In the late 18th century a new sister art and rival to miniature portraits appeared. Since about 1700 miniaturists had worked on ivory, and before that on vellum (animal skin). Up to the late 18th century, watercolour was used mainly by topographic artists, who applied it on paper to tint their drawings. But as watercolour painting developed as an art in its own right, miniaturists saw that working on paper was easier, and so quicker and cheaper. They could thus attract new patrons. Many now widened their repertoire and developed types of watercolour portraits on paper or card. They produced elegant graphite drawings, either tinted lightly with a watercolour wash or with the sitter's head painted minutely in watercolour.

This portrait by William Sherlock goes further and is finished completely in watercolour on card. But the drawback with working on paper or card is that they can both quickly discolour and degrade. This does not happen with the more expensive vellum or ivory.