Is walnut oil really a substitute for mineral spirits?
This is a question I’ve been asked dozens of times through email, Facebook, and during our community webinars. It’s also a question I’ve had myself, which is why I’ve done so much research on the subject over the years.
For this blog post I’ve done my best to condense the information into a short and easy to digest explanation, but please let me know if more information or details would be helpful.
I like using walnut oil because it keeps the colors from getting that dry sunken look, but it doesn’t achieve the same watercolor like washes that we can get so readily with mineral spirits.
If we are planning to have the background wash visible in the final painting and want the colors to flow together like watercolors, then mineral spirits is a better choice than walnut oil. If we intend to cover most of the background with thicker paint and want our shadow pattern shapes to retain their more glossy appearance, then walnut oil or straight paint is the better choice.
Depending on how much we use, mineral spirit washes may not be entirely sound either because the mineral spirits dilutes the oil binder (walnut, linseed, poppy or safflower) and can cause the paint layer to become thin and weak. Since it has only been around since the 1920’s we don’t know for sure what effect it might have on our paintings. I wouldn’t worry though if you use mineral spirits – artists took to it like a moth to a lamppost and we haven’t heard anyone stomping around complaining that their investment art is falling apart.
Since I started using a tiny bit of walnut oil for my washes I haven’t really missed the mineral spirits – much.
I would caution not to use too much walnut oil, especially on acrylic gesso, because it will tend to bead. The reason it beads up is because of the nature of the mechanical bonding that occurs between the oil and the acrylic. Acrylic is plastic and porous – it has lots of tiny holes we can’t see with our eyes. The oil paint attaches to the acrylic by filling in and holding on to those holes. When too much oil is used, the holes fill up and the oil has nowhere to go so it beads up. At that point it will need to be wiped off and more pigment (paint) added to the mix.
If you decide to use walnut oil for your washes, take heart – there are artists from the 1800’s and early 1900’s who used soupy oil washes that have held up beautifully for more than a hundred years (not on acrylic grounds though, since acrylics are fairly young tykes – not used by artists until the 50’s).
Here’s an example of one of my recent paintings, done completely without mineral spirits:
Have fun and keep experimenting. And then let us know what you discover along the way 🙂