Hi Columbo
I note you recommend the use of vibration to shake the air out of the plaster - may I suggest another way of doing this that may be rewarding (or certainly worth trying)
Years ago my father and brother had a business that cast figures and building for model war gamers, and we used to cast in resin, but on the odd occasion we also cast in plaster (primary reason is although it does harden it can still be filed, shaped etc. allowing you to use the casting for making variants) - there are different grades of plaster - dentists being the hardest, and you can even add reinforcement in the shape of fibre.
To ensure our castings were bubble free, and avoiding unsightly holes and blemishes in the final piece we used a vacuum chamber to pull the air from the plaster or resin. This is best done in two stages - the fist when the plaster has been mixed and then once the plaster has been poured in the mould
Now before you panic, plaster only needs a couple of bar - 5 at most, and this can be achieved in stout plastic box - as long as you can make it air tight on the opening. 5 bar is achievable with a hand / bicycle pump...
lastly ensure you lay the mould on a perfectly flat and level surface to minimise warping. Note - you will get shrinkage with plaster to always slightly overfill and then be prepared to sand the back down - after the plaster has fully set!
Unfortunately my fathers business folded in the last recession and I no longer have access to the equipment to put a better step by step guide together here.
If any one wants to give it a go I would be pleased to hear of it, and help with anything I can remember (I used to work for my Dad every weekend in the casting shed - so have a little experience
)
GreenBoy
I note you recommend the use of vibration to shake the air out of the plaster - may I suggest another way of doing this that may be rewarding (or certainly worth trying)
Years ago my father and brother had a business that cast figures and building for model war gamers, and we used to cast in resin, but on the odd occasion we also cast in plaster (primary reason is although it does harden it can still be filed, shaped etc. allowing you to use the casting for making variants) - there are different grades of plaster - dentists being the hardest, and you can even add reinforcement in the shape of fibre.
To ensure our castings were bubble free, and avoiding unsightly holes and blemishes in the final piece we used a vacuum chamber to pull the air from the plaster or resin. This is best done in two stages - the fist when the plaster has been mixed and then once the plaster has been poured in the mould
Now before you panic, plaster only needs a couple of bar - 5 at most, and this can be achieved in stout plastic box - as long as you can make it air tight on the opening. 5 bar is achievable with a hand / bicycle pump...
lastly ensure you lay the mould on a perfectly flat and level surface to minimise warping. Note - you will get shrinkage with plaster to always slightly overfill and then be prepared to sand the back down - after the plaster has fully set!
Unfortunately my fathers business folded in the last recession and I no longer have access to the equipment to put a better step by step guide together here.
If any one wants to give it a go I would be pleased to hear of it, and help with anything I can remember (I used to work for my Dad every weekend in the casting shed - so have a little experience

GreenBoy