'Salem' (a portrait of Siân Owen, Ty'n-y-fawnog), is Sydney Curnow Vosper's most famous work. The finished painting was bought by William Heskith Lever for the Lady Lever Art Gallery, and was subsequently reproduced in the publicity for Sunlight Soap. The painting's considerable popularity, particularly within the industrial communities of south Wales, has been attributed to the nostalgia it evoked for a rural way of life which was rapidly disappearing.

Another interesting feature of the finished painting is the old lady's shawl which is said to conceal a devil's head within its paisley pattern. Some have argued that the caricature of the devil was an attempt to portray the vanity and hypocrisy of some Nonconformists. The artist himself, however, denied that this was ever deliberate.