I had the great opportunity to visit Coade Limited near Salisbury. Stephen Pettifer owns the company and works with his team Alisdair, Hannah and Richard to produce award winning, high quality, Coade Stone replicas of original models, in addition to their own bespoke Coade objects and artifacts for clients throughout the world. Attention to detail of such a high standard, and every piece hand finished to perfection. No secrets shared, but I was allowed to see them work, ask many questions and may get to go back and spend a day hands on in the workshop.
Continuing on from my initial ‘salt dough’ model process I realised that those components would be too small to physically make any press moulds so I hunted various charity shops until I found the items which would be symbolic of those I had already used. Structural column, architectural design and aesthetic, and finally wealth to pursue. These can be seen in the glass vase, the casserole pot lids and the pineapple bottle stopper! Combined the components have the resemblance of a commemorative column or totum like that I mentioned previously of the Sir John Soanes Pasticcio.
First of all I needed to make plaster moulds of each component. The glass vase and casserole lids would be two part moulds and take one day each to cast, the pineapple was a four part mould and took 1 1/2 days to cast. I first had to construct a casting box. Potters clay was used as a platform for casting and moulding for the separate parts and Vaseline was used as a release agent. Natches were made in the plaster for relocation at the next stage (press moulding).
I then proceeded to make the plaster moulds for the casserole pot lids, both were slightly different and two part moulds were needed. I didn’t think through the fixing protrusions in enough detail and so one of the parts was cast in place! I had to try and hack it out without breaking the mould. Although the moulds seem very large it was because a 1 1/2-2 inch thickness was need to protect vulnerable narrow pieces of the original and withstand the forces of the clay/plaster and chemical reaction.
The final mould was the four piece pineapple. Each segment had to be marked up, areas of undercut needed to be masked off, and theleaves modeled separately. It was difficult to cast in the plaster because of the complexity of the shape and trying to keep it stable. As such one side of the mould was not as thick near a vulnerable joint and the plaster mould broke when removing from the original. One area of the pineapple has not been sealed off with clay entirely, therefore the plaster had seeped through to the base causing a sink hole on the external surface and thus a weak point.
I mixed four batches of Coade Stone Clay- they needed two days to settle before using. This had to be wedged before storage and wedged before use. (Wedged means to knead like dough and remove any air pockets which could cause defects when firing).
The plaster moulds needed to be thoroughly dry before press moulding the clay. After one week they were not dry. To dry out in the over the moulds had to be put into an oven at 45 degree C for two hours maximum, and allowed to cool within the oven. They were still not dry, I again put them in for another two hours and allowed them to cool down.
So on Tuesday evening the clay master objects could be struck from the moulds (following a 24 hour period of drying within the plaster mould). Some of the clay protrusions snapped off, some of the natches in the plaster for relocation weren’t big enough to secure the exact position and as a result the clay halves did not match well. I spent the next size hours fettling the objects. That is to say, you trim, infill, polish and smooth over any defects whilst the clay is still green, without damaging the main body.
… grand total of 64 hours and this is the result! four small but not so perfectly formed objects ready
to be kiln fired up to a maximum of 1050 degree C over a period of 38-40 hours.