The Crucifixion (about 1369-70) by Jacopo di CioneThe National Gallery, London
'The Crucifixion' is a small altarpiece, painted in Florence around 1369-70 by Jacopo di Cione, with the possible assistance of another painter. It shows Christ and two thieves on the cross, surrounded by depictions of saints and three-dimensional architectural flourishes.
Perhaps the most striking aspect of this picture is its large-scale use of gold.
The Virgin and Child with Saints Dominic and Aurea (about 1312-15 (?)) by DuccioThe National Gallery, London
Gold is a prominent feature of 14th-century Florentine paintings. It is often one of the first things you notice about them. For example in this picture by Duccio (also in the National Gallery Collection).
But why were painters so interested in using gold, and on such a large scale?
The Crucifixion (about 1369-70) by Jacopo di CioneThe National Gallery, London
Why gold?
Gold was often used because it symbolised the divine. It was relatively easy to work with, did not tarnish over time and could be used to create gleaming, shimmering effects through the use of different gilding techniques (ways of applying gold).
Close up of gold leaf being applied to a surfaceThe National Gallery, London
Gold is relatively easy to work with because it is so soft, or malleable. The gold used in painting is made by hammering gold coins flat to make extremely thin sheets called ‘gold leaf’. These leaves are so thin that they are moved around using a brush - like the one seen here.
Head of the National Gallery Scientific department, Marika Spring, using the scanning electron microscope to analyse paint samples. (2010)The National Gallery, London
Gilding techniques - applying gold
Scientists at the National Gallery have amassed an understanding of gilding techniques largely through two sources: a well-established treatise on painting techniques written by Cennino Cennini in the 14th century, and from their own research into these techniques and materials.
The Crucifixion (about 1369-70) by Jacopo di CioneThe National Gallery, London
'The Crucifixion' is exceptional for its many different ways of using gold. On this picture we can see examples of these gilding techniques, including water gilding, pastiglia, punch marks, mordant gilding and shell gold...
Gold leaf and some tools for water gildingThe National Gallery, London
Water gilding
Water gilding is used to make large, glossy expanses of gold. First a surface must be made flat through painstaking layering of glue size (liquid animal glue) and gesso (a form of calcium sulphate), followed by a thick layer of red bole (a slippery clay rich in iron oxide).
A thin layer of water is brushed onto to this layer and then the gold leaf gently placed on top. The gold surface is then burnished until smooth. Gold leaf is so thin that when it is applied on top of the bole the red colour shines through, giving the gold a warm glow.
The Crucifixion (about 1369-70) by Jacopo di CioneThe National Gallery, London
The final product looks like a solid block of gold. However, if we look closely at the small scratches in the gilded background of 'The Crucifixion' we can just see hints of the red bole layered beneath.
Adding texture
The flat expanse of water gilding can also be textured using tools to create incised lines, rings and punch marks. This breaks up the uniformity of the gold and makes it shimmer, creating beautiful ornamental effects. The haloes in 'The Crucifixion' were created in this way.
Pastiglia
Three dimensional gilded patterns can be made using pastiglia (applying thick gesso to make a raised design before applying the bole, water and gold). Pastiglia can be seen in the floral decoration throughout the outer frame and architectural elements.
Mordant gilding
Mordant gilding is used to create gold details. A sticky adhesive, or ‘mordant’ (usually made of pigmented oil), is added onto the painted surface. The gold leaf is applied and sticks to the mordant. In 'The Crucifixion', this method is used to create embellishments on fabric.
Shell Gold
Gold leaf can be ground into powder and mixed with a binder (i.e. egg tempera or oil) just like paint. This makes 'shell gold' which is used to create very fine details. The intricate decoration on Christ’s loincloth is likely to have been painted in shell gold.
Shell Silver
It is not just gold that can be treated in this way. Other metals, such as silver, can also be beaten into sheets and ground up in a binder to create a paint. Many details in 'The Crucifixion' were made with shell silver, such as the armour and the tips of the raised lances.
These fine silver details would have originally shone bright, contrasting with the warm glow created by the large expanse of gold. Unfortunately, silver is much more reactive than gold and tarnishes over time, as such, the areas in which shell silver was used now look dark brown.
Fortunately, the delicate gilding techniques and long-lasting properties of gold have kept this picture looking golden, and we can continue to admire the incredible craftsmanship and shining beauty of 'The Crucifixion' today.
