Experiments in casting

I wanted to make a “stone” version of a form I have made often as jewellery, the Reuleaux Triangle – the original form developed by the mechanical engineer Franz Reuleaux  in the late 19th century.

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  • I needed to mark out my new wok – I couldn’t  find a set of dividers large enough – 25cms, so I made a very simple one from strips of wood. I borrowed a wing nut, bolt and nut from something else, cut two pices of 30cms and one 18cm long, drilled some holes at roughly .5cm intervals on the short piece and used two nails to fit them together, added some points just with sellotape.
  • I marked the wok roughly in blue felt-tip pen and then found the centre-point using the dividers, drew a circle, divided that into six. I drilled a small indent at three of those points and used those as the centres to draw the three arcs.
  • I made Plasticene walls along the scored lines and set a  saucepan lid at the centre to form the central hole. I hoped that brushing the whole thing with petroleum jelly would make it easy to remove when set.
  • Using Cassini’s plaster from Maragon,  I mixed up a test bacth that was enough  to coat only about half  of the mould, I added progressively both by making more mixture but also by scraping the surfcae and using that to infill gaps. Not a good idea as it turned out.
  • The plaster becomes very hard and waterproof after maximum of 5 days but is workable to varying degrees for 2-3 days, at 15 minutes it seemed a bit like cheese, almost rubbery and not easily spread out or carved, though i did try to scrape the surface smnooth with a swan-necked cabinet scraper and what is charmingly called an Alabaster Knife from Tiranti, sculpture suppliers in London
  • 24 hours later it was dry enough to slip clear of the wok, petroleum jelly works but the uneven inside surface was terribly difficult to work on, dimpled, rough and flawed and the outer surface was marked with poorly patched areas, badly mixed plaster (small inclusions of plaster dust), rust and ink stains as well as bubbles!
  • So – it had to go in the bin . . .