Information on Permanent Rubber Models.

LENHAM POTTERY MODELS
making high-fired semi-porcelain models since 1969

Additional information on pottery mould making and slip casting ceramic models

Back to
Lenham
Pottery
Models
Home
Page.

Back to
Horses
Introduction

Permanent Rubber Models:

When I began, in 1970, I made my horse models, on an armature, out of clay. I made the intermediate mould out of fibre-glass in removable segments which had to be 'stitched' together with wire. Into the horse shaped hole I poured a melted thermoplastic material, Vinamould or Gelflex. This had to be heated in a double skin saucepan (I used a porridge cooker), with oil instead of water in the lower pan. The hot compound had a vile smell and eye-watering smoke. It seemed to be based on paraffin wax. When kept for several years, the surface grew a skin of white wax which had to be washed off with hot water and detergent. As the picture, right, shows, the rubber surface can be deeply engraved to resemble long hair. This texture cannot be transferred to the mould except with a flexible compound which will not ruin the plaster when the model is taken out of the mould. If bits of clay model get pulled off by the mould, then they can be modelled back again.

In the related set of pages on the discontinued models, there are photos of dog models made of thermoplastic rubber. This is the yellow Vynamold.

Models made of Gelflex could be smoothed after removing from the intermediate mould with a hot blade. I used a modified pyrography tool.
Some models have been used many times to remake the production moulds. That is why it is important to have a model which will remain the same shape through several years of storage and occasional re-use. Cutting back the edge of the clay bed or the parting agent means that a slip from clumsy knife edge does not disastrously damage the model if it has a tough surface. It is also helpful to have a contrasting colour for model and plaster mould. Even though I may use white silicone rubber, I usually tint the first coat (visible on the outside) with a dark colour.
The reason for a flexible rubber surface to the model is demonstrated by the picture of the Lhasa Apso above.

Back to Step Four .