I’m using a 2 part addition cure RTV (room temperature vulcanization) silicone rubber that gives a flexible yet tough and reusable mould. The process starts by accurately measuring then mixing the silicone base material with the curing agent.
The silicone is highly viscose while the curing agent has the consistency of water. Not a good combination as its going to be difficult not get air bubbles in the mixture while stirring them together. If air bubbles get trapped in the thick mixture it could weaken the mould and worse, leave air bubble gaps on the surface of the object I’m moulding.
Here goes to pouring mixture into mould very carefully to avoid any more air in the silicone rubber, because unfortunately, there are loads of bubbles in the mixture.
This last photo shows the surface of the filled moulding box and it is evident a lot of air bubbles are in the moulding.