dilute ammonia with a little detergent, maybe just a touch of alcohol with very warm water. rinse again with water.

most water base (non latex type) uses a carboxylated resin that is then treated with ammonia to replace the COOH with an NH3 which makes it water soluble. originally it will have ~10% cosolvent like butyl cellosolve (BC) with water but always maintaining the proper pH (basic not acidic)