The age-old advice to wait at least six months before varnishing oil paintings is a good practice but one that many artists resist. And it is understandable why because when a painting is completed, it often needs to be delivered immediately for exhibit or into the customer’s hands.
The Big Sleep Before Varnishing
So, artists often tout the recommendation to wait until the painting is “touch dry.” For some, this may be a sufficient amount of time. This recommendation, however, assumes that all paintings are created under the same conditions. Of course, we know this is never the case since one painter paints on absorbent substrates, another on non-absorbent surfaces, another will use lead white, others will use slower-drying titanium white, many artists paint with impastos, and others with thin applications of paint.
A few manufacturers claim that their varnish can be applied much earlier, such as when the painting is “touch dry,” so many artists grab this idea and run with it thinking the moment the paint surface feels dry, they have a green light to varnish. However, even these manufacturers are a little more cautious by recommending testing the surface of the painting for sufficiently dry, such as with a “fingernail test.”
Somehow many artists believe there is something special inherent in these varnishes. One blogger writes :
All varnishes are permeable, so oxygen will diffuse into and through them, allowing the polymerization of oil paint underneath. All varnishes slow oxygen ingress into the paint film, delaying drying.
Waiting at least six months is still the best practice for many painters. Instead, an artist may use (with due caution) the test described below as a method to determine when the painting is ready to be varnished if she cannot wait the prescribed six months.
The “fingernail test” may be what some manufacturers had in mind for the test method for “Dry Hard Time” described in ASTM D1640 :
Variations of this test may be used but will also give different results. A problem with using a hard and sharp object such as a fingernail (in contrast to a flat thumb) is that it can give false results depending on the pressure exerted on the paint film.
Whereas the test described above may work in your case, always remember that some interpretation of the results is involved, often leading to different conclusions. The safest and best practice is to wait the prescribed amount of time—at least six months. But if you cannot do so, use the test method ASTM D1640, and good luck.
For more information on varnishing, please consult this article: Selecting the Right Varnish for Your Painting
Debra (2017) How To Varnish A Painting: The Easy Way. Red Palette Studio. August 17, 2017. View Online. Last accessed 15 March 2020.
ASTM (2018) D1640 Standard Test Methods for Drying, Curing, or Film Formation of Organic Coatings. American Society of Testing and Materials.
Frequently Asked Questions
What happens if you varnish an oil painting too early?
Varnishing an oil painting too early can lead to issues like discoloration, cracking, or an uneven gloss. It's important to ensure the paint is thoroughly dry to prevent these problems.
How long after oiling out can I varnish?
After oiling out, wait until the surface is thoroughly dry before varnishing, which usually takes several days to a week or more. However, please read the next answer regarding oiling out as a final layer in your oil painting.
Should I oil out my entire painting before varnishing?
It's not recommended to oil out the entire painting before varnishing. This may be contrary to popular opinion, but adding a layer of oil over an entire painting may lead to yellowing and darkening as the painting ages. As some may claim, oiling out does not necessarily ensure an even sheen and proper adhesion of the varnish. Cleaning the painting before varnishing is usually sufficient to ensure good adhesion of the varnish to the paint surface.
What happens if you don't varnish an oil painting?
Not varnishing an oil painting may leave it vulnerable to dust, dirt, and environmental factors, potentially affecting its longevity and appearance.
Should I varnish my oil painting matte or gloss?
The choice between matte or gloss varnish depends on the desired visual effect and the specifics of the artwork.
Can I varnish oil painting after a month?
Varnishing an oil painting after a month is possible if the paint is hard dry, but thicker layers may require more time to cure.
What is the best varnish for oil paint?
The best varnish for oil paint depends on factors like desired finish, painting style, and environmental conditions. Please read our article: Selecting the Right Varnish for Your Painting
Can I varnish my painting after a week?
Varnishing a painting after only a week is typically too soon, especially for oil paintings, which require longer drying times.