We touched on the topic of shell gold during our fascinating workshop in Cambridge with Dr Spike Bucklow at the Hamilton Karr Institute last October (see the blog entry here). I was immediately intrigued by the technique and wondered about producing shell gold myself. For this blog post, I asked myself what exactly the historical technique of shell gold is, when and where it was used and – more importantly – how difficult it is to produce.
Shell gold is a technique for which powdered gold leaf and a binder material are mixed together in a sea shell – hence the name. There are a number of different recipes for shell gold, which mention different binder materials, including gum arabic, egg-white (the adhesive known as “glair”), and warm fish glue. In his work De diversis artibus, written in the early twelfth century, Theophilus Presbyter (fl. ca. 1070–1125) recommends boiling the bladders of sturgeons until the whole mixture becomes sticky. He also advises grinding the gold for several hours in a mortar. In contrast, the artist Cennino Cennini (ca. 1330–ca. 1440) in his Libro dell’Arte written around 1400 recommends placing gold leaf on a stone and grinding it into tiny flakes with a pestle. As the binder material he advises using either glair or gum arabic. Several treatises also mention using sea salt to grind the gold leaf; a technique I chose for my own experiment (see below). After the shell gold has been applied to parchment, paper, or canvas it can be brightened – like gold leaf – with a burnisher. In contrast to the brightening of gold leaf, with shell gold one has to be careful to not wipe it off. The different effects produced mean that it is often possible to clearly distinguish with the naked eye between gold-leaf gilding and shell gold (Morgan 2016, 193–195; Whitley 2000, 181–183).
In the Middle Ages and the early modern period shell gold was mainly used for illuminating manuscripts, especially for the ornamentation of scripts and for illustrations (Morgan 2016, 193). An important depiction of the use of shell gold can be found in the Allegory for Abraham Ortelius by the famous illuminator and miniaturist Joris Hoefnagel (Fig. 1). The left side of this drawing is dedicated to Abraham Ortelius and depicts his compasses and writing instruments while the right side shows three shells in which different colours have been ground and made into paint along with various brushes and pens – tools used by Hoefnagel for his work. Interestingly, one of the shells is filled with gold – shell gold – and it seems that details of the drawing have been executed with this material (i.e. the snakes of the caduceus and the inscriptions). In rare cases, shell gold was also used in panel painting as for example in Sandro Botticelli’s famous The Birth of Venus produced around 1486. In it, parts of Venus’s hair were executed in shell gold by the Florentine painter (Straub 1984, 240).
Shells with gold encrusted inside them were also seen as objects worth collecting. The account book of Archduke Ernest of Austria (1553–1595) contains the following entry: “Per 145 muscheln mit goldt, 10 fl. 27 kr.” (Haupt/Wied 2010, 234). As the archduke most likely bought these shells in Antwerp – a flourishing centre of artisanal practice at this time – one can assume that the entry refers to shells formerly used to produce shell gold which were still adorned with the remains of the gold leaf on the inside. Interestingly, there are shell-gold shells on display in the exhibition Kunst- und Wunderkammer at Castle Trausnitz, a branch of the Bayerisches Nationalmuseum, where objects from the collection of the House of Wittelsbach are displayed.
As mentioned above, since October I have been intrigued by the idea of producing shell gold myself. Following Cennini’s advice to “be careful to collect the small pieces of gold” (Cennini 1899, 111), I collected up all the residue left over after our hands-on session in Cambridge when we had attached gold leaf to paper using linseed oil. Spike Bucklow kindly provided me with a recipe (Fig. 2) as well as with the gum arabic required to produce the shell gold. (Gum arabic is the hardened sap of various species of the acacia tree.)
First of all, I gathered all the necessary ingredients: the remaining parts of the gold leaf, mussel shells, gum arabic, sea salt, a brush and water, as well as a little bowl (Fig. 3).
In the next step, I mixed the pieces of gold leaf with sea salt in the mussel shell (Fig. 6). As you can see in Fig. 7, the salt ground the gold leaf into tiny flakes. As already observed in the work with gold leaf in October, the gold-flakes were quite sticky and I had some problems removing them from my finger.
I then repeated these last steps once again – grinding the gold with sea salt, mixing it with water, waiting till the salt dissolved and finally decanting the water. In the following step, I added the gum arabic to the gold in the shell and mixed them together. The shell gold was now ready and could be applied to paper with a pen or a brush (Fig. 12).
Even though the recipe seems rather simple, it nevertheless took quite a long time. In the end, this little home-made experiment helped me to achieve a better understanding of the material gold and its handling through my own hands-on experience with this intriguing artisanal technique of making shell gold.
The Book of the Art of Cennino Cennini: A Contemporary Practical Treatise on Quattrocento Painting, trans. by Christiana J. Herringham. London: George Allan, Ruskin House, 1899.
Herbert Haupt and Alexander Wied, “Erzherzog Ernst von Österreich (1553–1595): Statthalter der Spanischen Niederlande; Das Kassabuch der Jahre 1589 bis 1595,” Jahrbuch des Kunsthistorischen Museums Wien 12 (2010): 153–275.
Nigel Morgan, “Painting with Gold and Silver.” In Colour: The Art and Science of Illuminated Manuscripts, ed. by Stella Panayotova with the assistance of Deirdre Jackson and Paola Ricciardi, 193–199. London/Turnhout: Harvey Miller Publisher, 2016. Exhibition Catalogue.
Rolf E. Straub, “Tafel- und Tüchleinmalerei des Mittelalters.” In Reclams Handbuch der künstlerischen Techniken, vol. 1, 131–259. Stuttgart: Reclam, 1984.
Kathleen P. Whitley, The Gilded Page: The History and Technique of Manuscript Gilding. London/New Castle: British Library and Oak Knoll Press, 2000.