For many years, the consensus was that acrylic paintings didn’t need to be — or couldn’t be — varnished. But in the last couple of decades, conservation science and technology have developed varnishes for the acrylic medium.
Artists’ acrylic paint, when dry, is porous enough to collect dust and dirt. And any paint film may fade with too much exposure to the ultraviolet rays in daylight. Varnish protects against these problems developing.
With acrylic paintings, however, it’s important to apply an isolation coat before varnishing. The isolation coat provides a physical barrier that the varnish — and subsequently used cleaning fluids — can’t penetrate. So, if and when the varnish accumulates dirt and needs replacing, a conservator can remove it without lifting colour or otherwise harming the paint surface.
Applying an Isolation Coat
This coat is laid before varnishing, so that the varnish can be removed later (if necessary) without damaging the painting by lifting off acrylic colour. Some varnishes are permanent — non-removable.
If you use a non-removable varnish and, years later, it yellows or accumulates dirt, you’re stuck with those problems forever. It’s better to use an isolation coat and then apply a removable varnish.
Steps to Follow
- Find a wide, low dish/tub to hold the mixed isolation coat for applying.
- Mix, then measure out enough product for the painting. Golden says to use one ounce per square foot to be covered.
- With a fine-haired brush at least two inches wide, load it to 1/3 to 1/2 the bristles’ length. Apply a series of “sevens” across the painting surface. When applying the product, use both sides of the brush alternately.
- Brush over the figure-sevens in one direction across the painting, to near the edge only (to avoid slopping product over the edge).
- Cover the periphery by working from the outside in.
- If needed, use the brush to pull excess material for an even coat. But don’t overwork! To avoid bubbles and brushstokes showing, stop while the entire surface is still wet.
- Leave to dry for two to three hours (24+ hours until you varnish).
- Inspect the coating. If there are dull spots, apply a second coat.
Applying Acrylic Varnish
[This section coming soon.]