Pressing, draping and pre-cut slabs

The tableware range included square, octagonal and oval platters and these were generally formed using a press mould or a drape mould. The master shapes were formed from plaster or wood (stacked particle board, waxed to aid releasing). The drape moulds allowed us to attach a foot immediately while the press moulds usually had an extruded rim and handles attached. Platters that are not as rigid in form as when using the drape or press mould can be formed by laying a pre-cut slab of clay over a large sponge and then pressing a shape down into the sponge. This technique is very useful when the slab is to be decorated before pressing. It allows techniques like screen printing, mono printing, underglaze colouring or slip decorating to be done while the slab is a flat surface. The clay needs to be firm enough to hold the fluid shape when pressed.

Using simple one-piece moulds allowed us to make many functional shapes but eventually
we wanted to escape these boundaries. Along came the idea of pattern making and construction techniques. Pots were designed and turned into a number of thin wooden flat patterns (a la dress making). The rolled slab was cut into the required pieces and stuck together using slip (clay, toilet paper and vinegar) without any supporting form. The tricky bit here is getting the clay stiff enough to stand up during construction but soft enough to work with. The clay slabs can be stiffened relatively evenly by laying them on cement sheeting.

Clay as a canvas

Slabs, in their simplest form, make a great canvas. They can be painted upon (glaze over glaze after bisquing or underglaze colour when raw) or printed (lino-cut or silk screen). They can be carved, added to or textured. Unfortunately, they are as daunting as a blank piece of paper. They say absolutely nothing in their raw state so it is all up to you.

Really thin MDF (2-3mm medium density fibre board from any hardware store) makes great lino. It is cheap, more than large enough and easily worked with normal lino cutting tools and the board can stand being rolled onto clay slabs many times. Draw your intended image directly on the board in preparation for carving. When rolling through the roller use ‘glad wrap’ as the release agent between the clay and the master.

Silk screens are made from drawings and photographic images that have been manipulated (simplified) on the computer. The image is screened directly onto the raw slab using a mixture of honey, glycerine and oxides for the ink. This is applied with an old credit card and the ink needs to have a ‘tacky’ consistency. Often, more than one screen is used to build up the desired composition.To reduce the occurrence of cracking during drying, we wax about 2-3 cm of the edge right around to even out the drying across the slab

(Right) A face was built up on an otherwise flat slab. The slab was carefully slapped down (face up so to speak) on the concrete floor to stretch and manipulate the image. Once acceptable, it was then placed over a hump to give the face some form. This one was raku fired. Our garden is home to a great variety of birds, both of the feathered variety and the stoneware variety!

Multi-piece mould

We make vessels up to 1 metre high using this method. This teapot (above left) is made using a two piece mould. The body is press moulded as two halves then brought together face to face and placed over a slab base. The tricky bit of this operation is creating the moulds in the first place. I had to make a master from which the two working moulds were cast.

(Left) Step 1: Dream up the shapeStep 2. I set up ribs of wood to guide me in the making of the plaster master.

Step 3. Fill in the ribs with plaster to create the master, in this case half of the teapot body. When set, paint with softsoap as the release agent.

(Left) Step 4. Cast a reverse copy by building up about a 5cm layer of plaster over the master. This requires good timing. As the plaster thickens it can be built up over the master without the need for an excessive clay dam or excessive plaster thickness.

Step 5. Repeat step 4 to get the other side

Summary

We have found slab pots extended our range of work. They added shapes and styles that were not only good to look at but a little out of the ordinary. The roller is by no means the fastest production method but it offers immense flexibility especially when combined with extruded and thrown parts. It can be used in a pure artistic sense right through to a production tool.

Photography: Ric & Judy Pierce