Can I just cheekily drop this product link in here. I have no affiliation or anything like that.
It is however a resin casting powder, 3:1 mix powder and water so a lot easier to mix up a tiny amount and bring far more liquid when mixed it gets into your molds easier!!
Mods delete link if inappropriate.
I prefer to make a mould that sits in a removable wall. So if you make a wall around the mould to form the mould in say lego and the slice the sides just stick it back in lego when you cast. You then don't get any issues of warpage that tends to happen if you try another method to keep the cut sides together.I'd make a one piece mould with the wall upright like in the barrier example and then cut down the sides with a sharp knife if the casts don't come out easily due to overhangs. Then just wrap parcel tape around the mould to hold the cut edges closed before pouring the resin/plaster.
Really it’ll depend on what you’re doing with it. If you’re just using it as detail to line a passage or wall or whatever and will only ever see one side then just do it as an open faced mould. If you want both sides visible then the way the guys have described would work if you didn’t want to go through the process of making a two-parter.Wee question for @cardyfreak and the other venerable experts here; if wanting to cast an already-built ZM bulkhead or wall in plaster, would you recommend a single side mould (much like the two barriers in the original example, with the item standing upright in the chamber) or a two-sided mould (with the wall or bulkhead on its side)? They seem ideal for a single side mould, except each does have a slight overhang, so I'm not sure how to proceed.
I prefer to make a mould that sits in a removable wall. So if you make a wall around the mould to form the mould in say lego and the slice the sides just stick it back in lego when you cast. You then don't get any issues of warpage that tends to happen if you try another method to keep the cut sides together.
I like making them on the lean side but always cast with lego walls in place. Get more moulds out of any given amount of rubber that way.Yeah this is more ideal tbh. The tape is more a quick and easy option. Depends how thick you make the walls of the mould too. I like to waste rubber making them way too thick.