Stepping into an art supply store can be like a kid wandering into Willy Wonka’s factory—suddenly, everything is a “must-have,” and we quickly calculate if our mini-van will hold everything we “need”! It’s a wonderland where every shelf promises new creative achievements.
It’s easy to get swept away, imagining that each tube of paint or brush could unlock the masterpiece within us.
Yet, as exhilarating as this shopping spree can be, it’s crucial to approach these tools with a discerning eye—especially when it comes to the seductive, yet potentially deceptive, promises on the labels.
Like a cat on a hot tin roof, navigating the world of art supplies can be precarious. We’ve all been enticed by products that claim to revolutionize our art, only to learn that they bring more complications than solutions.
As seasoned artists, we know that the choice of materials is as critical as the strokes we lay down on the canvas.
Today, I want to discuss three art materials that I’ve used and that often find their way into oil painters’ studios. While they may have their benefits, these materials should be avoided or used with caution to ensure the longevity and integrity of your artwork.
The culprits? Zinc Oxide, Clove Oil, and Solvents.
Zinc Oxide
Zinc Oxide, often celebrated for its brightening properties, comes with risks.
Zinc may promise to add a sparkle to your work, but it could leave your artwork cracking under pressure like an overcooked soufflé. It’s best used with caution—unless you prefer your art pre-aged for that antique look 😁!
Those of us aiming for longevity might want to steer clear and bypass zinc altogether.
The concern stems from research conducted at the Smithsonian Museum by Marion Mecklenburg from the late 90s to the early 2000s, suggesting that zinc can cause oil paint to become brittle and delaminate (peal) over time. One of the best articles I’ve read about zinc is found on JustPaint.org.
George Hanlon of Natural Pigments is another fantastic resource for information on art materials. He has seen first-hand the conservation nightmares that support the Mecklenburg studies that caution against using zinc in oil painting.
What about the lifetime supply of Permalba White resting in your drawer, you ask?
Permalba White is a popular titanium-zinc mix that has been a favorite among many artists. While it’s the top-selling white of all time (I don’t know if that reflects the quality, or the fact that it was created in 1921 as the first ‘safe’ white to replace lead white), it’s important to consider its zinc content, which could potentially compromise your artwork.
Tubes of Permalba White in a drawerUnless you’re Joy, one of our community members, who’s been using Permalba White for 70 years (yep, that’s not a typo). She’s used the same white for seven decades, and none of her paintings have cracked.
And let’s not forget prolific master painters like Dan Gerhartz and Richard Schmid, who both used Lefranc’s zinc-laden whites extensively without any known problems. —except when other factors, like fugitive pigments, come into play.
For George Hanlon and Marion Mecklenburg, the choice is fairly clear—stay away from zinc. However, for those of you like Joy, who have been using zinc-containing paints like Permalba for decades without noticeable issues, the decision might not be so clear-cut.
I find it interesting that, try as I might, I have failed to find a list of more than one or two paintings in the last 100 years that have suffered the terrible consequences described in the articles, and none that have been painted on a traditional oil or lead ground.
They’re probably out there, but I couldn’t find them. Every paper or article I’ve found talks about the tests done with zinc oil paint mixtures on acrylic grounds or polyester, not oil or lead primers. There isn’t an overwhelming display of evidence available to the public showing widespread damage from zinc-based paints.
Maybe painting on a lead or oil-primed surface you prepare yourself rather than an acrylic-gessoed canvas could mitigate potential issues, though research is obviously needed to confirm this.
Also, I purchased a large roll of lead-primed linen almost 20 years ago. A couple of years ago, I discovered that almost every major oil or lead-primed canvas manufacturer uses zinc in their mixtures. So, unbeknownst to me, I’ve been using zinc canvases for decades (yes, that includes Claessens). Fortunately, none of my collectors have returned a painting due to cracking or peeling.
That’s why I’m not offering a solid opinion. In light of this, if you use zinc in your primer or paint, do so knowing the risks.
Ultimately, as with any artistic tool or material, the best approach is a balanced one. Know the potential pitfalls, but understand that not every warning applies universally. If zinc white has been part of your palette for years and you’ve encountered no issues, I wouldn’t panic and throw out your expensive stash of paints.
Take a cue from Dori and “just keep painting” and be grateful for the beauty these materials help bring to life.
A little aside – materials can cause significant defects:
While attending the opening of a show one of my paintings was in at the Bennington Center for the Arts, Richard Schmid gave a lecture lamenting that he was in the middle of working with conservators to repair a large painting of Nancy in a red velvet dress. It began cracking extensively a few years after painting it (a painting that sold for $150,000).
The cracking was caused by the large amounts of the fugitive Alizarin Crimson he used straight from the tube to create the red velvet dress. So, no, it had nothing to do with zinc, but it is a cautionary tale about the tenuous stability of art materials.
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Clove Oil
Next up is Clove Oil. This essential oil is often a lifesaver for painters who need their paint to stay wet longer. Think of it as the coffee that keeps your paint awake and ready to party for days or weeks!
Clove oil is an anti-oxidant that is fantastic for slowing down oil paints’ oxidation (drying). Oil paints harden because the oil binder oxidizes and causes polymerization. A little clove oil in the paint can slow the drying, and a lot of clove oil will stop the paint from drying indefinitely.
To better understand the trouble clove oil can cause us painters, let me give a brief lesson on the drying capacity of different oils (skip a few paragraphs if you don’t like science and just want to know whether or not to use Clove Oil).
Here’s a question for you: Why can’t we use kitchen oils like Canola or Olive? Or, as one of our members asked, “Can I use walnut oil from a grocery store?”
Those are excellent questions; it took some digging to discover the answers.
The difference between oils in our kitchen and oils in paint is the Iodine Number (hereafter referred to as IN – an index of the number of double bonds present in the oil) and its effect on polymerization (the crosslinking of molecules that form oil skins).
Some oils have a naturally higher IN than others, and processing can also change the IN of some oils.
There are three types of oils: non-drying, semi-drying, and drying.
Non-drying oils have an Iodine Number of less than 125, semi-drying oils are between 125 and 150, and drying oils are over 150. (Don’t quote me on the numbers. The numbers I listed are from Wikipedia, but two other sources, Natural Pigments and a woodworking thread, list them differently. I will put the alternate numbers at the end of this topic. The point of the numbers is to give you an overall idea of how oils differ from each other).
The oils used as a binder for paint all have an IN greater than 150 when correctly processed.
Linseed oil has the highest IN of 170-204. Walnut’s IN is 132-162. Poppyseed’s IN is 140-158, and Safflower’s IN is 135-150.
Now you know why linseed oil dries more quickly than the other painting oils.
(As an aside: Perilla oil dries faster and harder than linseed and is used in paints and varnishes in Asian countries. Why don’t we use it for paint in the United States? I don’t know. We did this from 1939-1945 before the war interrupted the supply. Maybe it’s because it yellows more than linseed or is more expensive.)
Safflower oil is a semi-drying oil that dries very slowly, which is why it works well as a brush cleaner. If you see paints using Safflower or Poppy seed oil, be aware that they will take longer to dry unless something like an alkyd is added.
Kitchen oils are primarily non-drying because their IN is less than 125. Oxidation causes them to become rancid, but they do not polymerize like drying oils and form dry, hardened skins. Some non-drying oils like Canola can eventually form a skin, but the skin is much softer than the skin of drying oils.
Walnut oil has a wide IN range. Processing is what makes the difference. Kitchen-ready food-grade walnut oils are made with antioxidant additives to extend shelf life and slow rancidity. So, grocery store oils will not dry or form a protective skin like oil from art materials manufacturers. Art materials walnut oil and some woodworking walnut oils are refined with higher Iodine Numbers and are suitable for oil painting. The best way to determine which one you have is to mix your walnut oil with paint and test how long it takes to dry. You probably have a low IN oil if it takes more than a week or two to dry.
Phew, now that we’ve covered the science a bit let’s get back to clove oil.
Clove oil slows the drying time of oil paint because it contains eugenol, an aromatic oil that prevents the oxidation of vegetable oils. Aromatics are what we smell. They evaporate and lift into the air. The fumes alone are enough to rid the air of oxygen and slow the drying of oil paint.
I built a cover for my studio palette. When not painting, I dip Q-tips into a bottle of clove oil and place them under the cover (without touching any paint). Those clove oil-soaked cotton swabs keep my paints wet longer during extended durations between painting sessions.
Even though I don’t use clove oil directly in my paint, I’m beginning to reconsider using it at all.
Why?
I recently had a small area of a painting take weeks rather than days to dry. I had left the clove-oil-dipped Q-tips under the palette cover for a couple of weeks before I could resume painting. According to chemists, the clove oil fumes do not seem to penetrate the oil paint surface if kept under a lid for a night, but longer than that, they can potentially affect the drying time adversely.
Virgil Elliott had a similar experience: “For a short time, I used a Masterson palette with a cotton makeup application pad, placed in the center, to which four or five drops of clove oil had been applied. Due to illness, the Masterson palette stayed unopened, with the clove oil films building up, for about three weeks. After that, I laid in a background with a large proportion of flake white and a little black Roman earth added. The background passages stayed tacky for at least two months. I threw the painting out, not trusting the soundness of the paint film. Bottom line, I have firsthand experience of how exposure to clove oil fumes can backfire, even if no clove oil itself ever touches the paint.”
I can understand the allure of clove oil. Mixed with paint, it slows the drying, which can benefit us when we want to work alla prima (wet-into-wet painting), my favorite painting method.
But there’s a catch—it weakens the paint film, making it soft and easily damaged. The softer ‘skin’ allows dirt and pollutants to embed into the paint, and even the gentlest cleaning agents can damage the paintings. Acrylic paint and water-mixable oils dry with a softer skin, and when dust from the air settles onto acrylic paintings, it becomes irreparably trapped in the paint film. Conservators can’t remove the dust without damaging the painting.
Here’s a quote from a conservator on MITRA: “Every so often, we will encounter a painting by an artist known to have used clove oil or a painting that lists clove oil on the reverse as an ingredient in the paint. Many of these paintings have proven impossible to clean safely, meaning the yellowed, degraded varnishes used to coat the surface cannot be removed without causing irreversible damage to the paint layer. Clove oil is an attractive additive BECAUSE it hinders drying, but adding too much can create a film that remains sticky, does not form a cohesive, healthy paint film, and will remain sensitive to even the mildest solvents.
So, should you use clove oil or not?
I’m inclined to avoid it altogether. Then again, I’m not expecting my work to end up in a museum or need to have the varnish removed and the painting cleaned in my lifetime, which is when clove oil paint film softening becomes problematic (except on those rarer occasions when we see problems early on).
If you’ve been using clove oil in your paint and feel you can’t live without it, as long as you haven’t experienced noticeable problems, don’t stress over it. Keep doing what you’re doing. At least now you understand the potential pitfalls.
Iodine Values of Oils:
Almond, Sweet 95-109
Aloe Vera 105-120
Apricot Kernel 95-110
Avocado 75-95
Babassu 14-20
Baobab 55-95
Black Cumin 110-125
Blackcurrant 145-188
Borage 130-140
Brazil Nut 70-130
Camelina 127-160
Camellia 75-95
Canola 105-120
Castor 82-90
Cherry Kernel 90-115
Cottonseed 105-115
Cocoa Butter 30-45
Coconut 8-11
Corn 103-130
Cranberry Seed 140-180
Emu 75
Evening Primrose 140-160
Flax/Linseed 170-200
Grapeseed 130-145
Hazelnut 85-100
Hempseed 150-170
Illipe Butter 30-35
Jojoba 80-90
Kiwi Seed 170-205
Kokum Butter 30-50
Kukui Nut 130-165
Lard 43
Macadamia Nut 73-79
Mango Butter 40-55
Marula Oil 70-80
Mowrah Butter 53-70
Neem 65-85
Olive 79-95
Palm 48-58
Palm Kernel 14-24
Passion Fruit 125-140
Peach Kernel 95-115
Peanut 82-99
Pecan 108-118
Perilla 185-208
Pistachio 84-96
Poppyseed 130-144
Pumpkin Seed 115-140
Rice Bran 88-105
Rosehip Seed 180-195
Safflower 120-135
Sal Butter 35-43
Sesame 103-116
Shea Butter 45-65
Shea Oil 75-90
Soybean 125-145
Stearic Acid <3
Sunflower 120-145
Sunflower, High Oleic 80-100
Tallow 42-45
Walnut 120-140
Wheat Germ 115-140
Solvents
Solvents like Turpentine have been a staple of oil painting since Leonardo Da Vinci painted the Mona Lisa. That might be why we can’t figure out if she’s smiling or not – she’s a commentary on artists’ relationships with turpentine. We love the painting effects but hate the health-destroying downsides.
Artists use solvents such as Turpentine, Mineral Spirits, and Spike Oil to add fluidity to their paints or create watercolor-type washes to quickly cover their canvases. The solvent evaporates (dries) quickly (within minutes or hours) and can then be painted over without fear of substantially altering the initial wash.
The main problem with solvents is that their evaporative nature and aromatics are toxic and can, over time, cause severe health problems for artists. Turpentine is one of the worst, which is sad because it is the nicest solvent to paint with.
Turpentine has an oiliness to it that works beautifully with oil paints. When it dries, the colors retain their saturation and gloss. That’s partly because it evaporates at an even rate, avoiding the sinking/matte problem that odorless mineral spirits cause. Turpentine is also a non-petroleum product. It’s an essential oil made from pine resin, not from crude oil like mineral spirits.
Which demonstrates that the word ‘natural’ does not mean ‘healthy’.
Turpentine caused my painting professor to give up oil painting in his 60s. He started getting deathly ill every time he entered his studio. He thought it was oil paints overall, so he switched to watercolors shortly after I moved. I wish more had been known in the 80s about the toxic effects of solvents.
Turpentine is also absorbed through the skin and any dissolved pigments can be absorbed with it and enter the bloodstream. Turpentine potentially harms our lungs, eyes, kidneys, bladder, brain, and nervous system. I don’t know about you, but I’m thinking those are important to keep healthy if we want to keep painting.
Speaking of essential oils, spike oil has become popular, but I put it in the toxic category. The toxicity of Spike oil (lavender) is unknown—no actual studies have been conducted. My experience while painting with it is that it caused me to feel flushed and woozy (a technical, medical term), so I stopped using it.
It smells great (if you’re a fan of lavender), and in very small amounts, it might be fine, but with the amounts we often use as artists, the smell and the toxic effect are powerful. Although, it was nice to paint with. It dries more slowly than turpentine or mineral spirits.
Mineral spirits (especially Gamsol) are possibly the least toxic since they’ve removed more than 99% of the aromatics. Even so, it’s still toxic. I used it for almost 30 years without noticeable negative effects, which seems to be true with many artists. Some artists have developed strong allergic reactions over time. I decided to stop using it about 10 years ago to avoid potential problems. (As an aside – my professor used turpentine for several decades without any noticeable negative effects as well 😕)
The other downside is that we artists think we can mix a watery soup, and everything will be grand. All solvents, especially mineral spirits, weaken the paint film by diluting the binder (oil).
Matt Kinsey, on Mitra, had an excellent comparison:
“Imagine paint as analogous to a brick wall, with the pigment as bricks and the oil as mortar. Too much water in the mortar leads to lack of cohesiveness, weakly bound bricks and ultimately a failed wall. In paint, excessively thinned vehicle cannot maintain envelopment of the pigment, so there’s nothing to stick the particles together. When the solvent evaporates, there might be the same amount of materials, but just like a failed wall where all the bricks and mortar are still there, cohesiveness and orderly structure are lost.”
The degree of sinking-in of colors depends a lot on the primer/ground. Acrylic gesso is highly absorbent, so the thinned paint sinks more and dries matte rather than glossy. Oil grounds are less absorbent, so there will be less sinking-in.
In either case, you’ll want to be cautious. If you use too much solvent, the binder can become so separated from the pigment that the pigment has no protection.
I’m painfully familiar with that situation. I completed a 30×40 painting using generous initial color washes. When I finished, I varnished it with damar. A couple of weeks later, I decided it needed something more, so I took it outside and used turpentine to remove the varnish. I quickly got a ‘sinking’ feeling in my gut when I noticed that the areas where the color washes showed through were no longer there. The turpentine completely removed them. And, nope, I didn’t scrub or rub the varnish. I used a soft brush to apply the turpentine and let it do the work of dissolving the varnish. I then gently wiped it off, along with a generous portion of my painting.
Many mediums contain some type of solvent. Liquin, the most popular medium, contains mineral spirits. Others, like Canadian Balsam, contain turpentine. Be aware of the possible health effects.
So, let’s sum up the pros and cons:
Benefits of Using Solvents
- Improved Flow and Blending:
- Reason: Solvents like turpentine and mineral spirits reduce the viscosity of oil paints, making them thinner and easier to apply. This facilitates smoother brushwork and underpainting color washes.
- Faster Drying Times:
- Reason: Solvents accelerate drying by promoting the oxidation of the paint’s chemicals. They help the paint dry faster by breaking down the oil binder and allowing it to harden more quickly. As a result, washes created with turpentine can dry anywhere from a few minutes to a few hours. Mineral spirits-diluted oil paints take longer but are usually touch-dry in minutes or as long as eight hours.
- Cleaning Brushes:
- Reason: Solvents help quickly remove paint from your brushes, ensuring that pigments do not dry and harden in the bristles. This prolongs the life of brushes and maintains their performance. Turpentine is more efficient than mineral spirits at removing paint, but it’s also more expensive and toxic.
Downsides of Using Solvents
- Health Hazards:
- Reason: Many solvents emit volatile organic compounds (VOCs), which can be harmful when inhaled. Prolonged exposure can lead to respiratory issues, skin irritation, and neurological effects.
- Turpentine is absorbed through the skin, but mineral spirits are not.
- Plein air painters: The remarkable ventilation of outdoor painting makes the use of turpentine more tempting. If you choose to use it, make sure you wear gloves. You don’t want either the turpentine or the pigments in your bloodstream! Also, paint upwind – even outdoors, the fumes can accumulate and hurt your lungs and nervous system.
- Potential for Paint Deterioration:
- Reason: Overusing solvents can break down paint’s oil binder, weaken paint films, and cause potential issues with paint adhesion and durability over time.
Balancing the Use of Solvents
To mitigate the downsides while benefiting from the advantages, artists can take several steps:
- Use Odorless and Less Toxic Solvents: Options like odorless mineral spirits (OMS) are less harmful than traditional turpentine, but they are still toxic. Some artists develop respiratory allergies and rashes.
- Ensure Proper Ventilation: Working in well-ventilated spaces or using fume extractors can reduce inhalation risks.
- Limit Exposure: Minimizing solvent and opting for safer alternatives can reduce health risks.
- Safe Disposal Practices: Following guidelines for the disposal of hazardous materials can mitigate environmental impacts.
- Used mineral spirits can be poured into a safe container and left to let the paint settle to the bottom. Once the pigment has settled, the mineral spirits can be reused.
- Turpentine degrades over time when exposed to air (oxygen).
- Turpentine is biodegradable, while mineral spirits are not (although that is not a signal to pour used turpentine out on your lawn. The paint pigments left in the turpentine are often toxic, especially to birds and fish).
While solvents like turpentine can be amazing painting partners for landscape oil painters, our health should come first,
What art materials do you avoid? Tell us about your art materials nightmare experiences, or how you navigate controversial painting supplies.
Stay Healthy and Happy painting!
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is retouch varnish safe to use? some people endorse it, others not.
Im not an expert on any of the chemicals that clutter my studio but I have used retouch varnish for many years. It really smells awful so Im always outside when I use it. I let it dry before bringing it back into the studio.
That’s a great question, Linda! In the past, I used Retouch varnish and would have said yes, but based on newer research I stopped using it. First, as James mentioned, the fumes are usually toxic. Second, conservators say the retouch varnish creates an unstable film between paint layers, especially if you ever try to remove a final varnish to clean a painting. The retouch varnish does not form a strong, flexible film like the oil in the paints and is easily damaged by solvents that do not affect the actual paint film.
So, what have you used for the last ten years?
Great question John! I’ve replaced Gamsol mostly with a little walnut oil or Rublev Walnut Oil Gel. Recently I began experimenting with watercolor when I want to play with underpainting washes. With watercolor, I can paint almost immediately over the top with oil paints. Then, once it’s all dry, I varnish over the whole painting with Gamvar which protects both the oil and watercolor paints.
What is the best product for cleaning brushes used for oil painting?
Check out this blog: https://www.masteroilpainting.com/clean-oil-paint-brushes-with-turpenoid-natural/
I did some checking about using watercolor for underpainting as I was interested in using it. It was not recommended as it contains gum Arabic or other preservers.
What is the difference between walnut oil medium and walnut oil alkyd and when would you use each?
The alkyd version dries faster than regular walnut oil. I haven’t used the alkyd so can’t comment on when to use it instead of walnut oil but presumably if you want faster drying time.
Typing error should read “dries faster”
I use Vaseline to clean my oil painting brushes on the advice of a well known oil painter.
Hi Marion,
Vaseline is not a drying oil like Linseed or Walnut oil. If you use it because it is convenient and works well for you, I would recommend you clean your brushes thoroughly with soap and water. Vaseline is a petroleum product and not compatible with oil paints as far as the actual painting process is concerned. An excellent product I’ve been using for 30 years is Turpenoid Natural. I describe how I use it to clean my brushes in a blog post here: https://www.masteroilpainting.com/clean-oil-paint-brushes-with-turpenoid-natural/ – when the paint is extra dried on the brushes I soak the brush in the Turpenoid Natural for a couple of hours. To clean my brushes I dip the brush in the solvent and then work the paint out on my palette. Once it’s clean I use a paper towel to squeeze out as much Turpenoid Natural as possible and then the brush is ready to use. The tiny amount left in the brush will not damage or cause problems with the paint drying.