Crafters can apply a coat of varnish over oil and acrylic paint to help seal in the color. One to three coats of varnish can also protect painted pieces from damage, and the smooth surface makes cleaning easier.
To apply varnish on top of paint, make sure the paint is dry. Use a paint brush to add one thin layer of varnish and let it dry. To add a second and third coat, let the varnish dry, sand the piece down with fine-grit sandpaper and add another thin coat of varnish.
Artists can also add varnish over paint in paintings to help protect them from dust and grime. To add varnish to a painting, use a brush to apply a very thin, even coat on top of the dry paint. Let the varnish dry for 24 hours before applying additional coats.