Mix 1 cup  cornstarch and 1/2 cup cold water. Add 1 quart boiling water, 3/4 cup sal soda, 1/2 cups ammonia and 1 tablespoon vinegar. Apply with a brush while hot. Rewarm if necessary. After varnish loosens, wash off with hot water and a cloth. If you don’t have soft water, it will work better if you add a softening agent to the rinse water.