Post 7 - Making a new oval mould

For some time I'd been thinking about developing a mould for an oval pot. In January this year I had some time on my hands at last and decided that it was time.

The first step is to make the equivalent of a casting pattern – a dummy of the final pot to be produced. This starts with a kind of armature over which a veneer of clay is positioned and then shaped to create the outer surface. Once this is done it is then a simple matter of building a dam around the pattern and covering it with plaster. Getting a good seal all ‘round is important.

 

Here it is just after the plaster is poured.

 

And then with the dam removed and the mould inverted into its normal orientation.

The oval shape you can see is the base of the armature which served as the template for the oval shape of the top rim of the pot.

 

This is the armature coming out to reveal the clay veneer which formed the wall shape.

 

Here the clay is being pulled easily away from the wall of the mould.

 Leaving a nice clean smooth surface for future pot moulding.

The mould inner dimensions are about 470 x 350 x 115 – remember it will come down by 15% to the finished fired and glazed pot.

As in slip-casting the plaster works by pulling moisture from the clay. It accelerates the initial drying and initiates the first of the body shrinkage. This releases the new pot from the mould. For this to work the mould has to be thoroughly dry before it can be used for the first time and that will take a couple of weeks.

Next on the agenda is the rather daunting task of glaze testing – about 100 different recipes coming up.