Figure of the month: 100 nanometers

Gilded picture frames, gold-plated stucco, gilt edges on books and golden figurines have one thing in common: in most cases, it really is gold that glitters. In order to keep the production costs of gilded objects as low as possible, however, extremely thinly beaten gold is used, consisting mainly of pure gold but only 100 nanometres thick. Thus, 10,000 sheets of gold leaf stacked on top of each other would result in a stack just one millimetre high. 

The production of beaten gold is demanding: first, gold is melted down and silver or copper can be added if the gold colour is to be lightened or darkened. This alloy is then cast into a ingot mould for cooling and rolled out by a gold beater to a thickness of 0.07 millimetres. Small squares are cut out of them, separated from each other with the help of Montgolfier paper, and then stacked 600 times on top of each other. The thickness of the gold leaves is further reduced in a squeezing machine. Again, squares are cut from these leaves and the process is repeated, among other things, by hammer beating until the desired thickness of 100 nanometres is reached.

Two is better than one – even when it comes to beaten gold

As is well known, gold is not only extremely ductile and flexible, but also very resilient. It is not subject to corrosion caused by environmental influences. Despite its low thickness, even beaten gold is very durable – how durable depends on the type of beaten gold used. The most commonly used types of gold leaf are 100 nanometres thick single gold, as well as double gold, the latter with a thickness of 200 nanometres. According to the German gold beating company Eytzinger, a gold plating of an outdoors object with single gold usually lasts some 25 years, increased to around 35 years if double gold was used.