A common question we get is “how long should I wait before applying my next application of acrylic?” Actually, in most cases one can apply multiple layers at any time as this is one of the unique properties of acrylic products. It really doesn’t matter in terms of final film formation and toughness. But in some special cases, and for some applications, it is important to understand at least a few of these limitations for best results. As this timeframe can vary due to environment and application, this article assumes a relative humidity range between 30–60%, and a temperature between 68-72 F. Also, that the acrylic products are evenly brushed layers.
One of these special situations is the application of GAC 100 and Gloss Medium when used as a size to either protect against Support Induced Discoloration (S.I.D.) in acrylic painting or protect substrates from oil penetration when oil painting. For these purposes it is important that each layer be clear and touch dry before additional sizing coats are applied.
To allow the sizing layers to form a tight film, we suggest overnight drying before the application of Gesso. This is important for acrylics because sizing traps water soluble impurities from migrating into further layers including Gesso.
As with mediums, Gesso also dries quickly. Allow the first coat of Gesso to dry for at least one hour to be sure it will not lift when the next layers are applied. The number of Gesso coats is optional for the acrylic painter; however the oil painter may wish to apply 3 or 4 coats, eliminating the need for sizing and avoiding oil strike-through to the canvas.
When painting with acrylics, one simply needs to wait long enough so the gesso doesn’t lift when doing their application.
However, allowing the Gesso to dry overnight facilitates drawing, sanding or doing detailed work. Oil painters should wait even longer. According to the GOLDEN Product Application Sheet, Preparing a Painting Support, Gesso should be allowed to dry for a minimum of 3 days for proper mechanical adhesion of the oils. Oil paints and oil painting solvents are hydrophobic (water-resistant). If too much water remains in the acrylic layers, there may not be optimal adhesion.
Between Coats of Standard Acrylics
Acrylic painters have few guidelines during paint application except ones that impede the work process or begin to lift semi-dried acrylic skins. The acrylic readily attaches to other acrylic paint films and dries quickly without issues. If Retarder is used in a mixture extra time should be allowed in order to not have partially dry paints lift. Gloss Glazing Liquid can easily take up to an hour to become touch dry, while OPEN Medium and OPEN Acrylics can take a full day to become touch dry.
Between Last Coat of Paint and the Isolation Coat?
When the artwork is complete, an Isolation Coat is suggested prior to varnishing. Thick paints might feel touch dry in less than an hour but take longer to become solid. Overnight drying reduces the chance of color lifting. The GOLDEN Varnish Application Guideline suggests to “Make sure paints are sufficiently dry. For acrylics and other water-based media, if the painting is composed of thin layers, waiting a day or two before applying the isolation layer, followed by another two days to a week before varnishing, is recommended. If there are thick, impasto areas of acrylic paint, wait a week or two before applying the isolating layer or varnish.”
Upon drying, inspect the isolation coat and if the sheen is uniformly glossy, move onto varnishing. If the dried coat is uneven, apply a second isolation coat.
Isolation coats should be allowed to dry for a minimum of one day before proceeding to varnish. A longer time frame is acceptable. However, if two weeks or greater has elapsed, we recommend wiping the surface with a soft, lint free damp rag in order to remove any surfactants and assure good adhesion with the varnish layer.
Timeframes between Varnish Coats
We recommend waiting a bare minimum of 4 to 6 hours between coats of brushed-applied varnish, but if time isn’t a critical factor, wait overnight. This is because varnishes are resoluble and a more cured varnish layer is slower to reactivate and facilitates an easier secondary application. Spray application allows for faster recoating. The GOLDEN Archival Varnish can be applied at a faster rate because sprayed coats are thinner than brushed ones. Since there is no direct brushing, there is less chance of disturbing the underlying layer.
If you have any questions, please contact us at 800-959-6543/607-847-6154 or [email protected]
Bibliography:
http://www.centralhtg.com/blog/managing-home-humidity-for-maximum-comfort
https://en.wikipedia.org/wiki/Room_temperature
http://www.goldenpaints.com/technicalinfo/technicalinfo_prepsupp
http://www.goldenpaints.com/technicalinfo/technicalinfo_openmeds
http://www.goldenpaints.com/technicalinfo/technicalinfo_varnapp1
https://justpaint.org/investigating-the-drying-process-of-acrylic-color-and-gel-medium/
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Good article. I would add that your points about waiting for acrylic to dry before applying oil paint are also relevant to urethane. Urethane paints will also trap that water in the acrylic layer, making it a little more difficult to obtain proper adhesion.
Much depends on the technique being used, however. Thin layers of acrylic on watercolor paper are an entirely different beast from airbrush on steel panel, medium layers of brush applied paint on canvas, or heavy impasto with a knife.
Artists should experiment with their materials, do test samples, leave them out in the sun, stress test them, etc. I am always shocked at the low level of technical knowledge and professionalism in the fine arts community, when compared with professional industrial painters (e.g., automotive, product manufacturing). It’s good that Golden is publishing this information, as artists are woefully behind when it comes to ensuring that their paintings are structurally stable.
Great points, James. I do more test paintings than actual paintings. Each test allows one to try “what if?” without fear of ruining a painting. Some artists, such as Jackie Battenfield, have made a career from turning their test methods into paintings.
– Mike
Very informative article. Thank you. I’ve been an exhibiting artist for twenty years. Excellent info!
You are most welcome, Steven.
– Mike Townsend