Questions have come through YouTube and Email asking about walnut oil vs mineral spirits for underpainting washes, varnishing paintings, Turpenoid Natural for cleaning brushes, ABS plastic for panels, and watercolor vs acrylic paint to begin an oil painting. I answered each one the best I could according to the research available to me – which doesn’t mean something won’t change next week.
So spins the world of art materials research!
In the end, I don’t think any of us should get worked up about any of it or let it distract us from having fun and experiencing the incredible joy of being artists!
Some of the answers have been adjusted for clarity. Also, some questions overlap, but each has info that expands on the others.
Cleaning Brushes with Turpenoid Natural
Q. Jeanette: When cleaning brushes with Turpenoid Natural, do you squeeze it out and leave it in the brush?
A. That is exactly what I do Jeanette. I would not use Turpenoid Natural as a medium, but the tiny bit left in my brushes after squeezing them dry with a paper towel will not adversely affect the drying of the paint or the final paint film strength (at least that’s what I’ve been told).
There are no guarantees when it comes to art materials, but after 30 years of using Turpenoid Natural to clean my brushes, my paintings haven’t shown any ill effects from it.
In the 90s I would periodically clean my brushes with soap and water, but for at least fifteen years now it’s been only the Turpenoid Natural. My brushes stay in much better shape and many of them are over 10 years old and still razor-sharp.
Can We Use Avocado Oil for Painting?
Q. Rainbows: Thank you so much for the information! I always use Rembrandt oil paints. They are oily. Since you mentioned that you use walnut oil as painting medium, I was wondering if it’s OK to use avocado oil as a painting medium? I have some at home for soap-making.
A. Great question. You definitely want to avoid oils you would find in your kitchen. The difference between painting oils and kitchen oils is the drying rate and the strength of the paint film.
Walnut and linseed are the two primary drying oils – they will dry to the touch within days and form a tough skin that will not dissolve or smear (without using strong chemicals). Kitchen oils like avocado or olive do not dry and will always remain soft.
Safflower and poppyseed are semi-drying oils that can be used for oil painting, but they dry much slower and form softer skins. Safflower is better saved for cleaning brushes than as a medium because it does not form as strong of a paint film as the 2 main drying oils – or saved for the final layers in a painting if you really want to use it for some reason.
Then again, Philip de Laszlo used poppyseed oil, the slowest drying oil, for the initial underpainting washes in his quick portrait studies and 100 years later his paintings seem to be in great shape. Some paint manufacturers are using safflower and sunflower oils for certain paints like white because they yellow less, but it is not recommended as a medium.
Also, do not use safflower oil that you find in the grocery store because it is refined differently. Grocery store safflower oil is a high oleic acid oil that will not dry, while art supply safflower oil is a high linoleic acid oil which is why it dries and can be used for painting.
A Non-Toxic Solvent for Underpainting
Q. S: What paint thinner solvent do you recommend for an underpainting, that is non-toxic? Thank you.
A. For the most part, I stay away from any solvents like Turpentine, Spike Oil, or Mineral Spirits (if you feel you must use mineral spirits, I suggest Gamsol). When I want to add fluidity to my paint, especially for the initial washes, I use either straight walnut oil (artist-grade – not grocery store grade), Walnut Oil Gel by Natural Pigments, or a mix of Walnut Oil Gel and M Graham & Company’s Walnut Alkyd.
If I use walnut oil, I use only enough to make the paint fluid without getting it soupy (less than a teaspoon). If you’re concerned about the possibility of wrinkling from too much oil or the fat-over-lean dilemma – if you paint alla prima (you finish the painting while the first layers are still wet) that won’t be a problem because all of the paint layers are drying simultaneously, and those potential problems are dispelled.
Most of the time wrinkling occurs because of several interactions dealing with specific pigments, inferior materials, and environmental factors like excess humidity. Using thick layers in the early stages and then adding thinner layers over those a week or more later when those initial layers have started to dry makes paintings more susceptible to wrinkling.
We would need to use a lot of extra oil in the initial stages for our paints to wrinkle, which doesn’t usually happen because that much oil would make the paints difficult to work with. On the other hand, there are certain pigments like Titanium White, especially when used alone, that tend to wrinkle in thick layers (just watch what happens to an old palette when the colors dry for a couple of years).
The photo shows an old palette of mine I last used 7 years ago on a plein air trip. The Titanium White and Cadmium Reds did wrinkle, but the wrinkling looks like brush texture and isn’t really a horrible look. Considering how thick the paint is, any of the piles would fit right in with an impasto painting that was completed with hog bristle brushes. The most concerning thing for me was seeing just how much the oil that separated from the white paint yellowed. That is definitely minimized when it’s mixed with other colors because I have an impasto painting from the early 90s and the slightly off-white clouds look great.
The fat over lean concept is somewhat of a misnomer – one of the better articles that discusses fat over lean is found on JustPaint.org: https://justpaint.org/volume-weight-and-pigment-to-oil-ratios/.
As far as how much oil is too much nobody really knows – it’s best to experiment with our own paintings and see what works for us. Philip de Laszlo used so much poppyseed oil for some of his washes that you can see the drips at the bottom of his paintings and yet his paintings are in great shape 100 years later.
What Thickness of ABS Plastic is Best For Painting Panels?
Q. Jim: what thickness ABS do you use?
A. I like the 1/4-inch, Jim. I’ve tried the 1/8 inch, and it will work for smaller panels like 6×8 or 9×12, but they flex too much for anything bigger than that. The 1/4 inch will also flex a bit, but once they are in a frame, they are solid. I now use 120 grit to sand them and the texture is wonderful for oil painting.
Turpenoid Natural vs Murphy’s Oil Soap for Cleaning Brushes
Q. Teri: I am a watercolorist that is just beginning in oils. I have a set of Rosemary Ivory (synthetic ) bristle brushes. Would the Turpenoid or the Murphy’s Oil Soap be a good choice for cleaning them?
A. Both work Teri, but I prefer the Turpenoid Natural because it preserves the bristles better. Of course, with synthetics like the Ivory series you don’t have to worry about the natural oils in the bristles, so I would use whichever is most convenient for you. With natural hair bristles like hog or badger (Rosemary’s Masters series), I would stick with just the Turpenoid Natural.
Even Symi, Rosemary’s daughter, recommends Turpenoid Natural to clean their brushes.
Sorry, at the beginning of this reply, when I first saw “Murphy’s oil soap” I was thinking you were asking about The Masters Brush Cleaner. Be careful with something like Murphy’s because commercial products like Murphy’s may contain ingredients that are not compatible with the long-term health of oil paint films. Murphy’s oil soap doesn’t actually contain any oils and one of the primary ingredients is water. It may be fine, and I’ve seen other artists using it, but I’m a fan of sticking with products I know are compatible with oil paints like Turpenoid Natural.
Watercolor vs Acrylic Paint for Underpainting Washes and Varnish for Oil Paintings
YouTube Comments from LurklingX: FANTASTIC! Thank you 🙏 I made a summary of the info from your 2 vids, might help some folks who’d like a visual reference for non-toxic oil painting 😊🌟
• use paint straight from the tube
• use high-quality brands to make this work better (Michael Harding, Old Holland, Rembrandt, Natural Pigments/ Rublev, Gamblin)
• if you need some fluidity, use a little walnut oil or Oleogel.
• underpainting— use Oleogel, (or acrylics! Another vid recommended. Then use oils on top without issue.)
• clean brushes with Turpenoid Natural, or Safflower oil (some color might be left though)
My reply: Great summary! One thing I would modify – use watercolor instead of acrylic for quick-drying underpainting washes. Acrylics dry to the touch quickly, but they actually take 3-4 days to dry enough that it is safe to paint with oils on top of them (that includes acrylic gesso).
Watercolors on the other hand dry immediately and can be painted over with oils without any trouble or delay. Of course, watercolors don’t become water-resistant like acrylics, but once the painting is finished you can varnish over the oil and watercolor layers with the same varnish to protect both.
Another problem with acrylic paint is that acrylics dry with a much softer skin than oils and any dirt that settles over the years onto dried acrylic paint eventually absorbs into the paint film and is difficult to remove. Varnish helps with that problem, but watercolors avoid that trouble and are in most respects a superior option for underpainting washes, especially when painting alla prima or plein air.
I’ve used watercolor on lead-primed linen as an underpainting and it adheres beautifully and creates wonderful translucent washes for oil paintings.
Reply and Question from LurklingX: Oh my gosh! It’s so wonderful to get a direct response, I respect your work so much! 💜 I kept researching and found exactly what you were saying about the watercolors, but the varnishing part is an excellent point that I hadn’t thought of. Something I hadn’t seen yet in your videos was: is there a varnish that is not as toxic? Worried about fumes. Again, thank you so much for the reply and the additional information!
A. You’re very welcome! I use Gamvar to varnish. It does contain mineral spirits, but even with my super sniffer nose, I can barely smell anything from it. I don’t bother to wear a respirator or varnish outside because I don’t feel it is particularly harmful to my health like the others I’ve used. It is the least toxic varnish I’ve found. It does caution to use adequate ventilation, so those who are sensitive to mineral spirits will want to have an exhaust fan running while they varnish.
Winsor & Newton makes a similar varnish, but it smells awful and I wouldn’t use it without strong ventilation.
The wonderful thing about Gamvar is it allows the paint to continue oxidizing, so as soon as your paintings are safely dry to the touch you can varnish them – no need to wait 6 months to a year anymore!
How Much Walnut Oil To Use For Underpainting Washes
Q. Janis: I’m very new and have viewed quite a bit of the 6-week course and joined the membership, but haven’t yet run across how much oil you add to your paint. I purchased the walnut oil and tried to be light with it, but my first try was too much and didn’t dry after a few days. I don’t think it ever would have and it was just a trial on a small cheap canvas so no loss. I’m thinking I might need a dropper to not get too much in the paint. Thank you!
A. Hi Janis, I’m sorry to hear the walnut oil is causing you trouble. Hopefully, I can clear some things up for you.
First off, did you buy M Graham walnut oil? Don’t buy walnut oil from a grocery store because it is refined differently and will not dry correctly.
Linseed and Walnut are drying oils. Even if you use a lot of oil, they will each eventually dry. The main problem with using too much is that sometimes the oil will cause thick paint to wrinkle. While wrinkling is a possibility, I have several paintings I did in the early 90s with thick paint strokes up to 3/16 of an inch thick or more, and none of them wrinkled.
Philip de László painted from the late 1800s to the mid-1900s and used a very washy mix of paint and poppyseed oil to start his quick portraits and his paintings didn’t wrinkle. Then again, he painted alla prima.
Using a generous amount of oil for washes instead of something like mineral spirits works well for Alla Prima painting (painted in one session or finished before the first layers begin to dry). Wrinkling might occur if someone paints the first layers with a lot of oil and then once those layers are dry to the touch they paint layers on top that dry faster or don’t use extra oil. Alla prima painting overcomes that issue because the layers are all wet when the painting is finished and dry at the same rate – which allows the drying layers to expand and contract together, rather than at different timeframes.
One difficulty with using a lot of oil is that it can make the paint more slippery if your panel or canvas is already smooth and without much texture (and by “a lot” I mean a teaspoon or less. I usually dip a large size 12 hog bristle flat brush into the walnut oil a couple of times to get plenty on my palette when I’m mixing an initial wash of color/s).
Generally, I only use enough extra walnut oil to make my colors flow faster in the early stages of the painting so I can cover the white quickly and then I use very little or none at all for the final layers – using the paint straight from the tube without any medium.
Adding more oil to your paint does slow down the dry time, but usually by not more than a few days.
If this didn’t answer your question Janis please let me know and I will go into greater detail or try to explain it differently for you.
For more info on Alla Prima painting, you might enjoy: 5 OIL PAINTING TIPS FOR BEGINNERS
Blick Art Supplies carries Turpenoid Natural: https://www.dickblick.com/products/weber-turpenoid-natural/
Here’s a link for Walnut Oil Gel: https://www.naturalpigments.com/walnut-oil-gel.html