Recently I have been doing research on some pieces of Slavic jewelry. I was discussing the type of surface decoration on this jewelry with a customer, and when I mentioned niello, I got a blank stare. So, I knew it was time for another metal techniques blog.
Niello is a type of surface decoration that uses the differences in the natural color of two metals to create a contrasting design. Niello is most commonly used on gold, silver, bronze, and steel. The Sutton Hoo Buckle that is shown above uses niello to emphasize the knot work designs.
The process of decorating an object with niello can be summarized as follows. The jewelry is created. It does not matter whether it is cast, soldered together or riveted, but the piece should be ready for final decoration. The surface is then engraved, etched, or chased to create depressions in the metal to hold the niello compound. It is also possible to create these depressions in the metal’s surface during the casting process. The depressions should be shallow, usually between 1/32″ and 1/64″. Deeper depressions may result in pitting or bubbling of the niello.
Modernly, most Western jewelers purchase pre-made niello from a supply house, but it can be made in the shop. There are many different recipes available, but most of them use silver, copper, lead and sulphur. The carefully cleaned metals are weighed, according to the recipe that you are using, and then melted in a crucible, using either a torch or kiln. The melting process starts with the metal with the highest melting point, silver, then progressing to copper, and finally lead. Once all of the metals are melted the mixture is stirred with a charcoal stick to mix them thoroughly. Next the sulphur needs to be added. Some people preheat the sulphur in another crucible and add the molten metal to it, while others simply add the sulphur to the crucible containing the molten metal. The molten solution is then stirred with a graphite rod to ensure a proper mix.
The molten niello is then poured out onto a slightly oiled steel slab, and while still hot it is hammered out to make it fairly thin. A torch can be used to keep it hot if more hammering is required. The niello is allowed to cool. It is first broken up with a hammer and then ground with a mortar and pestle until all of the particles can pass through an 80-mesh sieve. For very fine lines, niello can be ground finer.
To use niello, it is first washed, like enamel, to remove any foreign particles. It suffers from the same problem as enamel: oxidation over time. The use of an airtight container to store niello that has been completely dried, will help extend its lifespan. Storing niello in lump form is another option.
The surface to which the niello is to be applied must be clean. The surface is painted with a borax solution and wet niello powder is placed in the depressions. The niello will shrink when heated, so it must be mounded slightly. Use the least amount possible, because excess niello will need to be removed by filing after it is fused. Allow the niello and borax to dry completely, place the piece in a 1000°F kiln, and watch for the surface of the niello to become smooth. As soon as the surface is smooth remove the piece from the kiln and allow it to air cool. When the piece is cooled completely the surface should be filed, ground, and polished to remove all excess niello.
I hope that this brief blog gives you a better idea of the origins of many of those wonderful designs that we find in ancient jewelry and armor pieces, and even a few modern pieces.