It usually comes from dirty rinse water, mixing too many colors together, or going back over paint while it’s half dry. Change your water as soon as it turns cloudy, mix no more than two or three colors at a time, and paint each stroke once before letting it dry. Watercolor also dries lighter, so mix your paint a little stronger than the shade you want.

The paper has lost its shine and no longer feels cool when you touch it with the back of your hand. If it still feels cool, it’s damp inside, so wait a few more minutes.

Leave the paper white for large bright areas like a snowy roof or glowing windows, because white paper keeps watercolor at its clearest and brightest. Save white paint (acrylic or gouache) for small final details, like falling snow.

For large areas, your brush should be wet enough for the paint to flow evenly without dripping. For small details, blot some water onto a paper towel so your lines stay crisp. A brush that’s too wet causes blooms and buckled paper.

A bloom happens when water from your brush touches an area that’s half dry and pushes the paint outward. Either work while the area is evenly wet or wait until it’s completely dry, and avoid touching it in between.