Combining oils and acrylics in the same painting will allow you take advantage of the unique properties of each medium. Acrylics dry quickly so you can block in large areas of color and fix mistakes immediately. Oils dry much slower so they allow you to create smooth blends and soft edges with ease. However, you have to be careful with the order in which you apply them.
Can I paint acrylics over oils? No, painting acrylics over oils is not recommended by manufacturers or professional artists. The acrylic paint won’t adhere properly to the oil paint, and it may peel. You can successfully paint oils over acrylics but you shouldn’t use acrylics over oils.
Testing Acrylic Paints over Oils
Even though artists generally agree that you shouldn’t paint acrylics over oils, I couldn’t find any actual testing that proves it’s a bad practice. I decided that if I’m going to write an article on this topic that I should perform my own testing.
I designed this test to give the acrylic paint the best chance of adhering to the oil paint. Wood panels provide a more stable support than canvas because it doesn’t flex or stretch. When the canvas flexes, it stresses the paint film.
I chose to use hardboard for this experiment and I prepared it by sanding it to rough up the surface. Then I applied two coats of gesso and let it dry for over 24 hours.
When the gesso was dry I applied a thin coat of Winton Burnt Umber oil paint. According to Winsor and Newton, Umbers dry to the touch within two days. I allowed it to dry for four days.
Finally, I painted over the layer of oil paint with the acrylic colors listed below. The same pattern appears twice. I will allow the top portion to age naturally while I can use the bottom section for testing. After the acrylics cure, I will pick at the some of the colors on the bottom section to see if they will peel.
The rough surface of the hardboard shows through the layer of oil, so the acrylic does have some texture to adhere to. It will be interesting to see what happens, check back for updates. Feel free to leave your predictions in the comments below.
Below are the acrylic colors that I used for this test.
- Pyrrole Orange, Golden High Flow
- Titanium White, Golden High Flow
- Hansa Yellow Medium, Golden Fluid
- Napthol Red Light, Golden Fluid
- Light Green Permanent, Liquitex Soft Body
- Cobalt Teal, Liquitex Soft Body
- Pyrrole Red, Golden Heavy Body
- Quinacridone Crimson, Liquitex Heavy Body
Why You Shouldn’t Paint Acrylics over Oils
Adhesion Problems
The number one concern with painting acrylics over oils is that the acrylic paint won’t properly bond to the layer of oil paint beneath it. Below are the reasons I believe this is true.
Water and Oil Don’t Mix
Everybody understands that water and oil don’t mix. What this means for painters is that if you’re painting with a water-based medium such as acrylics, the surface you’re painting on should be free of grease and oils. This includes the oils from your skin and any skin care products such as hand lotions.
Artists may not be as strict about this as painters in other professions. For example, auto body repair shops degrease the exterior of the car before painting them. They understand that if they want the paint to bond properly, the body of the car has to be free of finger prints, grease, and debris. The same is true for other industrial painting processes.
The main point here is that oil or grease on the canvas can interfere with the adhesion of the acrylic paint to the canvas. Oil paint is made up of mostly linseed oil and pigment. So when you paint with acrylics over oils, you’re painting over a thick layer of linseed oil. This is worse than painting over a greasy fingerprint. The oil paint creates a solid barrier of oil between the acrylic paint and the canvas. The result is that none of the acrylic paint is in contact with the gessoed canvas.
I should also note that the way oil and water repel each other can affect the adhesion of oil paints too. You don’t want to paint oils over a layer of gesso that’s still damp. Wait for the gesso to dry completely before painting over it with oils. It takes 24-48 hours for gesso to dry. Any moisture in the canvas can interfere with the adhesion of the oil paint to the canvas.
Dry Oil Is Similar to Non Stick Cookware
An idea that came to mind when I was writing this article is that a layer of dry linseed oil is similar to the layer of baked on oil that’s commonly found on cookware.
Many chefs “season” their cast iron pans before they use them for the first time. Seasoning is a process of applying an oil to the pan and then baking it with high heat to dry it. The hardened oil protects the cast iron pan from air and moisture. It also creates a smooth surface that food is less likely to stick to.
Oil Paintings Take Years to Cure
An oil painting can become dry to the touch within days but it takes much longer for it to fully cure. The actual time it takes to dry completely depends upon a variety of factors, including the thickness of the paint.
It’s not a good idea to add a layer of acrylic over a layer of oil paint that’s still curing. The acrylic binder is a type of plastic so you’re adding a layer of plastic on top of oil paint that’s still drying. While acrylic paint doesn’t form a perfect seal, it’s still an extra layer that may interfere with how the oil paint cures.
There’s a range of opinions about how long it takes oil paints to dry. I think that’s because there’s a difference between paint that’s dry to the touch and paint that’s fully cured. According to The Smithsonian, oil paints are in a state of change for many years after they’re dry to the touch:
[blockquote cite=”The Smithsonian’s Museum Conservation Institute” type=”left”]”Beyond drying to the touch, (oil) paints are still very active chemically and the polymerization process that starts with the uptake of oxygen will still be active for years afterward, and even affect the physical properties of paint decades after the paint film was applied. Both the chemical and physical processes in paints go on for many years.”[/blockquote]
I’m not a chemist, but it doesn’t make sense to apply a layer of acrylic plastic over a material that takes years to cure.
Painting Acrylic over Oils Violates the Fat over Lean Principle
The “Fat over lean” principle that oil painters follow is built upon the idea that paint should dry from the bottom up. In other words, the layers of paint closest to the canvas should dry first so that it provides a solid foundation for each additional layer.
Acrylic paint will dry long before the oil paints. So if you were to paint acrylics over oils, the acrylics will cure long before the layer of oil paint underneath. This is a violation of the fat over lean principle.
The reason why this is important is that you don’t want the surface you’re painting on to shift or move after the top layer is dry. Any movement in the layers underneath can cause problems in the top layers of dry paint.
Oil Paint Dries to a Smooth Surface
Paint requires a surface with some texture to create in order for it to adhere properly to it. Slick surfaces such as glass are much more difficult to get paint to bond to because it’s so smooth. There’s not much texture for the paint to latch on to.
Dry oil paint is not as smooth as glass but it’s also not as absorbent or rough as gessoed canvas. Applying gesso to a canvas will provide an absorbent and slightly coarse surface that will allow the paint to stick to.
Can I Apply Gesso Over an Oil Painting?
Another reason why you may be wondering if you can paint acrylics over oils is because you’re considering painting over an old oil painting with gesso.
Most of the gesso on the market is acrylic based so you shouldn’t use it to paint over an oil painting.
Every artist has paintings that don’t work out. Painting over them is one way of dealing with them. This may seem like a good idea, but in my experience it’s easier to just start over on a fresh canvas.
You may be tempted to paint over it with white oil paint instead of gesso but that creates the following problems.
- You’ll have to apply it thick enough to cover over the previous painting
- It will take a long time for each coat to dry
- One coat probably won’t cover it well enough
- Dry oil paint doesn’t provide a good surface for drawing on
- Some of the White pigments used in oil paints are prone to cracking
Even if you’re painting with acrylics, I don’t recommend painting over old paintings with gesso because you’ll have to deal with the texture that’s leftover from the previous painting. It’s surprising how even thin applications of paint can create textures that will show through when you paint over them.
The texture of the canvas will also fill in a little bit with each coat of paint. I like to use the texture of the canvas for dry brushing effects. Once the canvas is filled in with paint you lose that texture.
A Note About Shellac Primer
One trick that housepainters use to paint latex over oil based house paint is to use a shellac primer. You can paint over the oil based house paint with the shellac primer. Then when the shellac primer dries it will accept latex or acrylic paint.
While this might work for painting the walls in your home, I don’t recommend using house painting materials for making fine art. Most house painting materials are expected to last a decade. Fine art paintings can last for centuries by using archival methods and materials.
Conclusion
Once you start painting over acrylics with oils, you’ll want to finish the painting with oils. You can’t switch back and forth as you work. It’s also important to make sure the acrylics are dry before painting over them with oils.
As long as you stick to these principles, you can take advantage of using oils and acrylics in the same painting. Many artists use acrylics to quickly block in the painting and then switch to oils to put in the final details.
You may feel like you can ignore this advice if you’re working on practice paintings. However, it’s not a good habit to get into. I recommend spending your time mastering techniques that are proven to be sound.
