Weather is an occupational hazard for plein air painters.
When you commit to painting regularly en plein air you will have to deal with changeable weather at some point. Like everything, weather effects are all beautiful in their own way, and each has a unique set of techniques to capture it well.
In this week's Plein Air Adventure class we all drove through rain to find fog waiting for us at Vinoy Park in Downtown St. Pete's. Fog is one of my favorite weather effects because everything has lost edges (soft focus, no real definition) and is lighter and bluer than it would normall be so color is softened, greyed and lighter.
With fog, you have humidity, and that will affect your paint and support. As a pastelist, I use #Ampersandart Pastelbord, so humidity isn't a problem. I only take out the pastels that I use so that they all don't get too moist. Watercolor is probably most affected by atmosphere in that paint won't dry as quickly so almost all of your painting will be wet into wet.
Capturing fog is different in different media. I usually start with a tone, the basic value of the fog which is often a "2" on a scale of 1 (light) to 5 (dark). In this painting, I used a very light sky blue. This color will then mix with every other color I lay on top of it, so I take that into account. Fog means high key (lighter values, little or no black) so I'm not worried about getting strong darks.
Most of the darks will be in the foreground, from the waterline forward. So I lay in these darks on top of the fog color, along with several values of tree color with the darkest in the foreground. Keep in mind that cool colors recede and warm colors come forward. The foreground should always be warmer and darker that the background, especially in fog.
Fog tends to grey the colors as well, so I like to juice it up and add a splash of warm here and there to create color harmony and balance to the painting. Hence the building in the background and the warm color in the dock and water.
If the fog is particularly thick, and you can practically taste the air, like it was here, I may add an extra layer of the sky blue underpainting ON TOP OF the finished piece. This is something you can only get away with in pastel. We call it "scumbling" which is what happens when you lightly drag one color on top of another. Since pastel is not wet paint, the two colors do not mix physically so you can still see both very clearly. This is a form of optical mixing.
You can get the same effect in oil or acrylic by glazing a thin layer of lighter paint over the finished product, but it would be hard to do in the same painting session. You may have to let it dry a bit first. Watercolorists would just sand off some color after the paint has dried, or just applied it with wet-into-wet techniques so that it wasn't very dark to begin with.
All in all, give me fog over snow any day! Hope this helps in your repertoire of plein air skills and get the opportunity to paint in the fog soon. Feel free to post any photos below of your own foggy works! Join me weekly in Weds. at 9am-noon for Plein Air Adventure class in Pinellas County. You are welcome to try out a class for free if you've never painted en plein air before!