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

Hi Ray,

Sorry for not posting the response on Friday but the cure took a little longer than anticipated (cool room where we did the test). What we found was that the Addition Cure Silicone cured fine in contact with the yellow wax; there was no inhibition at all.

• Incorrect catalyst ratio
• Not thorough mixing / insufficient mixing of the catalyst
  
• Something else caused the cure inhibition (some other material present on the bottom layer only)

It really can't be anything else. The subsequent pours cured fine so we know the silicone and catalyst are OK and that the ambient cure temperature is OK. We've tested silicone curing against yellow wax and that's fine too so it can only be one of the above causes.

I hope this helps.

Matt

Matt Statham
Easy Composites / Carbon Mods - Technical Sales