Take a gold leaf out of gilder's book

Dunedin Public Art Gallery conservator Jenny Sherman with gilding tools at the gallery on Tuesday. Photo by Peter McIntosh.

Gold seems to have magical qualities - it's considered a noble metal, it doesn't tarnish and it often symbolises perfection, so it's no wonder it was used in medieval religious paintings to simulate heaven, says Jenny Sherman, paintings conservator at the Dunedin Public Art Gallery.

As part of the Dunedin Heritage Festival, on Sunday she will be demonstrating the art of gilding.

Gilding is the art of covering something with a layer of gold leaf that has been hammered to the thickness of a few atoms.

The technique of gilding on wood, such as in a painting or on a frame, has changed little since medieval times, and Sherman uses recipes from a 14th-century treatise by Cennino Cennini.

She prides herself that apart from the electric hot plate to heat the gesso, all her gilding tools could have been found in a medieval workshop.

She makes a gesso, a mix of powdered chalk and rabbit-skin glue, which forms a jelly-like liquid.

This is applied to the wood, then a bole, a red clay, is brushed on and allowed to dry. This compresses when you burnish it and gives a mirror-like surface, she says.

A thin layer of size (thin glue) is applied to the bole and a gold leaf is picked up from a suede gilder's cushion with a gilder's tip, a wide, thin, squirrel-hair brush, and placed in position.

The leaf is so fine it will disintegrate if you touch it with your fingers.

When it is dry, it is burnished with an agate tool which smooths out any wrinkles.

Gilded surfaces remain fragile and are easily abraded or damaged.

Gold leaf comes between pages in a little book about 9cm square.

When an item is gilded, the overlapping of the leaves is evident if you look closely.

When you restore an item you can never achieve perfection because you can never match the gold that was used, Sherman says.

Outdoor surfaces can also be gilded but a different method is used.

When Sherman lived in New York, Art Deco buildings and some of the sculptures in Central Park were being regilded.

When newly gilded they looked gaudy and shiny until grime settled and gave them a bit of a patina, she says.

A number of artificial golds have been used over time.

Silver, which tarnishes and goes black unless it is covered with a yellow glaze, tinfoil, brass, and bronze paints and powders have all been used to simulate gilding, but they oxidise and become an ugly colour.

Restorers often have to take off old, ugly bronze paint on frames to bring an item back to its original appearance, she says.

Learn more

Jenny Sherman, paintings conservator, will demonstrate the art of gilding at 3pm on Sunday, March 20, at the Dunedin Public Art Gallery.

At 1.30pm on Sunday a tour of Beloved: Works from the Dunedin Public Art Gallery will focus on works that involve gold leaf or gold paint.