Having in the past been involved in Military Modelling and produced White Metal parts for various Manufacturers in both Germany and UK, I have some knowlege of Hot Metal!! It is dangerous, very dangerous! My casting temperatures were between 250 and 280° C. all moulds , which were of Silicone, were warmed first, so no chance of moisture, which can cause the mould to spit back, with nasty results! I tried Plaster of Paris Moulds for keel weights but it was a very Iffy method as the mould absorbs moisture when not in use and needs to be placed in an oven to dry out. If you have pored into a wet mould and got away with it, you have been very lucky!
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By the way, anyone want some 1\72 Napaleonic figures? The last Company I supplied has folded ( Owing me for the last 2 deliveries!) and I still have their moulds, crews for galleons? Joking aside, be very careful hot, metal doesn't take prisoners, a drop the size of a pea will burn right through an unprotected hand.Always wear stout leather gloves and eye protection, please. As a matter of interest I used to pay between 12 and 17 pounds Sterling a Kilo for my Casting Metal, depending on quality.