Your brushes are a huge investment, so you want to be able to care for them properly to keep them around for as long as possible. Nina Weiss talks about what you can do daily to keep your acrylic brushes in top shape.
She shows a couple new brushes and points out that they are crisp with sharp edges, but as a brush ages, it splays and the tips are not crisp anymore. This is normal, but there are some practices to extend their life.
Never leave your brushes face-down overnight or even temporarily. Wiping and rinsing out the paint while you work, then storing them either on a flat surface or in your hand is preferable. Then, for longer storage they can be stored brush-side up in a jar. When traveling, there are different options you can get for brush holders that will protect the tips of the brushes and will help keep them in good shape.
Never, never, never allow paint to dry in your brushes. Don’t ruin good brushes by neglecting your cleaning routine.
Nina discusses her own cleaning routine by washing her brushes with Naptha laundry soap and Murphy’s Oil Soap and water that she has in a Tupperware container. She demonstrates how to work the soap through the bristles and lets them dry brush-side up. There is also a product called brush shaper that reshapes the brushes after cleaning to help get that straight edge again.
Nina keeps many brushes on hand in various stages of deterioration because they are still usable until paint is too built-up in the bristles. Acrylic paint dries very hard, so eventually the brush will become unusable, especially without regular cleaning.
In summary: never store bristle-side down; wash; and reshape to get the most out of your brushes.