Pastels have an illustrious history. Renaissance artists from Barocci to Leonardo used them and Jean-Etienne Liotard mastered the medium, as shown in our current exhibition. But how have pastels evolved, and how do artists use them now?

What is a pastel?

A pastel is a stick of pure powdered pigment combined with a chemical binder. As a medium, it sits comfortably between drawing and painting, giving artists both a sketch-like fluidity of line and the rich iridescent colour of paint. But unlike paints, pastel colours are blended on the paper itself, and artists develop their own unique ways of doing this, using either their fingertips or a cloth, perhaps even a little water. Jean-Etienne Liotard achieved a staggering level of detail and tonal subtlety in his pastels. He would have had no more than 25 colours available to him, which he could lighten or deepen by adding plaster of Paris chalk to the base (a combination of pigment and Arabic gum).

How have they changed?

By the 19th century, pastels were bound with oil and wax, making them less crumbly and able to stick better onto the paper. But it was the introduction of chemical-based dyes which revolutionised the medium. Artists had dozens of colours at their fingertips, including intense and unusual colours like fluorescent green and salmon pink.

Artists including Edgar Degas and Edvard Munch explored the new sophistication of the medium. Degas – who initially used pastels for sketch portraits but embraced the medium by the 1880s – used fixatives to experiment with building up layers of colour in his work. In The Tub (1886) he achieved a woven surface of colour, capturing the woman’s movement and the translucent surface of the water. For Munch, too, pastel allowed experimentation with the vividness of colour. Of the four versions of The Scream completed by Munch between 1893 and 1910, it is the one made in pastel which is the most vivid.

Pastel remains a popular medium today. Here are some top tips from Royal Academicians who use pastels in their work.

Jean-Etienne Liotard is in the Sackler Wing until 31 January 2015.
Ann Christopher: Drawing – The Lines of Time will be in the Tennant Gallery from 25 February 2016.