This week I worked on finishing my medal. I cut out all the bronze from my tree, so I now had the task of grinding and polishing it all. This can be a very long process, but my pieces were quite easy to do because I was only working with the flat surfaces. I started by grinding off any of the remaining runners, and then grinding down the top a bit to get everything flat. I followed this by sandblasting to remove any residual ceramic shell. The sandblaster really brought the bronze to life revealing amazing colors of the metal, see below.
I followed this using a angle grinder with a polishing tool and the use of a air tool with a finer polishing tool on the end, which brushed the surface of the bronze giving a brushed effect as well as a beautiful shine. I finish the pieces with a final sandblasting. This finial sandblast removed any large scratches and gave it a matt finish which I really loved. I sealed the bronze using wax to stop the bronze getting unruly finger prints on it.
I also machined the new cast of the pewter. This time the results were far far better! Due to the accuracy of the pewter casts, I had no need to touch the sides of the rings, the only bit I had to do was the bottom, and this was easy because the jaws of the metal lath held the piece perfectly. Below you can see the beautiful shine of the pewter when it has been machined.
Once all of this was completed I had the task of joining and matching up the bronze pieces with the pewter rings. It was a long time since I had made the bronze pieces, and a lot had changed with the pewter rings since I got my waxes of the bark. I had based the bark outer rings on the old 3D print that I had done, since then I had done another 3D printer which was every so slightly wider and thicker. In addition to this I had made the bark ring out of clay which shrinks when it dries. Wax also shrink very slightly when it dries too, meaning the bronze pieces did not fit the pewter rings, they were too small, leaving a gap. Luckily I made 5 lots of the bark rings, meaning I had a lot of spare bits, so I ground down a small piece to get it to fit into the ring. This worked because all the bronze pieces had gaps where they joined, also due to this shrinkage, so you don’t notice the gap of the DIY piece! Below you can see the (unfinished) bronze pieces fitted to the shapes of the outer pewter ring.
The finial stage were not easy. I had to think of a way to fit the bronze pieces to the pewter rings. Initially I planned to drill a very small hole through the bronze into the pewter. I would then thread pieces of welding rod and screw it into the hole, using a tap and die to create the correct thread. However, I decided whilst this would be the safest and strongest method of securing the bronze to the pewter, I had little time before the deadline to submit my medal to BAMS, so I decided to glue the two together using Araldite. This wasn’t easy either. I had to make sure everything was in perfect position before applying the glue, and in a space of 5 mins hold the bronze in place using masking tape. Below you can see the result once the glue had finished drying.