Hi Philipp,

The problem with using a model board for a casting mould is getting the dimensioning perfect for applying a sealing coat of resin over the board itself.  Even with very high density boards, we would not recommend using the raw board as a mould without some kind of surface sealant to give a smooth surface.  Yes, with multiple layers of mould release agents, you can often get an ok release off high density model boards, but the mould life is short.

When sealing the surface, if you use a resin, you really need to try and take into account how thick your resin will lay. The nature of coating resins onto a surface means it is hard to retain dimensional accuracy and high levels of detail. Thinner coatings such as paint can solve the dimensional accuracy issue, however many paints will struggle to adhere perfectly and be tough enough for the rigors of use as a mould.

So taking this into account, if the loss of accuracy is ok, then you would be fine to use a coating resin such as our XCR Epoxy Coating Resin. It is easier to sand and shape than a typical epoxy resin, yet not as thick as a tooling gel-coat so will not loose too much accuracy.

In terms of release agents, I would almost certainly recommend using a modern chemical release agent such as our Easy-Lease Chemical Release Agent.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

Hi Warren,

PU600 is our densest board so will certainly be quite sturdy. For just casting the resin into, you would be fine with the PU 80 Low Density Model Board as you are coating the surface with resin to give a bit of strength and a sealed smooth surface, so you don't need a really heavy part.  If you wanted the mould to be highly durable then the PU240 would be the best compromise between weight and durability.

Vac Cast is a great resin for casting vac forming moulds.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant