I just tried making a silicone mould from a master which all seemed OK but after I got the first piece out of teh mould there were a lot of dust marks on the  piece. I presume the dust had been attracted to the mould surface. Am I doing anything wrong?

FBS

The working are was not that dusty, and there was not a lot of time between making the mould and using it. Could it be static attracting dust?

Or, should I try another type of mould material. The silicone rubber is very soft and that makes cleaning difficult?