After a few hours of painting, paint can work its way up into the bristles covered by the steel ferrule. If you don't clean the paint out of there, it will build up and cause your brush to get stiff and misshapen. After you comb all the paint out of the bristles, run water down into the brush. Finally, straighten out the bristles with a comb before you put the brush away. Protect the bristles by storing the brush in the package it came in.