I have been keen to make some more plaster moulds, both to improve on what I have and to have a wider range of shapes available. A flatter elipse could look good though I would be concerned about strength so would need to insert struts inside. One of my larger 2 part spherical moulds is not spherical; it was made around a childs' ball, over several days. As the 1st half plaster dried it contracted, squeezing the ball so the second half plaster was around a larger form. OK but not good. In addition my carved shapes generate a lot of clay to be recycled so I needed a plaster batt too. So far, so straight forward, except that all the plaster in the department had been purchased before lockdown. Potters plaster comes with best before dates as it has a short shelf life. It absorbs atmospheric water and 'goes off'. All of the available plaster was almost a year past date. I tried making up a small test quantity and it seemed fine - smooth, no lumps, setting at a manageable speed.
I decided to make a batt. I got advice from Rob. I found the boards, put them on a base, plugged all the gaps, soaped the boards and measured out 10 litres of cold water . So far, so straightforward. Ten litres is a lot of plaster and takes a while to add then stir. As with clay, it seems that when you double the size you quadruple the difficulty. The small 'test' was not a realistic indication. Instead of a smooth plaster box I ended up with an interesting mountain range. I made more and thinner plaster to smooth it out but still needed to carve it flat. Never mind, I have a smooth and usable side for wedging when it eventually dries. I have ordered more plaster to make new moulds.
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AuthorI am indulging my passion for ceramics by undertaking studies for an MA at UCLAN Archives
August 2021
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