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.
Acrylic. Acrylic paint is ideal on foam core because you do not need to use solvents like with oil paints. Acrylic it fast-drying, durable and adheres to most surfaces. It also has an even sheen and does not need a base coat.ome of the solvents in spray paint may damage the inner polystyrene in the foam board, so it should only be used on the paper exterior. Foam core boards are sensitive to moisture, and spray paint has less moisture than many other paints. It also dries faster than oil paints applied by brush.