Tips for Keeping Acrylics From Drying While Plein Air Painting

Artist's plein air easel set up in a field.
An artist's plein air easel set up in a canola field. Roberta Murray/Uncommon Depth/Getty Images

There are advantages and disadvantages to painting with acrylics en plein air (outside), primarily having to do with its drying time.  One of the benefits of acrylic paint is that it dries so quickly that, unlike oil painting en plein air, you generally don't have to figure out how to carry wet paintings home. On the other hand, particularly when painting outside during the hot days of summer, it can be a challenge to keep the paint from drying too quickly, both on the palette and on the painting, itself.

What is Acrylic Paint and Why Does it Dry Fast?

Acrylic paint consists of pigment suspended in a binder of acrylic polymer emulsion. Water is the vehicle for the acrylic polymer emulsion and is forced out and evaporates as the paint dries.  As this happens the binder locks the pigment in place, and the paint forms a film on the surface, called skinning. This first of two drying stages is called "dry to the touch." This happens very quickly, and even more quickly in a hot, dry environment. 

The second stage of drying is when the complete layer of paint dries, and, according to Golden Paints, depending on the thickness of the layer, can take from a few days to even months or years for very thick layers of 1/4" or more.(1) 

Water is also the solvent for acrylic paint. When you add a bit of water to wet acrylic paint, it releases the binder and allows the paint to flow more smoothly. Too much water, though, breaks down the chemical composition, causing the paint to bead and pigment to separate.

Tips

Here are some tips for how to transport your paints, keep them workable and prevent them from drying out too quickly so you can enjoy the benefits of plein air painting in acrylics.

  • Always bring along and use a water mister or atomizer. Using a fine spray, spray the paint on your palette periodically to keep it from skinning. This is when the paint develops a solid dry thin layer on the surface under which the paint is still soft. If you disregard this skin and attempt to continue to load your brush with the paint, you will get annoying flakes of dry paint on your brush and ultimately on your painting. A fine mist will keep the paint workable without affecting its viscosity or opacity.
  • Use a stay-wet palette such as the Masterson Sta-Wet Premium Palette (Buy from Amazon). This palette consists of a cellulose sponge that, when moistened and inserted beneath special palette paper, keeps paint workable for hours when the lid is off, and for a week or more when the lid is closed. The Sta-Wet brand palette paper, Sta-Wet "Pro-Palette" Acrylic Paper (Buy from Amazon), is permeable, cleanable, and reusable. This airtight box is perfect for transporting your wet paints.
  • The Mijello Artelier Airtight Peel-Off Artist Palette (Buy from Amazon) also keeps acrylic paints wet for weeks. If it does dry on the palette it is easy to peel the paint right off. 
  • Use professional grade paints rather than student grade paints. Professional grade paints have a higher pigment to binder ratio and tend to stay wet a bit longer than student grade. According to Winsor & Newton"Professional Acrylic colours remain usable on the palette for slightly longer than many other acrylics. This working time has been increased by 20% compared to the previous artist quality Winsor & Newton range; Finity.  A longer working time allows artists to have less waste on the palette as well as a longer time on the canvas for blending as colours will remain workable on the palette for over 30mins."(2)
  • Make sure to prime your support (the surface on which you are painting) well or paint it with an underpainting of acrylic paint so that it absorbs less moisture from your painting. Although you can paint on unprimed paper with acrylic, when painting plein air you don't want to work on an absorbent surface such as unprimed watercolor paper.
  • Always carry an umbrella you can set up to block the sun (or the rain) and protect the paints and your painting from direct sunlight. The Guerrilla Painter Shadebuddy Umbrella (Buy from Amazon) is easy to use, stable, and adjustable. 
  • Don't work in direct sunlight. Keep your painting and your paints out of direct sunlight. Work in the shade or under an umbrella.  
  • Try to keep your paints cool (but above freezing). You might want to keep a cooler in your car to store your paints when you are not using them; or keep your paints in a light-colored container that reflects the light or under a light-colored cloth. Do not keep your acrylic paints in a hot car. 
  • Develop a habit of working thoughtfully, decisively, and quickly when outside. Do compositional studies before beginning your painting. Prepare and prime your canvas ahead of time. Sketch in your composition and values on your support with soft pencil, charcoal, water-soluble pencil or crayon, or block in shapes and values with a thin glaze of paint.
  • Paint on small supports of 11"x14" or less so you can cover the surface easily and capture what is important in a reasonable amount of time. 
  • Bring several small supports and work on several paintings in one session.  Simplify your composition. Get the major features down and capture the light. Don't feel that you have to capture every detail or finish the painting as you would in your studio.
  • There are a variety of different mediums that can be added to conventional acrylics to extend the drying time. Try Golden Acrylic Glazing Liquid (Buy from Amazon) if you work in thin layers, or Liquitex Slow Dri Blending Gel (Buy from Amazon).
  • Use an acrylic retarder, such as Golden Acrylic Retarder (Buy from Amazon). This is an additive, though, so you have to be careful not to use too much so that it doesn’t destroy the integrity of the paint.  Acrylic retarder and other mediums tend to make acrylic paint more translucent.
  • Remember to keep your brushes wet so the paint doesn't dry on them. Bring along wet paper towels in a ziploc plastic bag to store your used brushes until you can get home and clean them with soap and water. 
  • Try limiting your palette of colors (one or two of each primary, plus white and black) and squeeze out onto your palette only what you need. The less paint you use and have to mix, the more quickly you can paint and the less time your paint will be exposed to the drying effects of heat, sun, and air.
  • Alternatively, some artists have a palette of many colors that they squeeze out into the layered compartments  - one color per compartment - of a fishing tackle box. Misting the paint with water and closing the toolbox lid when not in use keeps the paint wet for weeks. 
  • Avoid painting during the middle and hottest part of the day when the sun is directly overhead and the strongest. The light is flatter and less interesting then, anyway. Instead, try to paint before 10:00 am or after 4:00 pm when it is cooler and the shadows are longer and more interesting. If you are an early riser or can paint near the end of the day, try painting at the Golden Hours - the hour just around sunrise and sunset - the photographer's favorite time,  when there is a golden glow cast on the world. You will have to paint quickly then, since the sun angle, light, and colors change rapidly.
  • There are several different brands of acrylic paint that have recently been developed that prolong the drying time. One of them is Golden Open Acrylics (Buy from Amazon). This is a professional line of acrylics and mediums from Golden paint manufacturer that are formulated to stay wet longer both on the palette and the painting, allowing for a variety of techniques that are typically more difficult with acrylics, such as blending and shading. Because you can continue working with the paint as long as is needed, there is less paint wasted.These paints can be reactivated when they have become tacky before they dry completely. You can also get Golden Open Acrylics Landscape Set (Buy from Amazon) that has a nice color palette for plein air painting. Golden Open Acrylic Mediums (Buy from Amazon) extend the painting time even further.  They come in matte, gloss, or gel and can also be used with regular acrylics to slow their drying time. Follow the manufacturer's instructions.
  • Chroma Atelier Interactive Acrylics (Buy from Amazon) is another acrylic paint that has recently been developed. Unlike open acrylics, interactive acrylics dry at the same rate as conventional acrylics and can be used in the same way. However, interactive acrylics can be reactivated with a mist of water from your water sprayer, the Atelier Fine Mist Water Sprayer (Buy from Amazon), when tacky or with a mist of Unlocking Formula when dry. It is best to use distilled water with the water sprayer if possible. Watch this painting demonstration of Chroma Atelier Interactive Acrylics from DickBlick and this Atelier Interactive Demonstration by Mitch Waite.
  • You can also mix these slower-drying paints and mediums with regular acrylics to extend the drying times of the regular acrylics somewhat, although the effects will not be the same as if you used the slower-drying paints by themselves. 
  • Especially if using conventional acrylics, be organized with your materials and set-up so that you don't waste valuable time looking for an item or getting something you forgot while your paints dry on your palette. 

Further Reading and Viewing

Common Misconceptions About Interactive

The Acrylic Drying Process, Golden Paints

How Fast Does Acrylic Paint Dry Once It's Out of the Tube?

Golden Open Acrylics 

Chroma: Tips for Plein Air Painting

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REFERENCES

1. Golden Paints, Technical Notes on Drying, http://www.goldenpaints.com/technicalinfo_drying, accessed 8/6/16

2. Winsor & Newton, Understanding the Drying Time for Acrylic Paints, http://www.winsornewton.com/na/discover/tips-and-techniques/acrylic-colour/drying-times-for-acrylic-paints-us, accessed 8/6/16

RESOURCES
Skalka, Michael, Questions Answered/Advice From Experts, Acrylic Artist Magazine, Summer 2016