New artists often have trouble understanding what watercolor mud is when we are talking about watercolor painting.

What it isn’t is the color of what we see in a puddle of wet dirt.

Mud, when talking about watercolor painting refers to a section of the painting which is not smooth and transparent looking. Instead, it looks dull and lifeless. If the paint is not allowed to flow on the paper, you will not see the colors softly merge with one another, which is one of watercolor’s beautiful qualities.

Understanding how watercolor mud is produced is the best way to avoid it.
Avoid creating watercolor mud with plenty of paint and water in your brush and quick light brush strokes

It is very easy to paint clean watercolor washes and you must work very hard to produce muddy ones – this is a bit of a clue as to how a muddy watercolor is produced.

First let us look at how to create a non-muddy watercolor wash.

Quick brush strokes with plenty of paint that flows down the paper, without fiddling.

Creating a muddy watercolor wash

Now let us try to create a muddy wash. The clue was in my earlier statement about fiddling.

In a clean wash, the paint is allowed to settle on the paper, and to dry before being disturbed.

In a muddy wash, the watercolor paint is kept moving around while nearly at the dry stage. This often happens when beginner artists mix insufficient paint and must try to mix more. All the while the painting surface is drying – at the damp stage. Another cause is when the student uses too small a brush and must make many more brush strokes than are needed.

The main reason watercolor mud is created is because you keep fiddling with your washes, while the paint is drying, you get to a point where there is no longer enough water on the surface of the paper to let the paint settle back down. Think of a small pool of water with fine sand on the bottom. While the sand is still covered with lots of water, no matter how you disturb the sand it will always settle back to a nice smooth surface. However, when the water has nearly evaporated and you are just left with damp sand, if you now disturb it, say with your foot, the sand will stay raised instead of falling back down into a smooth layer.

This raised surface does not let the light pass through it as uniformly as when you just do a one pass clean wash. These areas cast tiny shadows on the paper. Just like damp sand on a beach that has been disturbed by footprints, etc. All this contributes to the dull look of that passage.

The secret to clean washes is to first mix plenty of paint. While you are learning, I suggest mixing as much as you think you will need and then double the amount. Then test the mixture on a scrap piece of watercolor paper, to make sure the tone is right. Now you are ready to paint.

If you are painting a large area, use a big brush. If it is only a very small area, then a small brush should be ok. Practice and observation will show you just how big a brush you can use for a particular shape.

When doing a glaze – a wash over a dry earlier one, make sure the earlier wash is totally dry, including the paper, before you lightly lay down the glaze on top. Otherwise you risk creating watercolor mud.

Watercolor Mud Video

I have a on this topic on my YouTube Channel which helps explain this process further:

Watercolor mud and how to avoid it