Video: Schmincke Primers The transparent primer allows watercolour painting on grease-free surfaces such as canvas, painting boards, wood as well as on acrylic paintings in which the surface remains visible - in comparison to the existing white water-colour ground, fine - and provides for especially creative options. The watercolour ground forms an even, matt, elastic and age-resistant film. Can be overpainted (or tinted beforehand) with watercolours, gouache or acrylic colours.