was most difficult for me to pour around the dogs head as it was so close to the end of the cup that there was not a lot of space for the liquid to pour through without touching the head of the dog.

Once I had finished pouring the silicon, the cup looked like this.

Then, I let it sit for a couple of hours. Once the silicon had hardened, I use an x-acto knife to cut a line around all of the sides. I then took the dog out of the mold. Next, I mixed the plaster with water and stirred it in a cup. The texture and consistency of this should be similar to that of yougurt. Because my mold was now in two different pieces, I needed another object to hold it in place. Originally, I was going to use a clamp, but I was worried that it was going to squish the silicon too much. I decided on using a smaller plastic cup (the one that was used as a scoop for the plaster) to hold the mold in place while I poured the plaster. Once I finished pouring the plaster, I put another of the original cup over this contraption and then inverted that cup.

After letting it sit for a couple of hours, I decied to open my mold. When I did, I found that the top of the dog had failed to be replicated in the cement.

We concluded that this most likely occured due to a mixture of factors. Once, I do not think I had enough plaster inside the mold. And two, which is a likely result of that, was that there was a large air bubble at the top.



Since the mold still seemed relatively functional, I decided to reuse the mold and try again. This time, I made sure to tap the container down several times after filling it with the plaster. I found that when I did this, not only did it reduce the air bubbles, but it also revealed that there was more room for plaster to be poured. After doing this the second time this is how the mold turned out!