How to Varnish an Acrylic or Oil Painting

Varnish is more than simply a layer to protect your painting from pollution in the atmosphere and abrasion. It will also bring out the colors to the brilliance they had when you applied them.

Difficulty: Average

Time Required: Depends on size of painting

Here’s How:

Ensure your painting is completely dry. Allow several months for an oil painting to dry properly. Depending on the thickness of the paint, this could be up to nine months.
Clean the painting so it’s free from dust, dirt, and grease. Lay the painting flat, then dampen a bit of cotton wool with clean water.
Dry the painting with another bit of cotton wool. With your fingers, gently remove any cotton fibers that have been caught in the paint.
Leave your painting to dry for several hours, or overnight. Lean it against a wall, face inwards.
Use a flat bristle brush to apply the varnish. If you don’t want your painting to be too shiny, use a matt varnish rather than a gloss one.
With the painting flat, work from the top to the bottom, applying the varnish in parallel strokes from one edge of the painting to the other. Always work in the same direction.
When the first coat of varnish is dry, apply a second coat at right angles to the first. This will give you a good, even finish.
Leave the painting flat for at least 10 minutes after you’ve finished varnishing to stop the varnish running down the painting. Then prop it up against a wall to dry, face inwards.
To test whether the varnish is dry or not, touch the edge of the painting to see if it’s still tacky. It should dry within a day or two, depending on the weather.

Tips:

Always varnish the whole of the painting in one go. If you do only a part and this has started to dry before you do the rest, you’ll end up with a line where the first bit ends.
Try to have the same amount of varnish on the brush for each stroke so you put equal amounts of varnish on all parts of the painting.
Work in a dust-free environment, otherwise dust particles will get stuck in the wet varnish. Keep cats out too; being so inquisitive, you could end up with paw prints in your new varnish.
If you’re too impatient to wait several months for your oil painting to dry so you can varnish it, you should consider using acrylics.

Visit http://painting.about.com for more details.