With the ever rising cost of art and craft items like paint brushes, it is wise to be sure they are well cared for. The best way to do this, is too be sure they are properly cleaned and dried before putting them away.
Never leave brushes soaking in water. This can cause the bristles, which are generally the most expensive part of the brush, to bend, warp, separate, or fray. Over prolonged periods, the water can even damage the glues that hold your brush together. This can lead not only to bristles falling out, but to the entire ferrule (the conical metal piece that holds bristles in, and attaches them to the handle) coming apart from the handle, and make the brush completely unusable, unless repaired.
Always clean your brushes immediately after each use. This ensures that they do don’t suffer any of the water damage mentioned above. Some paints do not even mix well with water, so you must know this before cleaning them as well. However, most craft painters, and many artists as well, use primarily acrylics or watercolors.
Both of these are water-soluble, as are tempera paints, poster paints, and some forms of water-based enamels. Brushes used with these types of paints usually clean up easily with water, and a mild soap, if needed. Oil based, enamel based, and lacquer based paints require different chemicals for cleaning. They will not be dealt with in this article.
If regular cleaning does not take all of the paint out of the bristles, or if it has dried too quickly, and set into the base of the bristles, a substance known as denatured alcohol can be purchased (at art, craft & hobby stores, and often at hardware stores and the painting department of other stores) that will loosen these hardened paints from the bristles.
Some brushes may require reshaping after use. If your round brushes have lost their point, or your square, angled, or filbert brushes have separated in anyway, you can use water, or a bit of soap with water to reshape them. More exotic brushes, such as the fan shaped variety, must be swiftly brushed back and forth over toweling or cloth (I will admit, I often use my pant leg) before dry, or their bristles will separate, rendering them virtually useless for their intended purpose.
After cleaning, and reshaping if necessary, brushes should always be stored in an upright position in your brush container. If properly cleaned and stored after each use, good quality brushes can last a long time, perhaps even a lifetime. I have had some of my own brushes for over 30 years, and they are still in relatively excellent condition.
Source : Over 30 years as an artist, crafts-person, and trainer of others in these fields as well.