How to paint a sunset Landscape
Use a big brush, something at least 1.5" or 3 cm wide, so you get the paint down rapidly (and can't try to paint details). Paint in long strokes, don't dab at small sections until you've created the overall effect of a sunset sky. Once you've got the overall impression of a sunset, then you work back into this to tighten up your cloud shapes if you wish.
Have the colors you want to use to hand. Depending on the sunset you've got in mind, you'll want a yellow, orange (or red and yellow), blue, purple (or blue and red), and white plus something that'll make dark shadows in the clouds such as burnt umber or Payne's Grey. The latter mixed in with your sunset colors work well for silhouettes in the foreground too.
Start by making the entire area where the sunset sky is going to be damp. This will help the colors you're going to be painting with spread easily and, with acrylics/watercolor, slow down the drying rate, giving you more working time. If you're using acrylic or watercolor, you can use clean water or liquid (fluid) white. If you're using oils, use a thin glaze of quite liquid white or a very thin wipe off the oil you use.
Work from light to dark, so you don't have to worry as much about getting your brush totally clean between colors. Also because it's easier to make a sunset darker than it is to lighten it. So start with the yellows and oranges, then add the darker colors.
If there are going to be any areas of blue, don't paint yellow or orange there -- if you do, you'll end up with a green mix when you add the blue.
Rather use too little of a dark color initially than too much, but if you do find the sunset has gone too dark, wipe off the paint with a cloth and start again.
Blend the colors so you've got mostly soft edges rather than hard edges. Even the edges of clouds tend to be surprisingly soft.
Don't forget to consider tone, not just color. Check the tone of the sky towards the top of the scene compared to the horizon. Watch for areas of light tone where the sun catches the edges of clouds (add a little white).
Any objects silhouetted in the foreground will be very dark in tone, but unlikely to be totally black and flat. Mix a chromatic black for silhouettes.
Once you've got the general feel of the sky working, then go in to refine the shapes of your clouds. Focus on the highlights and darkest areas rather than fussing with the middle tones.
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