There are 2 parts to this, firstly the original must be sealed and secondly a release agent needs to be applied. For the very best results its essential both are done very well!
Sealing the plaster original. The key to this is having the plaster as dry as possible. Shellac is the most popular well used sealer, however really needs to be applied to dry plaster. You can also use a 2-pack polyester primer, however this also needs to be applied to dry plaster and also it is thicker than shellac so you will potentially lose any fine detail on the original.
Users tell us that our ‘Jenkins Transparent Shellac Sealer S055’ is one of best shellacs to use against damp plaster.
Applying releasing agents; You need to apply a good quality wax release agent like Mirror Glaze at least 4 – 5 times, buffing it up and leaving it 10+ minutes between coats (the more times you do this the better). And then it is recommended you apply a thin coat of PVA Blue Release, this isn’t essential, but is definitely recommended for an easier release and less likelihood of damaging your plaster original.
Resin will stick very well to shellac! So it’s essential a good covering layer of releasing agent is applied.