The rubber model has been tidied up and any flashing cleaned off. This was done with a new scalpel blade and the surface smoothed with a model-maker's hand-held drill turning at high speed various small grinding stones. I use a grinding paste of fine grit and water, and finish with Vim and water. Any other imperfections can be concealed with thin layers of silicone rubber - make sure the surface is grease-free.

The rubber model is put back into the plaster jacket (without the rubber mould) and the gaps between plaster jacket and rubber model filled with clay. It is important that the junction between rubber and plaster/clay is as near a right-angle as possible. This blunt angle reduces the chance of damage to the edges. The surface onto which the new plaster will be cast should also be as flat and even as possible, because this makes cleaning off the inevitable flashing (of liquid clay seeping through the joints) much easier. I have added two inches beneath the hoofs, the gap has been filled with clay and a new base board put in place.

Although this means working at the bottom of a narrow opening, as shown here, it is preferable to cast these internal segments before the big sides which hold all the small parts together. Plaster expands as it crystallises. Not much, I admit, but enough to force the other segments apart. Even a small segment, such as that over the ears, can force two big sides apart and lead to leaks of slip from the production mould.

The existing plaster has been well soaked in water before assembly. Old plaster which has dried can suck water from liquid plaster as it is poured, so that the resulting new part is ruined. The surface of the old plaster must, in addition, be well covered with the parting agent. I use clay slip, but this is not a barrier to the suck of dry plaster.