Gold leaf

#C9A227Formula AuEarliest recorded use c. 2500 BCE

8 eras8 artists8 colors

Not a pigment but a metal, beaten thinner than anything else humans make by hand — a sheet of gold leaf is around a ten-thousandth of a millimetre thick, and a single gram covers half a square metre. In medieval painting it is not a colour but light itself.

Origin

Gold is beaten between sheets of parchment or, traditionally, goldbeater's skin made from ox intestine, in a process of repeated stacking and hammering that can take a day and reduces a coin to hundreds of leaves. The craft is ancient and essentially unchanged; Egyptian gilding survives from the third millennium BCE. For panel painting the leaf is laid over bole, a fine red clay mixed with glue, which gives a soft cushion for burnishing and lends the gold its warm tone — the reddish glow through worn medieval gilding is the bole showing. Shell gold, ground gold leaf mixed with a binder and used as a paint, was the alternative for fine detail and cost considerably more per area.

In art history

Gold ground is the defining feature of Byzantine, medieval and early Italian panel painting, and its meaning is theological before it is decorative: a gold background is not a place, it is the absence of place, an uncreated light against which sacred figures appear outside of time and space. This is why the shift to painted landscape backgrounds in the fifteenth century is one of the genuine revolutions in Western art — it moves the sacred into the world. It appears in four eras of this atlas. Gold also carried literal value: contracts specified the number of leaves as they specified the ounces of ultramarine, and the gilding was often the most expensive component of an altarpiece.

In the studio

Water gilding, the traditional method, applies leaf to a wetted bole ground and then burnishes it with an agate stone until it is mirror-bright; it can be tooled, punched and incised, and the raised patterns catch candlelight, which is what these surfaces were designed for and what they lose entirely under gallery lighting. Oil gilding, applied over a slow-drying size, is simpler, more durable and cannot be burnished, so it stays matte. Gold does not tarnish, oxidise or fade — it is the most permanent material in the history of art — but the leaf is so thin that it wears through with handling and cleaning, which is why medieval panels show the red bole at every edge and high point.

Afterlife

Still made the same way, still used in conservation, icon painting, architecture, bookbinding and signwriting. Substitutes exist — brass leaf, sold as Dutch metal, and various bronze powders — and they tarnish, which is exactly the difference. The revival of gold ground in Klimt and in a strand of twentieth-century painting is a deliberate archaism, quoting the sacred convention rather than continuing it.