I am producing a silicone mould using RTV addition cure.  We have created the mould previously using an aluminium plug but needed to be altered.  We have created a GRP plug and used plastercene as an infill.  However, all avound the GRP the Silicone hasn't gone off but has left a sticky and bubbling resedue.  Could you advise why this was and how I can resolve the issue please?