As I mentioned in a previous post, moulds made for resin casting will be different from my lead casting moulds. Lead casting needs a funnel for the lead to pour down, and the weight of lead in the funnel causes the rest of the lead to fill the mould, preventing air pockets from forming. Resin is a lot lighter, so this doesn't happen with it, and the funnel is a waste of resin which unlike lead can't be reused.
This is a much smaller mould than I usually make, I think I probably make my moulds for lead casting thicker than I require because I'd rather be safe than sorry when dealing with molten lead.
This will be a one piece mould. The plasticine around the edge is to stop the rubber from leaking out under the Lego blocks, I think I have left enough flat around the model for the mould to work. This is my first attempt at this so I'm finding out what works and what doesn't by trial and error. The model was attatched to the surface by a dot of glue just in case it floats up through the rubber while it sets. Not sure that's a possibility, but why take the risk?