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I'm working on a new painting and prepared the canvas with several thin layers of acrylic paint to create a solid black background which I then let dry for a couple of days. I then began painting over it with oils. Five days after applying the acrylic layer, I was removing a bit of the oil paint using oil of spike lavender which quite unexpectedly also removed much of the underlying acrylic paint. The acrylic layer is now a bit tacky in that spot and some of the oil paint has gotten mixed into it.

Can I safely continue to paint/mix the oil paint over and into this acrylic/oil combo? Or should I do my best to scrape off all the paint from the compromised area before painting over it?

I know you can't paint acrylics over oils as the acrylic layer will crack and you can't mix them due to the evaporation vs polymerization mechanisms of the different paints, but technically the acrylic paint was dry. The solvent caused it to break down, but there should be a negligible amount of actual water in the paint itself. Since the acrylic paints (when dry) seem to just be polymerized -acrylates and "dry" oil paints are polymerized fatty acids, would mixing a water-free acrylic paint with oil paints using a non-water solvent be roughly equivalent to (somehow) mixing cured oil paint with wet oils?

And moreover, will this lead to excessive cracking?

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    What is "water-free" acrylic paint? All the acrylics I have seen are water based. So you would not be mixing cured oil with wet oil, you'd be mixing oil and water or trying to anyway. Are you talking about Alkyds?
    – rebusB
    Commented Oct 19, 2023 at 14:18
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    Also curious about that base coat. The lavender oil should not have dissolved it after a few days of drying if it was acrylic paint. Was the original ground that the black acrylics went on painted with something oil based?
    – rebusB
    Commented Oct 19, 2023 at 14:26
  • @rebusB I was using the term "water-free" to describe the acrylic paint that has fully dried and then been chemically broken down with a non-water solvent. Regarding the base coat - I used Liquitex acrylic gesso on PVA sized canvas which had fully(?) cured for about 3 months. Lavender oil (and even the fumes) will definitely break down pretty much any type of plastic if left in sufficiently high concentration for an extended period.
    – asdf
    Commented Oct 20, 2023 at 16:11
  • This problem may be more about erasing the paint with a strong oil based solvent than painting a layer of oil paint over acrylic.
    – rebusB
    Commented May 20 at 21:45

2 Answers 2

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Generally you can paint oils on top of acrylics, the oils should hold on to the acrylic paint fine unless it is too glossy to get a purchase. After all most gessos that make the foundation of oil paintings are acrylic based. The binding materials are not incompatible in that direction. But the acrylic paint, just like any paint, will be vulnerable to agressive application of oil based solvents.

In this case the problem may lay with the PVA sizing. Sizing traditionally was used before applying an oil based ground to a canvas to protect the fibers from being broken down by the oil and its solvents. Acrylic (water) based gessos do not have this risk. If anything using the PVA may lead to the gesso not adhering to the canvas very well and could certainly be why it is coming up so easily with the spike oil penetrating it.

I have not used spike oil in the past but did get some to see what it does to acrylic paint and it does turn it into a weird oily rubbery substance, but it took full saturation with the solvent and day to break down. I have never had any issues with canvases that were acrylic gessoed and then heavily worked over with turpentine and mineral spirits when applying and removing layers of oil paints.

Also, you can get black gesso which would be more durable than black acrylic over regular gesso. Using that without the PVA may give you a much more stable ground to work over in oil paints as you see fit, and possibly even stand up well with the PVA underneath it.

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No, acrylic color can't be mixed with oil paint. If it is not possible to remove the oil color, then you should continue with the oil color from there. If the underlying acrylic paint is removed, don't worry, let it fully dry. Then you can use oil color directly over there.

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  • The problem is that the acrylic paint became tacky, and mixed with some of the oil paint. I also would advise against leaving out the primer/ground if the rest of the painting has it: that can yield new problems, and will likely influence the end result.
    – Joachim
    Commented May 20 at 7:51

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