I recently bought some watercolour postcards through the SAA catalogue. Please can you tell me if there is a way to protect the surface of them once they have been painted, so that they can then be sent through the post?

June Crawshaw replies: To protect watercolour postcards against rain and moisture, which could smudge the paint, a spray sealer, watercolour or gouache varnish, or low-tack masking film should do the trick.