Throughout history, mankind has lusted after the incomparably rich color of gold. But gold's high value has traditionally limited gold jewelry, tableware and decorations to the very wealthiest members of society. During ancient times though, ingenious alchemists developed a way around this problem - gold plating. Gold plating, also called gilding, is a process where gold is either mechanically or chemically adhered to another substance, usually a less expensive metal.
One very special kind of gilding process, however, was far superior to all the others. It was called mercury gilding and it produced the most beautiful gilt objects known to man. Mercury gilding, as the name implies, involved mixing pure gold together with liquid mercury to form a paste-like amalgam. This gold-mercury amalgam was then brushed onto the surface of a silver, copper, brass or bronze object.
Once the item had been covered with the amalgam, it was heated in a furnace until the mercury vaporized. Because mercury's boiling point is so low (674°F or 357°C), the mercury is driven off by the heat, leaving the gold from the amalgam strongly bonded to the surface of the object. As a final step, the freshly gilt item was burnished or polished using an agate tool. This gave a bright, high purity gold finish that was both beautiful and durable.
Mercury gilding, also known as fire gilding, has been known since ancient times. The ancient Greek, Roman, Persian and Chinese civilizations all used mercury gilding extensively for jewelry, statues and other objet d'art. But there was an alternative ancient gilding method that used gold leaf. In this process sheets of gold leaf were carefully adhered to a clean metal surface and then burnished, permanently bonding the gold leaf to the underlying metal. However, gold leaf gilding was very thin compared to mercury gilding and also inferior in other ways.
For example, mercury gilding gave a very even, uniform coating of gold over an entire object. In addition, the heating process in fire gilding actually diffused gold into the surface of the underlying metal, making the gold layer particularly tough and long wearing. Finally, mercury gilding left a much thicker layer of gold versus gold leaf. If desired, the fire gilding process could be repeated several times, increasing the gold thickness even more.
Due to these advantages, mercury gilding was the preferred method of gilding for over 2000 years. The process of fire gilding was steadily refined over the centuries until it had evolved into a high art form in Europe by the Italian Renaissance. Later, the French aristocracy's love of opulent gold decoration, along with the rise of the lavish, baroque-inspired Louis XIV style, naturally propelled France into a commanding position in the art of fire gilding.
In fact, the French loved gilding so much that they bequeathed two different terms for it to the English language: vermeil and ormolu. Vermeil refers to gold-plating over a solid silver alloy base while ormolu is fire gilding over a copper alloy object. The term vermeil is still in popular usage today, usually in reference to jewelry.
As dazzling as mercury gilding was, it had one major drawback. Mercury is a toxic heavy metal that causes terrible neurological symptoms after prolonged exposure, followed by death. In fact, the Victorian saying "mad as a hatter" specifically referred to mercury poisoning. This is because hat makers were routinely exposed to mercury nitrate in the hat making process until the late 19th century.
Gilders suffered a similar occupational hazard, with few surviving much beyond the age of 40. Although poisoning from liquid mercury at room temperature was unlikely, the fire gilding process required that the gold-infused amalgam be heated until the mercury evaporated. The resulting mercury vapor was easily inhaled, leading to chronic and debilitating health problems for gilders.
Eventually a more technologically advanced type of gold plating, called electroplating, was discovered. The concept of electroplating was first published by an Italian scientist, Luigi Brugnatelli, in 1805. However, it was not commercially viable until an improved process was developed in Britain by George and Henry Elkington in 1840.
This new electroplating method of gilding was much cheaper, easier and safer than the old mercury gilding process, even if the results were somewhat inferior. As a result, gold electroplating rapidly displaced the superior fire gilding process starting in the 1840s. By the end of France's 2nd Empire in 1870, the traditional method of mercury gilding was effectively obsolete.
Amazingly enough, it is still possible for antique collectors and investors to purchase exquisite mercury gilt antiques from the 18th and early 19th century for relatively modest sums. Even antiques made in the mid 19th century, between 1840 and 1870, have a fair chance of being fire gilt, especially if French in origin. The fact that these glittering works of art have so effortlessly survived the centuries is a testament to the considerable craftsmanship and fortitude that went into their production.
