The gilding process essentially entails applying a layer of gold onto the surface of another material. The art of gilding objects has been around since antiquity, mainly done with liturgical and ritual items. Gilding was, and still is, used to make the object look fancier and more luxurious.
The craft of gilding was closely related to the craft of goldbeating. These processes don’t just belong to the past, though, as both of these techniques are still alive today, especially among restorers.
Gold leaf gilding, which means applying gold leaf onto the surface of another material, is a widely known technique. However, when it comes to the art of jewellery production, other techniques of gilding are our main focus. These include methods like fire gilding, creating gold-filled items, gold plating and PVD gilding. Other methods are also used for gilding ceramics, glass and porcelain.
We will provide more information on these individual methods later in this article, but let’s first find out how to distinguish a gold jewel from a gilded one and why you should avoid gilded jewels.
How to recognize a gilded jewel
Jewellery is usually gilded for the aesthetic aspect. The majority of the time, it’s silver that is gilded in order to look like gold. Our experience in this industry has taught us that gilded jewels usually have a distinct, tacky yellow colour. Also, the gold layer on a gilded jewel wears down over time, and the real state of the jewellery will show through.
In the Czech Republic, we can tell whether a jewel is gilded by its hallmark. The hallmark always reveals the material the jewel is made of. For example, gold-plated silver will bear a hallmark of 925. 14-karat gold jewellery will carry a hallmark of 585 as well as a national hallmark, ensuring the gold’s authenticity.
Since any conductive metal can be gilded, we recommend buying jewellery only from verified sellers and, for Czech jewellery, always checking whether the jewel has a national hallmark. We say this because in the Czech Republic specifically, every gold jewel with a weight of more than 0.5 g has to have a national hallmark stating its purity, which is different than its 585 hallmark (in the case of 14-karat gold), which can be used by anyone. For 14-karat gold, the national hallmark is a goose in a hexagon with the number 4. In silver jewels, the national hallmark is required on jewellery weighing 3.5 g or more.
In countries other than the Czech Republic, we need to be more careful, as the control of precious metal sales might not be as strict. Unfortunately, tourists are seen as easy prey for fraudsters, and a gold ring you bring home from your holiday might turn out to be gilded copper.
Why gold should be the preferred choice
Nowadays in our workshop, we most often find gilded chains when they’re brought into us for repairs. In general, we recommend avoiding gilded jewellery. If you have a gilded chain and purchase a pendant made from real gold, the pendant will have a different, lighter colour than the chain, so the two won’t complement each other. Moreover, gilded jewels cannot be polished, so they might appear duller, and during repairs or restorations, a new layer of gold will be needed, which, of course, will not look as good as the first layer.
Therefore, gilded jewels are rather short-term investments. Investments in real gold are always long-term. Even in the case of irreparable damage, gold jewellery can always be monetized again, as many jewellery stores buy gold back. On the other hand, the return on gilded or gold-plated silver jewels is not significant. Gilded jewels from common metals don’t hold any great value, nor can they be repaired if they’re damaged.
Gold leaf gilding
Gold leaf gilding is the easiest method of covering the surface of a metal or non-metal object with gold. It is a mechanical method when gold foil, also known as gold leaf, is applied to an object. This foil is prepared by goldbeaters. In their profession, goldbeaters use molds, interleaving material (like parchment or ox intestine membranes, which have in large part been replaced these days) and hammers. Almost nothing has changed in goldbeating technology since the Middle Ages.
Gold is prepared into an alloy which is melted into an ingot (a product created for further processing), rolled into a ribbon to a thickness of 0.02 mm and cut into 4x4 cm squares. 380 to 450 of these squares are put into the first mold, the so-called cutch. Then, the gold is processed by an electric hammer (hammer mills were used in the past) into ribbons with a thickness of 0.005 mm and measuring 130×130 mm. This gold, called cutch or Zwishgold, was used to gild altars in the Middle Ages.
The ribbons are then cut into 4 identical parts and 1,500 pieces are put inside a second mold, the so-called lot. Then, the electric hammer is used again, and the ribbons are thinned to a thickness of 0.001 mm. Each ribbon is then divided into 4 parts again and 1,440 pieces of them are put into the last mold. This next step is the most difficult, as the goldbeater uses a fifteen-pound hammer to beat the ribbons until they are only 0.0001 mm thick. This requires 2.5 hours of precise, intense work with the hammer so that the gold is beaten evenly and isn’t torn. One m2 of such a thin ribbon weighs 2.45 g. At this time, the work of the goldbeaters is complete, and the gilders take over.
This process has also remained for the most part unchanged for centuries. In ancient times, all it took was burnishing the gold foil on a rough surface and the gilding was done. For books, the gold leaf was glued with egg whites. For wood (picture frames, for example), glues made from animals were used for adhesion. However, wooden surfaces had to be thoroughly prepared to be perfectly smooth. Only then could the gilder start applying the thin layers of gold, which had been previously cut into desired pieces on a leather pad with a knife. To apply the gold layers, a gilder’s tip is used. After application, a burnisher is needed for perfect burnishing. The gilded surface can be further decorated by extruding. In the end, the whole object is coated with shellac for protection.
Different gilding methods
Other methods of gilding include applying gold onto the object using a chemical reaction or other physical basis. These methods are used for gilding jewellery.
The oldest technique of gilding is fire gilding. Gold amalgam (a solution of gold in mercury) is used in this process, and the whole gilded object is covered in it. Then, it is heated in fire and the produced layer of gold is burnished. Depending on various additives, various colours of gold can be achieved. Such gilding is permanent and durable. It was used for gilding sacred objects, goblets, sacred vessels and similar things. Since this method is only possible by using mercury, which is very toxic, it is no longer implemented.
Another very old method of gilding is creating gold-filled items. A gold sheet is welded onto a thicker brass or tombac sheet. This combination is then rolled until it reaches the desired thickness. The gold sticks to the base very well. Metal sheets created this way used to be common in jewellery production. Nowadays, it is mostly used for watch cases.
Nowadays, the most common technique is gold plating. The object to be gold plated is immersed as a cathode into a gilding bath which contains a solution with gold cyanide. By introducing an electric current, a thin layer of pure gold adheres to the object. This method of gilding can create a layer of any desired thickness, usually several tens of microns. However, this method is not as durable as that of gold-filled items. Experienced jewelers can usually recognize gold-plated jewellery at first glance.
The most modern technique of gilding is called Physical Vapor Deposition, i.e. PVD gilding. This process takes place in a vacuum. Gold is vaporised in an airless tank using electricity. Then, it deposits on colder surfaces. This way, an extremely thin layer of gold is created that has the ability to cling to the tiniest of detailing. This is used for the preparation of specimens for electron microscopy.
Gilding glass, ceramics and porcelain
Glass, ceramics and porcelain are gilded by firing. The desired decoration is produced on the foundation using a gold paste, and then it is fired. This technique is permanent but also pretty costly. Therefore, these days it has for the most part been replaced by other materials.