When you finish your painting, you'll probably want to varnish it. A good varnish will add dust resistance and a protective final coating, but it's not necessary. Besides, varnishing your painting is an excellent way to improve its appearance. Most modern-day brands have UV-light-resistance, which will prevent it from fading. Most varnishes are acrylic, though some are water-based and are removable. It's best to use a properly ventilated space when applying varnish.
There are many types of varnishes, each with different purposes and effects. Professional Satin Varnish is one of the most common types of varnish and is a superior choice for painting. This type of varnish is UV-resistant, but it is not removable with Artists' White Spirit or Distilled Turpentine. Retouching Varnish is a UV-resistant gloss varnish that provides temporary protection for oil paintings. It dries quickly and should be applied in thin layers. Once you're satisfied with the results, you can remove the protective varnish, and restore your painting to its original state.
Before varnishing your painting, you should prepare it for it by following the steps laid out under “preparing your painting.” You should also wear a mask with air filters, as varnish fumes can be harmful to your health. Check the canvas surface for any contaminants. Once you've finished varnishing your painting, you should leave it out to dry. For a fast drying effect, you can leave it out in direct sunlight.