ALL YOU NEED TO KNOW ABOUT THE PROFESSION OF GILDER, GILDING THROUGH HISTORY, HOW TO RECOGNIZE GOLD LEAF, HOW TO TAKE CARE AND PRESERVE GILDED OBJECTS, HOW GOLD LEAF IS PRODUCED AND WHICH ARE THE MAIN GILDING TECHNIQUES TODAY.
By Steffy Chapul, Abian Curbelo, with the very precious collaboration of Donatienne Lurquin.
Gilding, a very old but also very contemporary technique.
The beginning of Gilding practices traces its roots back to 2300 BC in Egypt when royal goldsmith used to beat gold with a round stone to make thin plates or “gold foils”. In the High Antiquity Pharaohs tombstones as well as precious furniture and holy objects were used to be meticulously covered with those precious foils, since gold is a stainless and protective metal and was considered as a symbol of immortality and divinity.
A short time afterwards Phoenicians and Byzantines began to enhance the beauty of their sculptures and icons by gilding them or by illuminating their mosaics by the means of gilded tesserae. All along the following centuries, (Grece, Rome, Middle-Age) gilding has spread all over the world becoming a common practice through its different techniques.
Mercury gilding . While the gold beating practice was constantly improved to get thinner gold leaves, from the 3rd century BC in China, Italy and Greece appeared a second technique of gilding called the mercury gilding or fire gilding specifically made on metal structure or on glass (mirrors). This new technique implied that gold chloride was mixed with liquid mercury to obtain an amalgam. The new mixture would be later applied on a 400 °C heated-metal surface to remove mercury by evaporation and fix the gold (or silver). Since its re-introduction in Europe during the Renaissance, mercury gilding was commonly used to gild silver and bronze as well as for mirrors. However, being extremely poisoning for craftsmen, mercury gilding almost disappeared during the XIX century and ha been later forbidden. Technological progress replaced it with electroplating or electrolysis gilding.
Gold beating : the making of gold leaves
Gold is the most malleable and stretchable metal. One gram of gold could be stretched out over 3 kilometres. Nevertheless, in order to improve the working properties during the beating and obtain very thin leaves, a small quantity of silver and copper are often mixed with gold in order to obtain an alloy with 96% gold (or 23,75 carats) or a little less (23, 22, 21… carats) to obtain different shades of gold.
At the very beginning, the “gold foil” was thicker, sometimes even fixed with nails. Over the centuries, thanks to the improvement of gold purification and beating techniques, they have become increasingly fine until they became almost transparent “gold leaves”. Today, a gold leaf is 0.2 to 0.4 microns thick.
The technique of making gold leaves has not really changed since its creation. The different metals are put in a sand crucible and melted in a furnace at about 2000 degrees. The molten gold is then poured into an iron mould and makes a bar about 1,30 cm thick and 2,50 cm wide, and 30 cm long once cold.
The gold bar will be transformed into a ribbon thanks to several passes through a rolling mill which has the property of making the gold bar longer and thinner without changing its 2,50 cm width.
The ribbon will be cut into several 2,50 cm squares that will be placed between vellums (separating sheets made from calfskin). A 2,50 cm square will be pounded with a slightly convex head hammer until being a square of about 14 cm. The new square obtained will be cut into 4 equal squares and where each will be beaten until reaching around 13 cm. The same process will be repeated until the beater gets a new square of around 15 cm across. At this point from the 2,50 cm square could be made around sixteen leaves from 0.001 to 0.002 mm of thickness that would be sold after having their edges properly cut.
Nowadays, 1000 leaves of standard gold weight together between 12 and 20 grams.
To vary the colours and decorative effects, gold leaf can measure between 24 and 18 carats, and even between 14 and 6 carats (white gold). The most used gold leaf gilding and restoration is the 23 carats.
The gold leaves are sold in booklets of twenty-five units. The most common size in Europe is 8cm x 8cm. There are special tools intended to handle golden leaves because due to their extreme thinness, it is not possible to use hands.
While historically gold leaf was locally produced in European countries, nowadays an increasing offer from Asia is threatening European production with lower costs and often lower quality (gold leaf used as offerings for buddhas and temples). Some goldbeaters are still surviving in Italy and Germany but face hard times and look for new business models to compete with low cost offer while maintaining European standards of quality.
The Art of Gold Beating (1959) a video from British Pathé:
The use of Gold Leaf today
Gilders usually work closely with other professionals such as woodcarvers, cabinet makers, frame-makers, painting or frame restorers, upholsterers, bronze-workers, coppersmith, glass makers but also with architects and designers who need to enhance their creations. Gilders are used to working on varied types of support such as metals, wood, leather, glass, plaster, stone, paper, ceramics or even paintings.
Contemporary artists do not use gilding as often as they used to in the past. However, in contemporary design, some craftsmen are still using golden leaves while creating unique pieces for very exclusive clients, as Flavia Tummolo wonderfully does on her mural panels.
On the other hand, most of the gold leaves go to the restauration of antique furniture, frames and objects but also to indoor and outdoor architectural decorations. Professional gilder-restorers working for private (individuals, collectors, antique dealers, decorators) or public (museums, churches, historic monuments) clients, must have specific knowledge and training. Indeed, one cannot improvise as a gilder, even less a restorer, because the restoration of such pieces requires a thorough and scientific approach to gilding as well as a solid knowledge of Art History.
There are two main techniques for professional gold leaf gilding. Each has technical and historical variations, but this goes beyond the scope of this article. The differences between them lies basically in the process and materials used to prepare the surface before the application of the leaf.
So named because of its aqueous base, gilding with water is only possible for objects made of porous materials and for interior use. Mainly used for gilding on wood, water gilding requires solid technical knowledge and a lot of experience. It is based on the application of gold leaves on the wood, a layer of red clay (bole).
It consists in applying the gold leaves on the wood after numerous preliminary layers and operations which require warming and drying times between each.
- As a first step the gilder must prepare a perfectly smooth and regular surface, (called “levkas” for icons) by applying between 6 and 12 coats of a primer, made of chalk and rabbit skin glue.
- These primers must be re-sculpted using a specific tool to recreate the background and the details of decoration pasted by the several coats and then perfectly sanded to eliminate any imperfection.
- Bole. After the final coat, the primers are covered with several layers of “Bole”, that is to say a mixture of rabbit skin glue and clay (aka “Armenian Bole”, which contains iron oxide and is usually red but can also be yellow or brown or black). The surface of the bole will then be rubbed with a very hard brush, in order to obtain a very smooth effect. The preparation of the bole is crucial for the application of gold leaves and for the final burnishing in order to obtain a shiny and smooth effect, looking like solid gold, which will be enhanced by the red reflections brought by the transparency of the gold.
- Gold leaf application. This phase is of course the most delicate one since any dust grain, water drop, wind or external element could compromise it. Because of their thinness, gold leaves can only be touched with the gilder’s tools. Leaves are slipped from the booklet to the cushion by using the gilder’s knife and cut into smaller squares. They are then delicately placed on the previously moistened bole with a humid mop. Any air bubbles or holes will be removed with specific brushes. .
- Burnishing. The surface is polished with the agate stone, following circular movements until obtention of some mirror-brillant areas, contrasting with more mat ones. Excess of gold must be removed delicately. Where the sheet is torn or has not adhered, the gaps must be patched up.
- Once the surface is gilded and locally polished, some finishing are possible: matting of the hollows with skin glue, wear, patina, aging, protection with shellac or fish glue, etc.
Oil- size gilding
Although it can be used on porous objects prepared as above, oil-sized gilding is the only possible on non-porous objects in metal, glass, etc. and for all outdoor uses
Oil-size is a very viscous mordant obtained by cooking linseed oil at 150 ° C, added with resins and drying salts. When the mixture finely applied to the support is almost dry, after a drying time between 3 and 24 hours, it is ready to receive the gold leaf. (Photo : Aurore Davezac Lahoud – Gold Leaf on Glass)
This technique seems faster and simpler than water gilding, but the surfaces cannot be burnished, and the effect will be duller, mat and without nuances. If not applied by experienced professionals, the end result may look more like a painted surface than leaf gilded.
Moreover, for qualitative and long lasting results, close to water gilding, surfaces must be very carefully prepared, according to their nature, cases and use: sealers, insulation, pickling, sanding, anti-corrosion protection, glossy paints, colouring, etc.
Since the advent of synthetic products, there have also been mixtures based on water and vinyl or acrylic resins. However, these are not very reversible, neither solid and can be only used for indoor and decorative applications. These products are to be avoided in restoration of antiques and art pieces
All what shines (or looks like gold) is not gold!
If water gilding was the most used technique until the end of the 18th century, that changed thereafter: according to the times, the trends, the type of object, its destination, the budget … and especially according to the subsequent interventions by owners or restorers. We can find many other materials and techniques on gilded wood, sometimes used concomitantly: silver leaves covered with yellow varnish, brass leaves …, placed either with water based mixture or oil size. But we can also find hot foiled gilding, golden paints, “bronzines” (varnish or wax mixed with brass powder) and more recently mica powders.
These choices, originally made or due to subsequent interventions, have of course consequences on the aesthetic quality of the object (especially over time, because the ersatz gilding age very badly), but also on its heritage or market value, and on its maintenance , its conservation and restoration.
Other gilding techniques
Gilding by firing / fusion, used for ceramics and glass: gold leaf or gold salts are applied to the object, the whole is then put in the oven on low heat to fix by fusion. See the work of Léa Schroder and Danielle Adjoubel. (Photo : vase gilded wth 2 coats of mat gold 24% – Danielle Adjoubel )
The technique of “Zwischen Goldglas” commonly used on glass and adopted between the 17th and the 19th century in Bohemia, consists in sticking a decoration with gold leaf between two glass surfaces. After possible etching of the gold, the two layers of glass are hot moulded together. (Jug with lid of Zwischengold glass, with a powder keg with weapon trophy and a flower basket, anonymous, Bohemia, 1720 – 1740)
DANIEL Lopez-Obrero – Gilder on leather with the “Cordovan Technique” .
Daniel Lopez-Obrero represents the third generation of a family business whose main objective is to preserve the so-called Cordovan technique (Cordoba leather and embossed leather) which was initiated in the 10th century during the Hispano-Muslim era and has continued during the Renaissance and the Baroque. Cordovan art continued until the 18th century and gradually disappeared. Today, only a few artisans continue to apply it. Also known as guadamacile (from Ghadames, the Libyan city where it was first used), this technique mixes gilding with gold or silver leaf on very fine leather surfaces, with further embossing of the leather and a final painted finish.
Gilding on leather also refers to the work of BOOK BINDERS and SHEATH MAKERS : these, are specialized in the leather covering of books, desks and furniture, cases, sheaths, etc. Their work often ends with the application of patterns, ornaments, threads or texts in gold. But here, the gold leaf is embedded in the leather by pressing irons and bronze casters heated with fire.
EDGE GILDING – Finally, some book binders and some gilders master the technique of EDGE GILDING. The Book edges are gilded according to a variant of water gilding, in very thin thickness and by using a press.
Watch out for the gilding
The restoration and conservation of gilding requires large studies prior to restoration or conservation in order to understand the causes of damage, which may be due to environmental, biological, physical or even human factors.
The most common cause of the degradation is humidity, which by altering the rabbit skin glue, affects both the layers of preparation and the red clay. These strata can lose their adhesion and decompose and deteriorate the gilded surface.
Two types of action can be carried out on any material object: conservation interventions and restoration interventions. It is always preferable to undertake a preventive conservation that delays or prevents a direct intervention on the object.
In any case, the restoration of gilding requires interdisciplinary work and great knowledge about techniques. Restoration must be the least aggressive possible. In addition to the above-mentioned factors, the quality of the gold must correspond to the one which was originally used. Restauration’s masterpieces based on ”bronzine” (bronze and other metals powder), are one of the best examples of a nearly irreversible mistakes. These metals age rapidly and will turn green due to the oxidation of copper.
How to take care of and preserve your gilded wood (frames, mirrors, seats, console, statue, icon, pendulum, panels, stucco, etc.) Gold is eternal, unalterable, stainless, but when it is laid down in leaves …:
- Its extreme thickness (0.2µ) makes it particularly fragile.
- His laying techniques, with water or oil, require specific precautions.
- Its longevity will also depend on the behaviour of the underlying layers (chalk finishes, stucco decorations, bole, etc.) and therefore of course on the support itself (sanitary condition of the wood, solidity of the frame, etc. .).
- Therefore, the atmospheric conditions (humidity and T °), hanging and handling are essential in the long term.
- Unless sealed enclosure, you will not avoid dust or fatty deposits (microbial impact).
Here is what to do, and especially NOT to do, to ensure the beauty and longevity of your golden leaf objects:…
Questions à : Danielle Adjoubel – Dorure sur porcelaine
- I rather use matt gold in liquid form, of viscous and black type, pure at 24% and 32%. Sometimes I take the brilliant gold at 12%, it depends on the result that I want to obtain. I always put it on an enamel surface, with very clean specific brushes.
- There is no possible retouching, any traces left after cooking can sometimes be removed with corrosive products but with the risk of veiling the enamel or even having to throw the whole piece!
- Whatever the percentage of gold used, it is necessary to mix for a long time and carefully with a small glass stick, at room temperature and proceed to the application in the following order: 1 layer of shiny or mat gold + cooking + 1 layer matt gold + firing and polishing
- Depending on the price of the piece and / or the delicacy of the work, I vary the gold percentages. The application of gold leaf is also possible; however, it tends to “fly away” during firing with a different and uncontrollable effect.
A NEW BUSINESS MODEL TO KEEP ITALIAN KNOW HOW ALIVE Interview with Elena ORIANI, CEO of Brambilla Battiloro
” Our vision is that of a world without borders and we must therefore open up the opportunities it offers us. When the Chinese product arrived on the European market and beyond, 20 years ago, our choice was to open a company in an emerging country (Senegal) to join our Italian production. It was not easy, of course, but today we can still sell a product that derives from a strictly European manufacturing and know how.
What is very important to say isthat all the raw materials that we use are bought in Europe. And in the case of gold and silver, platinum and palladium, this gives us the guarantee of having a purity of 100% of the metal thanks to the refining methods required by European standards.
We are in 2020 and the help that the web offers us is undeniable … but nothing equals the sound of a voice and the possibility of asking a question about a gilding problem or the choice of a product to somebody who will help you find a solution. We are always at the service of the customer!
In general, the products are recommended after a prior interview with the customer. We are dealing with a product that embellishes artistic heritage and we must be very careful about the way we act. From us, whenever the customer requests it, a certificate of the product sold is issued as proof of the authenticity of the sheets. The real master is the artist, we are the element that can make the difference.”