The answer to that is complicated because you may be surprised by how long it truly takes oil paintings to dry. Dry to the touch is not dry! Which is where the confusion begins.
When the solvents (think turpentine and the modern substitutes for it) in the oil paint oxidize, it leaves the surface of the painting dry to the touch. It can take as little as 24 hours and as long as 12 days for oil paints to dry. A lot depends on the content of the pigment itself. Pigment can be made of man-made solids or nature made minerals and organic matter.
Drying time (to touch) varies on how these react to the binder in the oils in the paint itself, how it reacts to the surface of the painting, the humidity and temperature in the environment and a host of other factors.
A fully cured painting is when it is at its maximum hardness and the chemical processes are pretty much at conclusion. THAT can take from months to years. (Paint archivists and chemists will cringe at that overly general statement, but we don’t need to delve into the minutiae of chemistry here….not that I would understand it anyway). With the exception of the Gamblin product below, a painting should be fully cured before varnishing.
Modern additives to the paint (mediums) like Liquin, or Alkyd forms of paint and dryers can speed up drying time by up to 50%. However, use these as underpainting, not the last layers of paint, or cracking can occur.
You will want to plan on using drying additives at the early stages of the painting and finishing with a more oily paint without dryers on the top. Paint with oil only (straight out of the tube) will be flexible and be able to expand slightly with humidity and temperature changes.
The thinner layers underneath with dryers as an additive are going to be more rigid. Flexibility is important for a painting to survive years intact. You can imagine this process somewhat like homemade pudding.
As the top layers cools, it forms a harder layer which with the interior cooling and solidifying, creates crevices and cracks on the surface. YUK.
The mantra that artists use is : FAT OVER LEAN.
This merely means that each subsequent layer of oil paint should have more oil content than the earlier layers. So, start the underpainting thinned with solvent, then the next layers use paint straight out of the tube, and the last layers with perhaps a tad more oil mixed in or use a medium with oil in it.
If you want to use a glaze as the final layer, first ‘oil out’ the painting then apply the glaze so that all they layers of paint can bind together well.
If a painting is dry to the touch, artists often send it off to a client or gallery. Afterall, who has time to wait for up to 24 months before exhibiting or selling your work??
Commissions, deadlines and the necessity to survive financially dictate when a painting can be shipped out of the studio once it is dry to the touch.
The rule to follow is that the thicker the paint application, the longer it takes to dry.
Very thick impasto paint strokes may take up to two years to fully cure and be ready for varnishing. Oil paints applied very thinly or with a medium additive can be dry in as little as two days.
I wish it was more dialed down with time tables and formulas to follow, but unfortunately, it comes down to generalizations and a lot of variables.
Most artists use their best judgement balanced with necessity.
How Long Does It Take Oil Paint To Dry On Wood Or Metal?
On a properly prepared wood or metal surface, oil paint will dry the same as on canvas. However, you would not want to paint on plain wood or metal without good surface preparation and a sealer and primer coat of gesso first.
Artist oil paint on untreated wood will react to the wood and over time, the wood will start to rot and deteriorate. Not only that, but the grains of the wood and small imperfections like knots can rise up through the paint and be unsightly. I’ve also had wood boards treated with a clear sealer yellow my finished artwork within five years.
Wood needs a good tooth by sanding first and chemical sealer and at the very least a heavy coat or two or three of gesso acrylic paint before oils can be applied. That all takes time. Metal likewise takes more steps of preparation before you can begin oil painting.
Nowadays I opt to purchase commercially prepared boards. Many artists enjoy the rigidity of wood and there are many modern products to choose that fit the bill and will be archival. I won’t trust knock-off brands unless their company can provide archival laboratory testing so that it is not acidic, or reactionary over time. I really enjoy this brand. It is a top of the line art product with artist approval all over the globe. It is archival and pre painted with gesso and ready to go:
AMPERSAND ART SUPPLY AMGBS09 GESSOBORD 1/8 INCH FLAT 9X12
When should I varnish?
Once a painting is fully cured, it can be varnished. The advantages of varnishing are many. Firstly the objective is to protect the painting for the long term. Dust, bugs, humidity, carelessness, sun UV rays and pollutants in the air all contribute to the deterioration of artwork. Varnish done correctly can not only protect the painting, but with knowledge and care, can be removed without harming the work and then reapplied again.
(With the exception below from Gamblin). If varnish is applied too soon, it seals the air from getting to the interior layers of the paint and inhibits proper curing and creates a boat load of problems archivally down the road with mold, cracking, lifting and other disastrous effects.
Not to be left out is the impact that some forms of varnish can have on the final work itself.
Some pigments of paint ‘sink into’ the surface of the support and end up dull, matte and a few shades lighter than when the artist first applies wet oil paint. It can leave the painting looking blotchy and dull. Varnishing can bring back that initial wet lush look of freshly painted oil paint and even out the surface look so that it all has the same level of sheen, or matte.
I watched one of my teachers varnish a painting that he had given to a friend six years prior. He showed us the dramatic before and after as he applied the glossy varnish to the fully cured painting. It was astonishing!
The gasps of pleasure from all of us as we watched the varnish being applied and the color come alive in a new and vibrant way was very audible. After watching that demonstration, there is no question in my mind that if vibant, rich color is one of the goals of your painting, then varnish can really enhance the final look.
One of the bad characteristics of varnish is it’s yellowing tendency over the lifetime of the painting. Here is a small jar of medium that I used with Lindseed oil, OMS and Damar. Just look at how it’s yellowed in 5 years.
Good grief. Imagine this on a painting of white porcelain china, white tablecloth and white flowers.
The old masters used Damar Varnish (American spelling here) and it can yellow horribly. If you’ve ever been to an art museum, you’ve seen evidence of varnish yellowing on oil paintings.
Some of it has been restored by archival chemists, but many of them have not, or they are too fragile to remove the old varnish and survive.
I have abandoned ‘the old ways’ and started using a modern varnish and solvent by Gamblin Oil Company. This product was developed by Robert Gamblin of the Gamblin Oil Paint Company in conjunction with Rene de la Rie at the National Gallery of Art in Washington D.C. Both superb chemists, they collaborated to create a new varnish called Gamvar.
It is a modern non-yellowing varnish with a specific resin that is bound with a modern milder solvent called Gamsol (also by Gamblin). This unique, modern varnish can be applied as soon as the paint is firm….no need to wait until it is fully cured. Hooray!!!
Gamblin Gamvar Picture Varnish – 8.5oz Bottle
It is colorless, clear and archival and removable with Gamsol. Hooray for modern chemistry. Win. Win!
It comes in gloss, matte and satin
And here is the solvent I use to thin the paints and clean my brushes of oil paint:
Gamblin Gamsol Odorless Mineral Spirits Bottle, 4.2oz
If you choose to use a Damar type varnish, the bottom line is , let the painting cure up to six months for thinner paint applications before varnishing, and let it dry up to two years for thicker applied paint.
Whatever varnish method or products you choose to use, make sure you use studio safety practices for your health and use archival paints and supports, solvents and varnishes to help your creations last for generations.
Bonus Acrylic Painting Content:
If you enjoy oil painting, you may just enjoy acrylic painting too! I sure know I do.
Please also be sure to read my article about the 10 Most Asked Questions about Acrylic Painting. <<Must Read If You Are Interested In Acrylic Painting
In this article I cover the following 10 questions:
- Is Acrylic Paint Waterproof?
- Is Acrylic Paint Good On Wood?
- Can You Paint On Metal With Acrylics?
- Can You Mix Additives Into Acrylic Paint?
- Can You Use Acrylics Like Watercolor?
- Can Acrylics Be Thinned To Transparency?
- Can You Use Acrylics On Fabrics?
- Can You Use Acrylic Paint On Paper?
- Are Acrylics Non-Toxic?
- Are Acrylics Flammable?
I look forward to hearing your feedback as I have a passion for painting and have absolutely loved acrylic painting for my entire life! I hope this inspires you to pick up this amazing craft as well!!