Gilding is the art of applying gold or other metals to a surface. My interest in gilding is in the art of calligraphy, where gilding has traditionally been an important decorative method.

Some of the most impressive examples of gilding are found in ancient manuscripts such as the Book of Kells. It is a very old art, and has changed very little since the 8th or 9th centuries when such manuscripts were frequently created.

Gilding has traditionally used gesso to fix the gold to the surface (usually either vellum or paper). A mixture of PVA glue and water (known as size or gilding medium) can be used, but does not give the impressive results or the durability of gesso.

When gilding, the fixative is applied to the area of the design to be gilded. Gesso is applied as a puddle, and while size is usually painted thinly on to the paper, an attractive result can be obtained by “puddling” the size onto the paper in a similar manner to gesso application. The fixative is allowed to dry for between 40 minutes (for thinly applied size) to 7 days (for some types of gesso). Once dry, the fixative must be breathed on to give a slightly tacky surface. Gold leaf is applied and firmly burnished or polished. Haematite or quartz is often used as a burnisher, with other polishing substances including glassine paper and silk. Gold applied with size cannot be as firmly burnished as gold applied with gesso, and does not obtain the beautiful sheen given with gesso. However, using size is an almost failsafe method, while gesso is very temperamental.

The adherence of the gold to the gesso is affected by temperature, humidity, the strength of the burnishing, and the number of times the artist breathes on the gesso prior to gilding. It is a very difficult art to master, but the results are stunningly beautiful.

Gold is the most frequently used metal for gilding, as it does not tarnish. Silver leaf gives a beautiful effect, but some tarnishing must be expected. This tarnishing often gives an attractive effect of its own, and in fact many calligraphers and illuminators deliberately do not seal their silver leaf gilding against tarnishing, in order to achieve this effect. Copper leaf is occasionally used, including a product called variegated copper – which has been treated to give many colours in the same sheet of foil. The Australian calligrapher Dave Wood is currently using beautiful deep blue and green gilding foils – however as yet I have been unable to discover a source for this. He guards his secrets well.

Most gilding products can be obtained at any specialty art or calligraphy shop. They are less expensive than one would assume – a 10 by 10 cm square of gold leaf is around A$2.50

Additional: SEF pointed out that the Byzantine icons from the early days of the church also featured a large amount of gilding, which was applied using various different techniques, the gesso method was only occasionally used.

Water gilding was probably the most common – a technique where gilder’s clay or “bole” is applied to the surface, usually wood, with gilder’s size. Methods seem to vary – the bole (a red, grey or black paste) can either be mixed with an animal glue, or (I believe) at times comes ready mixed. In some methods the bole is also applied with gilder’s liquor – a mix of water and alcohol. The gold leaf is then laid onto the dampened bole, and will be cemented to the surface. The leaf, once the bole is dry, can be burnished as if for gesso gilding.

Oil or “mordant” gilding is similar to gilding with size or gilder’s medium. Simply, an oil based size is used as the fixative, left a while for the proper tackiness to develop, then gold leaf is applied. Like gilding with normal size, this method will not stand up to much burnishing, and will not develop the mirror-like sheen of gesso or water gilding.

An additional method of applying gold to a surface, which I did not refer to in my original write up, and should have, is using shell gold. This is gold in a powder form, mixed with a fixative. It is applied with a brush, and can be burnished only lightly. It will never attain the sheen of gold leaf, but is useful for very small, detailed work, or to apply gold on top of paints (gold leaf can sometimes adhere to the paint). I believe this method was used on the Byzantine icons, but cannot be sure. It is certainly used by modern icon painters.

Acknowledgements:, and SEF, cause I didn’t have the foggiest about the Byzantine icons before.