The first casting, and a lesson learned…..

Photo 02-04-2013 12 13 10Just over a week ago the mould seemed to be dry enough to pour a slip cast. The only slip I had on hand was a white grogged clay. Grogged means the slip has small bits of crushed fired clay mixed in, giving it a grainy texture – it helps to prevent shrinkage when drying and firing, and cuts down on the chance of air pockets forming in the clay. This slip will be fine for the test, it’ll dry pale enough to be used as a base for the liquid light, it might be a bit rough due to the grog, but we’ll see….

The mould was sealed up around the join with some clay, just in case the slip leaked out the side, and a thick rubber strap held the two halves in place. The slip was poured in through the pour hole. As the plaster mould absorbes the moisture in the clay the clay sticks to the side of the mould, and the level of the slip goes down, so it needed constant topping up.

The longer you leave the slip in the mould the thicker the walls of clay will be, I left the slip in the mould for 5 minutes then poured out the remaining slip, leaving it to drain upsidedown over a jug. A few minutes later the mould was turned the right way up and the slip cast was left to dry out and the clay to stiffen up……

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Top left – mould sealed up : Top right – slip poured in : Bottom left – left to settle : Bottom right – draining the slip out

A few days ago I was checking to see if it looked dry enought open, and it did, I got excited and wanted to see how it looked, so I opened it up ……

2up

opened up mould

It looked ok – a bit rough, but then that was my fault fot not taking the extra time to smooth the release agent on the ball. The pour hole, where the slip was poured in looked good, big enough for the liquid light and chemicals later. There seemed to be a gap between the clay ball and the plaster mould – it had shrunk as expected, and I assumed that the clay ball was dry enough to remove…I tried to pull it out, it gave a little, I banged the base of the mould, nothing, so I took hold of the top of the ball and gently twisted…….

This is where the first lesson comes in – it appears I am too impatient – the clay had not dried out properly on the base, and as the ball came out the mould it left behind a big chunk of still wet clay, firmly attached to the bottom of the mould…..

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Lesson no1 – I’m too imapient – let the clay dry properly next time!

Although a bit of a fail, this is not all that bad, it has given me an idea on how the balls will look with the front broken away (picture on the right above) showing the image on the inside, and it looks pretty cool, so that’s good.

(I know I’m impatient, and I think when I do these at full size, I’m going to have to make a load of moulds so I can make several cameras at once)

After a few swear words and giving myself a ticking off for being too imaptient, I poured up another slip cast, not crying over spilt cow juice and getting back on the horse and all that.

Photo 04-04-2013 11 00 41

take 2

Take 2 – Lets leave this one longer……

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