Matisse Acrylic Medium MM12 - Clear Sealer 250ml. MM12 is specially formulated for folk art techniques. This Medium is primarily used to provide a clear sealant layer to substrates. Clear Sealer can be used on raw wood if you are not using a Matisse Background Colour (which has a built-in sealer) and want to paint a design on the raw wood leaving the natural grain revealed. MM12 Clear Sealer will block tannins from wood bleeding through subsequent layers. It can also be used on glass, ceramics, terracotta pots and new metal. All surfaces should be clean and dust-free before MM12 Clear Sealer application. For porous surfaces such as wood, terracotta pots, unfired ceramics, etc. Apply diluted with up to 1 part water to 2 parts MM12 Clear Sealer. Matisse Clear Sealer is water-resistant, quick drying and flexible.