That cloudy amber could be clarified apparently was known as early as the first century, for Pliny, in his Natural History, mentioned that pieces of amber were “dressed by being boiled in fat of a suckling pig by Archelaus, King of Cappadocia”. This is thought to be the first attempts at clarifying amber. It was Johannes Wigand, in 1590, who discovered other oils could be used rather than the “fat of suckling pigs”, and, by the end of the 17th century, methods of ridding amber of internal obscuration had been well established.
To produce a rich brown “antique” color, amber is imbedded in pure sand in an iron pot, then increasingly heated for 30 to 40 hours. The resulting rich brown color closely resembles the oxidized amber hues produced by aging. Such treated amber is often sold under the term “antiqued amber”.
An unheated autoclave or “pressure cooker” is used to drive the oil into air pockets of the porous material to produce clarification. Next, the amber is placed in an electric oven and gradually heated to soften it. During this stage, any air bubbles left within the mass of amber expand to form discoidal fractures. At the same time, heating speeds the process of oxidation and causes the amber to deepen in color. Oxidation occurs from the outside in, causing outer layers to be generally darker than the cores. The longer amber is heated, the darker it becomes. After porous pieces have been subjected to this treatment, they tend to be harder and more durable than they were previously. This process produces beautiful amber, in great demand by amber connoisseurs, and one which is still considered to be genuine amber. It is most commonly found in the finished pieces imported into the
USA and Western Europe.