This workshop was our second on the rotation after small metals. I enjoyed this workshop more than the small metals. I felt it was better directed and I enjoyed the process of making the mould for the casting process. We began by finding a non-porous object to cast. I wanted to set myself a bit of a challenge so I decided, rather than just doing a simple mould of a vase or a pot, I picked a pair of safety goggles as my object. This proposed some tricky implications. First I needed to find the centre line of the object, effectively cutting the glasses in two. However, due to their awkward shape I needed to treat the glasses as two sections; The lenses and the ear rests (temples). I began by embedding the glasses in a clay bed which rose up to half the height of the temples and followed their profile, only covering half their height. I also covered the front lenses to the same level as the temples. I then boarded the sides up and sealed it with clay. Following this I mixed the plaster and pored it into the moulds on top of the clay and waited it to dry.
Once it had dried I removed the side and took out the plaster and then the clay, flipped upside down and repeated the procedure, this time embedding the lenses in clay and pouring the plaster on top of the plaster that had just set. One must clean the plaster with as special soap wash to get rid of excess clay and to stop the plaster sticking to itself. I also needed to create little indents called Natches to lock the one part of mould into the other and stop it from sliding when casting. The final stage was to repeat this procedure fro the lenses, this time on the end of the temples I added a roll of clay as pour holes. Once that had dried it was ready for slip casting. I also added some extra pour holes for the slip at the front about the top of the lenses. The problem with these were that they were quite small due to how thin the glasses were. Another thing that was useful to note was how I had to pack out some parts of the glasses because they were simply too thin to slip cast. Once I had created the extra surface on the glasses, I needed to apply oil to the lay to stop the clay from sticking to it when I packed it out with clay before pouring the plaster in that section of the mould.
When the plaster was fully dry after spending a couple of days in the drying cupboard, I was ready do a slip cast. The first attempt did not go very well with not enough slip entering the mould and I ended up with half a cast object. This was because the holes for pouring the slip into were too narrow so the slip didn’t enter the mould quickly enough and it started to dry a bit so didn’t flow properly through the mould. To solve this I simply widened the holes a little bit to let more slip in. I also poured the slip in in a more controlled manner, directing it straight down into the hole and letting very little touch the sides. I also only poured it into the front two pour holes and didn’t put any down the rear two. This mean that the rear two acted as air holes so there were no air bubbles in the mould which helped the slip run smoother throughout the mould. I also angled the mould slightly down to help the slip run down the temples. The cast came out much better this time, however the temples broke off the main glasses due to the fact the join is simply too small, which is frustrating. But the main lenses looked really good. Due the the slow speed which I poured the slip into the mould the lenses had many layers on them where the slip had dried slightly in layers as the slip was poured in. I liked this effect and it reminded me of layers in rock.
I really enjoyed slip casting and the mould making is a very useful skill to have. I want to make another cast of the glasses to see if my third attempt will be the best, and I can actually get a full cast of the glasses pretty much as they were. I’m sure I will doing more casting work in the future and making more objects that require a mould to be made, such as casting concrete for concrete furniture.