Dear all.
A method I used many times when pattern making was to create a split mould from Dental plaster. You start by making a simple frame to act as a holder for the liquid plaster, pour some in and then sit the item to be copied, in this case a greased sphere into the centre to about half it's depth. The Dental plaster sets very rapidly and you will then have one half. You then need to create tapered indents into the surface to register the top half. Grease the top surface and pour in a top layer of plaster slip to cover and leave to set.
Dental plaster once set and thoroughly dried can be used to cast even Aluminium parts, I know, I have done it many times. Bismuth, a pushover !! If you are really careful this single mould can be used over and over !!
Cheers Grum.
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Nanny state ? Left at the gate !!
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