Water Level Controls and Devices. A water column is used on a steam boiler to reduce the turbulence and fluctuation of the water level so the gage glass can provide a steady, accurate water level reading. The use of a water column is not mandatory.
Preparation. Verify the paint is completely dry. Never use varnish to seal acrylic paint if it is even slightly wet. Dust the surface of the dry paint gently with a clean cotton rag or paper towel. Rinse a jar or cup with water to remove any dust particles. Read the label on your varnish to find the correct water-to-varnish ratio. Mix the varnish with water in the jar or cup.
Seal Mdf Edges Which Are the Most Absorbent. The edges of MDF boards absorb paint heavily. Make sure to seal these, especially if they have routed details. You can use an acrylic paint sealer or drywall sealer, or you can use glue or oil based primers which will help prevent the edges from swelling. Sealing MDF with PVA Glue-To seal the edges (or flat surfaces) you can spread or spray a layer of thin PVA (white or carpenter's) glue over the edge with a glue spreader, or a pump spray bottle or air brush, making sure the glue layer is as even as possible, with no build up at the edges.