You'll need the following:
- A piece of watercolour paper stretched on a drawing board.
- A large brush (such as a number 10 or 12).
- A jar of clean water.
- An easel or something to prop your drawing board up at a 30-degree angle to the horizontal.
- A cloth for drying your brush.
How to Lay an Even, Flat Wash:
Step 1: Place your board at a 30-degree angle so that the brushstrokes you're going to put down will flow into each other. You're going to work from top to bottom. Load your brush with plenty of paint. Starting at the top edge of the piece of paper, put down a broad horizontal stroke, from one side to the other as if you were drawing a line with a pencil. Don't lift your brush until you're all the way across. Some paint will accumulate at the bottom of this stripe. Don't try to get rid of this, it's an essential part of a wash.
Step 2: Add some more paint to your brush, then make another horizontal stroke making sure that the tip of your brush picks up the "river" of paint at the bottom of the first stripe. Don't paint above this river or you'll ruin the evenness of your wash. Work quickly as you need to lay the next stroke before the river dries up, otherwise you'll end up with lines in your wash, and before it runs down the paper
Step 3: Continue in this way until you get to the bottom of the paper. Squeeze the excess paint from your brush between a fold of cloth, then use the brush tip to lift the excess paint from the last stroke. Don't worry if this makes the last stroke seem a little lighter than the rest, some of the paint will seep down while it dries and sort this out. Leave your board at an angle until the wash is completely dry, otherwise some of the wet paint will flow back up and your wash will dry unevenly.