This has just been brought to my attention by a few customers. Like Gold says above I had been turning a new style vikan oval brush sideways to get under the downstairs openers. I thought it was non-marking but obviously not. I don't think the grit I had picked up helped either. I've changed to a supalite brush now and try not to tilt the brush.upvc solvent cleaner does remove it as said. The stuff I had stinks of pear drops though and nearly knocks your head off. My van stinks. Do the supalites mark does anyone know?
The older vikan brushes had a red rubber rim all round them that left terrible red smears everywhere. We used to cut it off