Elizabeth Cay (1771–1831), the grandmother of the Scottish physicist James Clerk Maxwell (1831–1879), was a talented amateur pastellist; several of her pastel portraits survive as does her set of pastels. She studied with Archibald Skirving (1749–1819), a Scottish miniature painter who later in life turned to larger-scale portraiture in pastel and served as drawing master to the Edinburgh elite. Cay's pastels are not fabricated sticks but consist of powdered pigment housed in various glass and ceramic containers and were apparently applied by stumps, still in her workbox, or brushes. The Cay color samples were identified by spectrographic analysis, polarized light microscopy, and microchemical tests which, in addition, indicated that a number of pigment mixtures present gave specific hues in keeping with earlier treatise accounts of the preparation of a pastel gamut for practical use. Elizabeth Cay's pastel workbox may be rare surviving evidence of one way, more common that we appreciate today, in which amateurs, and perhaps professionals, practiced pastel painting.