Similarly to the ceramic bow I used the wooden bowl as my former, except after a few goes it wasn’t as crisp as I would have wanted. So using the illustrator files I already had I cut the same pieces in acrylic. I picked 5mm instead of 3mm like the former for the ceramic bowl. I used different thicknesses to hopefully compensate for the shrinkage of the ceramics. As the ceramics bowl needs to sit inside the bronze bowl it needed to be smaller. Although new earthenware roughly shrinks between 6% and 10%, it was to vague of a guess to work out so I made the ceramics first and up scaled the bronze slightly to counter the shrinkage. I was hoping the shrinkage of the clay and difference in thickness would be enough, I wasn’t far off. I know I should have taken the time to further work it out but I did not have a lot of time left on the project and I was very fed up with the complex mathematics I was already using. They fit together but it could fit better. If there was time to re do the bowl and improve it i wold work out the shrinkage rates properly and make them fit perfectly.
- The first task was to cut the acrylic bowl in 5mm.
- Then I bevelled the edges to the same angles at the previous MDF bowl.
- next I glued and filled any gaps where I had sanded too much away.
- The next step was to use the bowl as a former in a sand mould. This is a bronze casting technique which creates a solid carbonised sand box allowing, molten metal to be poured in to the appropriate shape. (see hand book for method. p29-32)
- After the mould is made and the acrylic mould removed leaving a negative space. i was able to complete the bronze pour and make the actual bowl.
- The bowl poured perfectly, the straight lines and accuracy of the acrylic produced a very precise bowl. The extra bronze in the photos is the excess material that bubbled up through the pour hole and air holes.
- The next steps were to refine and polish the bowl, using and angle grinder with a cutting disk, I removed the excess bronze leaving just the bowl. Some of the edges were a bit rough due to easing the former out of the mould. So I sanded both with a air pressured sander and with a hand file to really perfect the edge. Unfortunately the Bronze pour happened a lot later than I had planned for. It is very easy to spend weeks finishing bronze and I did not have that much time to spend on the bowl.
- After the edges were smooth I then polished the whole bowl up on the large polisher in the metal work shop. I found it really shined up the surface without taking to much of the texture from the sand mould away. However the polisher is a fairly large disk and i could not reach inside. If I had more time then using smaller dremle I would have tried to polish the inside but as i was on to the next project i just worked on the outside.