Pitting and bubbling artefacts in surface replicas made with silicone elastomers

Pitting or bubbling on the surface of epoxy resin replicas is a frequently encountered artefact associated with the use of silicone rubber impression materials. Several variants of this type of artefact are illustrated. It is suggested that bubbles or pits form at the mould:epoxy interface during curing of the epoxy, and that they are caused by gas escaping from the mould material itself. Duration of silicone rubber polymerization, base-catalyst ratios, and surface porosity of the object may all influence the occurrence of mould degassing.