On Wed, 18 May 2011 21:34:30 +0100, David J
wrote:

Does anyone know what (apart from their own thinners) will clean a
paint brush that has been used with Hammerite paint?

It seems to defy everything I try!

It depends on the age of the paint. Original Hammerite used
1.1.1-Trichloroethane (Genklene). The modern formulation uses a
mixture of predominately Acetone and the petroleum distillate Naptha
(lighter fluid, Coleman fuel).