Trying to make my first silicone rubber mould I mixed and poured the first 110 grams of rubber into the mould box and in/around the object to mould. The first pour spread over a layer of soft filleting and filling wax. I continued with another 3 or 4 110 mixes of rubber to fill the mould box. When I removed the mould box after a couple of days at room temperature all the rubber had cured except the first layer which had been in contact with the wax. This remains soft even after a couple of more days in the air.

Is the wax the cause of this not curing or something else? If I should not be using a layer (5mm thick) of wax to pour on to is clay ok for this purpose please?

Regards