The word 'miniature' is used to describe a technique of painting in watercolour, rather than a picture's size. Miniature painting developed as a separate art in the 16th century. In England, it became predominantly a portrait art. On the continent of Europe, however, the taste for portraits small enough to be carried on the person was often met by artists working within very different traditions. One type of 'miniature' (as all such small works are now known) produced more on the Continent than in England was the oil miniature. These were usually painted on metal. This one is painted on copper. Most of these oil miniatures are anonymous, since the art of painting small portraits in oil on metal was not one in which leading artists specialised. More often it was part of a repertoire of portrait styles offered by less well-known oil painters. In the Netherlands this medium was particularly common. One problem with oil miniatures is that the varnish often discolours, which results in a darkened effect. This probably became apparent quite quickly.