Making an Aluminum Plaque
I made this plaque for my mom for Christmas. But making a plaque this way isn't easy. It involves carving the plaque out of plaster, making a mold, and then casting the plaque with aluminum. However, they always turn out great!
The first step was to get obtain the outlines of the animals I wanted to include on the plaque. I used Solidworks to trace around the pictures I wanted to use, and then I printed out the outlines.
The next step was to cast the plaster. I found a box that was approximately the right size, mixed some plaster and water up, poured it in, and then let it cure.
I then took the block of plaster out, and started to smooth out one of the sides. Unfortunately, I pushed too hard at one point and broke a significant portion off of the plaster. Even though I broke off a significant piece, I still had enough to work with. I also traced the cut out pattern onto the block of plaster.
First, let me show you the tools I used to carve the plaster. To do delicate work, I used this yellow handled tool. It has two ends, which allow me to use whichever suits my purpose at the moment. For rough removal of plaster, I use a pocket knife. It works surprisingly well, although I am sure there are better tools out there that I could use.
I started the carving by scribing a line around the outside of each of the profiles. I made it somewhat far away from the line so that I didn't make a mistake. I then started to deepen and widen the cut until I got closer to the line. During all of this I made sure that I held my tool at an angle so that each profile had a draft to it. This helped with removing the mold from the pattern later. One important thing I should probably mention is to keep the plaster block in a sealed plastic bag when you aren't working on it. It needs to be damp in order to carve well. Once it drys, it is much more difficult to work on it.
I then worked on rounding out the plaque's shape. I used my Shinto rasp for this, although I think I could have come up with a better way to do it. The rasp kept getting clogged up with plaster, which greatly slowed my progress.
My next step was to remove all of the excess plaster so only the profiles would be sticking up. Like I mentioned earlier, I used a pocket knife for this.
After I removed all the plaster I could or wanted to, I let the plaster dry. I then sanded it down until I was satisfied with the surface finish. This picture doesn't show it completely sanded, but it is mostly done.
The next step was to make a mold and cast it. Unlike most of the other molds I make, this one was only a one sided mold. I put the pattern down with the carving facing up, and then packed molding sand (petrobond) on top of it. I then picked the mold up, and flipped it over. Because the plaster was so heavy, it just stayed put on the floor. Unfortunately, the plaster pattern broke! That meant I only had one chance at casting the plaque. Luckily the mold turned out well.
I then took the mold outside and casted it in freezing cold weather. The casting turned out okay, but the aluminum contained more slag than usual, and some of that got into the casting. This resulted in the casting having small holes on the face.
Because I didn't like the way the defects looked in the final casting, I did something I had never done before. I filled the holes with some auto body filler, and then I painted over top of the profiles. It might not have been what I originally pictured in my mind, but I was happy with the way it turned out.
Thanks for reading this article. I hope you enjoyed it!