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Philippa Threlfall

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The ceramic relief murals of


Making a Mural

Philippa has often given talks about how she and Kennedy made their murals over the years. The photographs here were usually taken with this in mind. A well documented example of this process is the Exploration Obelisk in Bristol.

The mural panels on completion were to be about 12 feet high and the overall height including the sphere on top was to measure about 18 feet. For this sculptural piece drawings (below) at a scale 1:10 were submitted to the architect and client, together with a model (shown on the right) made of card, metal and wood. I was allowed to research for this project using images from rare mediaeval books kept in Wells Cathedral Chain Library.

Redcliffe Quay Obelisk Drawings

Redcliffe Quay Obelisk Model

When modelling begins, 10% has to be added to the work in raw clay to allow for the shrinkage which takes place during drying and firing in the kiln. We work with a grogged terracotta earthenware clay called Valentine's body. Grog is ground up fired clay and is added to stabilise the mixture. We often mix in a grey/white stoneware clay called St Thomas's body which fires at about 1120°C to a pleasing buff colour.

Flattened clay stuck to vertical surface

In early days I used to work on the floor, crawling about with hessian to divide the wet clay from the floor's surface. Later we began to use two inch thick polystyrene sheets as the backing.

The image on the left shows how the flattened clay magically sticks firmly to the vertical polystyrene surface as I model and texture away on an easel. The clay always needs to be kept damp during this process.

As well as adding clay coils and modelling the clay surface, I always use texture tools for pattern and richness. Kennedy introduced the idea of using rubber, resin and plaster press tools for impressing into the clay so buildings and details could be made more intricately and accurately.

Coloured slips (stained white clay) are often added at this stage to add variety later at the glazing stage.

Finished clay model

The design is then cut up into sympathetic shapes which will survive the firing process. Not all pieces are the same size, and the cut lines can actually help the finished effect, rather like the lead which delineates the areas of coloured glass in a stained glass window. The pieces of clay now resemble a giant jigsaw puzzle and have to be numbered on the back. A numbered drawing is made to use as a key when re-assembling later.

Tray with dried clay pieces

The clay pieces are now dried slowly to prevent warping and cracking and when completely dry they are 'biscuit fired' in the kiln to about 960°C. Clay fired to this lower temperature is pretty porous and can easily accept the glazes which are then applied.

Here a tray contains dried clay pieces ready for the kiln.

Glazing is an interesting process. There are so many variables: it is always a mixture of careful knowledge combined with a kind of creative go-for-it. I nearly always mix my own glazes, using metallic oxides for colours which give subtle and natural effects. All sorts of transparent and opaque glazes can be applied and rubbed away to bring out the richness of the clay. Lustres and oxides can be added and coloured glass melted into recesses in the surface.

Amongst the rich decorative surfaces, I always leave some calm areas: unfussy and/or unglazed. 'Plain and purl, plain and purl' as my great mentor Peggy Angus used to say. A knitting term for those who don't know!

Glaze being applied to the clay
Positioning the glazed pieces ready for the kiln

The glazed pieces have to be carefully loaded into the kiln because their position in the kiln affects the finished results. The glaze firing is at about 1120°C. Opening the kiln and seeing the results is always exciting. Sometimes the results are not quite right so pieces have to be fired more than once.

Gold and other enamel colours can be added at this stage and these are fired at a much lower temperature (about 800°C). Most 'raw' glazes appear grey or white. An octopus is seen in this picture with a raw glaze applied, which will appear grey-blue and brown once it has been fired.

Here the glazed creatures can be seen laid out on the polythene tracing. The pieces of ceramic are now being re-assembled for the last time, ready to be put into panel form.

This sculpture contained natural stone and at this stage stones were introduced into the background.

Glazed creatures laid out on polythene tracing
Collecting pebbles and stones

Many of our murals used (and still use) slate, pebbles and stone as a backing for the modelled and glazed ceramic. In early years it was acceptable for Kennedy and me to gather up stone and pebbles from the beach, and fortunately we did so in large quantities. I say fortunate because now this kind of activity can be seen as anti-social or even illegal.

Even after making many murals, we still have a good number of bags filled with various sizes and colours of pebbles. These are from both sea shores and river beds. We also built up a collection of slate from a worked out Cornish slate quarry.

In addition we have bags of different aggregates - stone from commercial quarries all over the country, of varying colours and crushed to different sizes. Aggregates are always 'legal', but they are tricky to obtain in relatively small quantities.

As seen here, the stones are sorted into boxes so that as we work we can select the sizes, colours and shapes we require.

Boxes stones sorted by size, colour and shape
Adding washed stones

The pieces of ceramic are now arranged with the washed stones on a board, as seen in the image on the left.

There is something of an art in sorting and arranging the stone so that it has a sweep and rhythm to echo the theme of the mural.

Here you can see the stone and pebbles being placed with the ceramic pieces into black resin mastic. This has to be done at some speed because resin cures quite quickly and the pieces must all be in place before the resin goes solid.

The resulting polyester resin and fibreglass panels can be made as a free-form shape or with straight edges as in this case.

Ceramic pieces and stones being placed in black resin mastic
Ceramic pieces applied to concrete block

It is worth saying at this point that the early murals, such as those at Leeds Bradford Airport, Greenwich District Hospital and North London Collegiate School, were made up in a different and more cumbersome way. In these murals, the pieces of ceramic and stone were placed into a cement render applied to concrete blocks. The resulting blocks were extremely heavy. This was an exciting medium but we could not assemble the panels in our studios.

Here, working on a wooden floor, Kennedy prepares the next resin panel.

Apart from any necessary cleaning, the panels are now ready for erection on the wall. They can be quite heavy and unwieldy so we rarely make them up in sizes larger than 6' x 2'. For many years, we tended to make panels to a size that would fit inside our Bedford camper van!

When erecting a mural, the panels are screwed back into the existing wall with brass or steel screws, which can be hidden with dabs of mastic so that they are hard to see.

This particular work was a piece of sculpture, with four ceramic panels forming the four sides of an obelisk. We worked in co-operation with master blacksmith James Blunt, who fabricated the supporting metal structure and made the armillary sphere which surmounts it.

The photos beneath show Kennedy and Daniel fixing a panel to the framework and Philippa emerging from the virtually completed obelisk.

Erecting the obeliskFixing a panel to the obelisk

Below is the finished sculpture which is still up today, located next to the floating harbour and between office blocks in the centre of Bristol. It can be seen over the river from outside the Theatre Royal, especially when it is flood-lit at night.

The finished sculpture