Recently, I sealed a painting for a friend with some Rust-Oleum gloss spray. I really liked the finish, but I found it was a little difficult to maintain the same texture on the entire thing as I had no previous experience. So, I decided to do a little research (both theoretical and practical) and I thought I'd take you along for the ride with a series of varnish-related posts.
Why is varnishing acrylic paintings important?
Varnishing an acrylic painting is a very vital step to protecting it from the elements as well as from dirt, dust and abrasion. Acrylics tend to have a slightly tacky surface when dry and this, along with texture of the canvas/paint, makes it very likely for the painting to easily become dirty over time.
Varnish also boosts the saturation of the colours and helps to unify the sheen.
What type of varnish should I use?
There are two categories of varnish: permanent and solvent-based (removable). Under these categories, there are three different finishes: matte, satin and gloss. This choice is really just a matter of preference. Take a look at the second post of this series which talks a little more in-depth about the difference between these three finishes.
The choice between a spray and a brush-on gloss also becomes a matter of preference and which is more comfortable and effective for the user. I would absolutely recommend trying them both just for the experience. Spray on varnishes are guick and fun, but I find that I have a hard time creating a consistent look. Although, I can tell it's because I lack experience.
What is an isolation layer and should I use one?
An isolation layer is basically a film of gloss medium between your acrylic painting and the final solvent-based varnish coat. This is done using a permanent medium/varnish, preferably in gloss. Isolation layers are important to protect the painting in any situation where the final varnish layer must be removed due to cracking, abrasion or dust build-up.
Acrylic paints and solvent-based varnishes have a similar solubility range and therefore, the likelihood that colour will be picked up and shifted or removed during the removal the varnish layer is very high. An isolation layer is essential to prevent this from happening. It will allow you to remove your solvent-based varnish without lifting any of the paint underneath, and safely apply your new coat of varnish.
Do you use varnish regularly or are you also just trying it out for the first time? What's your favourite type of varnish?