A lifetime ago, I was at art college and worked a lot with plaster and casting. I love plaster, smooth slippy, and really useful.
Before that on my foundation I made one slipcast thing (actually two of the same thing). I modified a vase from a charity shop and made a plaster mould. Badly fired in an old waste paper bin, it still survives. I have always been a bit of a bodger. This is one reason why I am so in love with tiny pottery, it’s proper, real ceramics and glazes, but on a domestic scale – bodged to perfection in my kitchen.
So I’m looking for a way to reliably make the same thing over and over. I tried slab building small cups, but after taking 30 minutes each to make, they both exploded. I glazed one back together and use it, but I fell out of love with slab building quickly.
Next: Slip casting. I have always loved when you see plastic cups made out of ceramic, so I set my sights on paper sauce pots from burger joints. I started with Maccy D’s pots. These are small, but a good test. Intended to move on up to 5 Guys pots which are about 42mm high, will hold a good shot of booze, and will fit into my Microwave kiln.
Down my local high street I tried to get some plaster of paris, but could only find fine finishing plaster. Some of the internet said it would work. The rest, no so much. But I only take on information that matched my worldview, so went for it.
Here’s the plan:
- Plaster in paper cups so they are stiff enough to cast.
- PVA on the cups and a thin clay strip to reinforce the underside of the rim.
- Make a 2 part mould with openings in the top that will let me pour slip in.
- Make slip by stirring up all my clay offcuts in water.
- Dry mould
- Secure mould with band, pour in slip and leave to set a little.
My slip was a little runny/thin so it took a while to build up a thick enough skin. Before I started casting, the mould broke into 4 bits, but good enough for a test. Anyhow, 2 casts, one survived, proved that it will work in principle. Moulds in the bin! Amazon order placed.
Version 2: Bigger and better. Not really.
Decided that a one-part mould would also work I followed the same steps above with the plan to chip out the plaster from the cups. Chipping out the plaster took ages and damaged the walls. FAIL! And there was a bubble. In the bin!
Version 3: Softly-Softly.
So the next idea was to fill the cups with expanding foam that I have. This will make them hold their shape under the plaster, but be soft enough to pull out. Lovely, all so good. But then as I’m pouring the plaster I realise they are full of air and will rise up in the plaster. They rose up. Back to the drawing board? Nah, just hold them down for a bit and hope for the best.
Wahoo!! They come out perfectly, left a lovely impression and no bubbles. Brilliant. Really excited.
TODO: trim the rim and dry the mould before using them. That’s for next week.