Making a two part mould
Reminiscing about my love for ceramics; that developed during last years lighting project , I was particularly excited to the begin slip casting process. Slip casting is a timely process, entailing a lot of waiting around for things to set and more often than not things going wrong. When working with any ceramics, I feel it is crucial to add a few extra weeks onto your schedule, to allow for things to go wrong- just like any process i guess! When it comes to slip casting, the main issue I had last year when slip casting was removing the casts from the mould. It took a lot of trial and error, and most of all- organisation! Once I had a system in place, I was able produce multiple casts; allowing me to choose the most perfected for my prototype.
Determined not to allow myself get caught up by things that could- and could not go wrong with my slip casts, I set myself a deadline of making by molds by the end of this week, which I did- yay! Before even getting down to the workshop to begin making my moulds, I needed to create a model of what I wanted to create. In this case, I wanted to make my plant pots- all twelve of them. I felt the best way of producing an accurate model, would be to first acknowledge my love-hate relationship with solid works. So, I prescribed myself some time in the 3D labs where I drew up my models- increasing their size by 15% to allow for shrinkage that may occur once fired in the kiln.
Once I completed my solid works model, I made my way to the make space to 3D print it. Unluckily, when I came to print it, I was having a day where anything that could go wrong did and after three failed attempts, it finally worked. Although, I did have to spend the morning cutting and sanding away the excess build up material around my model. This was quite a scary process as any damage done to the plastic would inevitably transfer onto the mould and then onto the slip casts themselves.
Once all the excess material was removed, I made my way down to the workshop to begin making my moulds. Having only ever made a once part mould before, I was really excited to learn something new. First, I needed to fill my plant pot with clay to prevent plaster from finding its way inside the plastic model. This would make the model difficult and would cause damage to the mould when trying to remove it.
I then had to build a clay wall around my plastic model. Then measure and mix some plaster together to create the first half of my mould- definitely the messiest stage of the process.
I then poured the plaster into the walls of the mould and waited for it to harden. Once set, I removed the clay walls and washed the first half of my mould with soft soap. Not only is this used to clean the mould, but it also creates a release between the two parts of the mould. This prevents to two pieces from becoming stuck together, when the second half of the mould is poured.
Having completed this, it was time to begin making the second part of my mould. Again, i built a clay wall around my model; ensuring there were no cracks that the plaster could leak through.
Again, I mixed fresh plaster and poured it between the walls to create the second part of my mould.
Once this was set, it was time for my least favourite part of the process- filing the excess plaster away from the mould!
After a very tiring hour or two of filing, I was left with my finished mould. I am very pleased with the quality of my mould, I am considering making a second mould the beginning of next week. This would give me a spare in the event of the worst happening to this one. It would also allow me to make two at the same time, doubling my chances of getting really well finished casts for my prototype.
Now, it is time to leave my mould in the drying cupboard over the weekend. I can't wait to begin slip casting my plant pots on monday!