I started this project with the intent to create something I was proud of and could keep forever. After thinking about all the different kinds of artifacts I could create to accomplish that goal, I finally decided to cast something out of brass. Last summer I was intrigued by YouTube star Grant Thompson and his mini metal foundry so I decided to build one of my own.
With decent success melting down brass shell casings and casting mini muffin ingots in the past, I decided I wanted to bring the foundry back to life again for this project. This time I would use the lost foam method to cast something more intricate than a muffin shape for my artifact.
The Design Process
I began the iterative design loop with so many different possibilities in mind for this project. Sketching a few shapes I thought would be cool really helped me to think about what shape I wanted to try. I really wanted to cast brass knuckles but after some research discovered they are illegal to own in Colorado so that wasn’t a hood option for a school project. After a little more thought I narrowed it down to a logo made up of a letter or two. Casting a giant brass “R” to resemble my first name would be interesting but I finally concluded to create the CU logo. I knew this was a good choice since I will be able to polish the brass to a shiny gold finish resembling our school colors.
The Casting Process
To create my artifact I recycled about 5 pounds of brass shell casings I collected after a good day of shooting with my roommates. In order to cast the new object I used the lost foam method. This method allows the molten brass to take the shape of any foam object so I ended up cutting out the CU logo using a soldering iron.
The CU foam piece was then placed in a bucket of greensand with two foam risers sticking through the surface of the sand. Creating green sand was a almost a mini project that had to be completed for the success of this one. Greensand is just a mixture of fine sand and bentonite clay. It turns out that fragrance free kitty litter is mostly bentonite clay so I put some in a blender and pulverized it into a fine powder. Carefully mixing this with the sand and a small amount of water resulted in a nice batch of greensand that really held its shape well. The foundry was then heated up using Grant Thompson’s gas blaster (https://www.youtube.com/watch?v=eO8NwseRxSA) to a toasty 1700 °F. After about 25 minutes all the brass shell casings were liquefied and started to boil.
Once the brass starts to boil, it’s time to pour. This is probably the most stressful part of the project because I had to carefully lift the 1700+ °F graphite crucible out of the foundry and pour it into the foam risers.
After letting the brass cool for about 10 minutes I was able to dig it out of the sand and quench it in water. I was very pleased to see that the cast was successful on my second try and then began to clean it up. Taking the roughly cast emblem to a near mirror finish was a very time consuming task. I started by using an angle grinder to get the rough surfaces ground down.
Then I went through several different grits of sandpaper until I ended up with a matte looking finish.
Finally I was able to use a microfiber cloth and some metal polish to really clean up the logo.
I was curious what kind of brass was created from melting down the shell casings so last summer I took one of the leftover muffins to where I work (NIST). My supervisor had one of his colleagues perform an Energy-dispersive X-ray spectroscopy (EDS) analysis and it concluded that the sample was a pretty high purity yellow brass (70% CU, 30% Zn). If you are curious about the details of the analysis, here is the scan report:
While this artifact is a static emblem, I think it serves as a functional device that will bring back many memories of CU and my four years here. It also helped me to increase my casting skills as I learned so many new things about the whole process.
I am very pleased with the way the emblem turned out. I started this project envisioning a luxurious aesthetic to resemble the gold/black colors of CU. After an extensive polishing process I finally achieved a glossy gold finish that I think has a very luxurious look to it.
I plan to hang this emblem on my wall in my future office as a reminder of CU and where I earned my Bachelors degree. Before then I am thinking about sanding it down again and really working on getting the best finish on the surface that I can.