I tried to make another model out of plaster of paris. I made sure I sealed the bottom of the mould completely this time. I poured the plaster into the mould fine and left it for a 2 days to set. The trouble started when I tried to take the Aluminium mould off.
There were 3 problems-
- The plaster mould wasn’t thick enough. The object im casting needs to be done on a bigger scale (at least 1:2) with a wall thickness of at least 60mm. The walls I made were way too thin. At some points the wall thickness was less than 5mm. A slight knock and it crumbled.
- The 0.3mm Aluminium wasn’t flexible enough so I had to pull it off with force causing the plaster to crumble. Aluminium has the strength to hold its self upright, but it’s not flexible enough to fold back on itself like a sheet of paper or fabric. A rubber sheet would be ideal for a mould. See the video below titled “bending concrete” and you will see what I mean with the flexible mould.
- Too much water in the plaster. It was slightly soft to touch after 2 days of drying. Maybe the cold weather slowed down the drying process too.
I’m still confident that this process can work but I think it just needs to be done on a larger scale. Stronger materials and thicker walls.
Some parts came out of the mould alright. They were about 10mm thick and had very smooth surfaces. They are the 2 larger chunks you can see below).
The remaining parts are scattered on the lawn.
I had a feeling this wouldn’t work on a small scale from the start. But I had to try anyways. And at least I know what to do if I ever try this on a large scale. I will be making my 1:1 scale prototype out of different materials anyways because it needs to be transportable. Concrete would be great for the street sculpture but it won’t be suitable for the graduate exhibition.