“Your water pot should never have any brushes sitting in it.”
This great advice came to me from a painting teacher I respect and it took a while to get out of the habit of using the water pot like I always had before. But it is such a good rule that now I give the same advice. The practice is easier to do if you are a watercolour painter, more difficult if you are trying to keep acrylic paint from drying in your bristles.
The most important thing I can think of when it comes to watercolour and acrylic brushes is to never (really, never) let go of your brush in the water pot. You should get away from the idea that it is a place to put your brush. It is not. It is a place to rinse your brush and pick up water, and then if you wish to let go of your brush you should lay it on the table or your palette. An old facecloth works well to protect the table. (I actually use two water pots, one for rinsing dirty brushes and one for clean water to pick up and mix with the paint.)
Ruining a nice point-
It takes just 5 seconds to ruin the point of a round brush and natural hair, the most expensive kind, is the easiest to ruin. Letting it sit on its point curls the tip to one side and in my experience it takes a lot of re-forming with your fingers, over and over again, and it usually will never be right again.
A curved tip on a round brush is aggravating. It is very hard to control because you are either trying to paint up to an edge with a curved-under hook that then flips up and changes position or with the middle of the hairs because the tip is curved up in the air.
I have been advised by one of our brush makers that you can often re-shape brush hair with a blow dryer.
Cracking paint on the handle-
My springy synthetic flats don’t seem to be affected in the bristles but the handles are just painted wood and sitting in the water can cause the wood to swell and the paint to crack and then flake off. This cracking handle can happen in just a few minutes n the water. So it is a good idea to treat your brushes well and not let any of them sit in the water.
A natural quill can rot-
Natural quill brushes, a squirrel mop for example, are all susceptible to the quill rotting if it is left in the water. A quill is a natural material, the base of a large feather that is split and used as a ferrule. There are brushes made with synthetic quill, these will not be as vulnerable to rotting in water. But if you never let go of your brush in the water pot you will never have to worry about this.
Since we learned as children to store our brushes in the water pot it is a lifetime habit to break. But you will find it is worth the effort. Your brushes will last a long time if you look after them.