Gilding is the art of applying gold leaf to a surface. Techniques were developed by the ancients to gild wood, metals and other materials. Because of the comparative thickness of the gold leaf used in ancient gilding, the traces that remain are remarkably brilliant and solid.

          Gilding has all through history occupied an important place in the ornamental arts of countries around the world; and the native processes pursued at the present day may be taken as typical of the arts as practised from the earliest periods.

                Metals that are made into metal leaf need to be highly malleable. They can be pounded into sheets well below a micrometre in thickness without breaking or tearing. The typical thickness of gold leaf is about 100 nanometres or 0.0001 mm. When made by hand, small pieces of annealed metal are placed between sheets of parchment and pounded repeatedly with wooden mallets. As the metal thins out, it forms large sheets. These sheets are divided and the process repeated. The final sheets of metal are trimmed, cut to various sizes, and sandwiched between sheets of paper to protect them.

At a thickness of 100 nm one square metre of gold leaf corresponds to 0.1 cubic centimetre or less than 2 grams of gold. One ounce of gold would cover at least 14 square metres.         

    

                 Oil gilding is a very traditional process. After the surface is prepared by cleaning, sanding, sealing, priming, and coating with an impervious lacquer or enamel, a "size" of linseed and other oils similar to varnish, is applied. The size cures until it comes to tack (that is, it has dried enough to hold the leaf on to the surface but is still "tacky" enough for the leaf to adhere to it). This can vary between a 3, 12 or 24 hour size. The larger the area being gilded, the longer “open time” needed to complete the transfer of gold.

The leaf is cut to the appropriate size with a gilder’s knife on a pad of calf’s leather and transferred with a tip (a very soft squirrel hair brush) and static electricity (which picks up the gold). The surface is then skewed with soft brushes (a gilder’s mop of squirrel hair), cotton wool or sable hair to fully press the leaf against the size and also remove any loose fragments of leaf. Oil gilded surfaces are not burnished any further but a final polishing removes all traces of gold dust fully revealing the beauty and lustre.

Any draughts or movement of air including heavy breathing and the gold leaf is likely to fly off the pad! Outdoor projects such as the domes of buildings and large statues need a temporary structure around them to eliminate any wind as well as control the temperature and humidity.

         

                 The gold leaf used in my studio is Fine Antique Yellow 23 3/4 Karat. Leaf is available from specialist art suppliers in booklets of 25 leaves, 80 or 85 mm square, and either loose or attached to a backing paper for easy transfer.

Gold-leaf comes in a variety of different colours and karats: e.g. an 18 Karat green gold-leaf would have a 25% alloy of silver, zinc and copper mixed in to the gold. Blue gold would have iron etc. Genuine Silver leaf is also manufactured as well as “Dutch Gold”, an imitation gold, usually 80% copper and 20% zinc.