Vinegar is a popular solvent used around homes to remove all manner of stains. The acidic nature of vinegar makes it ideal for dissolving tough stains such as varnish or lacquer. Add ½ cup white vinegar to one liter of water to make a solution, and use a piece of cloth to soak the stain spot. You can wait for 10 minutes before wiping off with microfiber and then rinse with warm water.