Excelsior Trade Decorators H2O Plaster Primer (Prices from)Trade Decorators H2O Plaster Primer A good pigmented water based primer with good hiding power and penetrating qualities suitable for application to dry, raw cement plaster, fibre cement and cement bricks with superior resistance to alkali attack and efflorescence. This primer is also suitable for use on gypsum plaster (i. e. rhinolite) that dries with a firm surface (not above powdery residue). This product has a low VOC compared to typical solvent