What is the best way to clean a brush after varnishing a painting? I usually rinse it out in white spirit and then dry it on a piece of kitchen towel, but the next morning the bristles are stiff with the residue of the varnish. I always use the varnish undiluted.

E John Robinson replies: To clean your brushes, wash them first in the white spirit and then with soap and water - put some soap in the palm of your hand and rub the brush into it under running cold water. Always thoroughly rinse brushes in a cloth soaked with linseed oil to prevent them drying out. It might be advisable to keep a separate brush purely for varnishing your work - that way, you won't risk ruining your favourite brush.