Differences between melting and casting
Although they may seem the same, melting and casting gold is not the same. When we melt gold we do it with the objective of heating the valuable metal until it is left in a liquid state to make ingots and so on. On the other hand, melting gold responds to a more complex process that removes impurities through the application of heat, pressure, and other chemicals.
Once this is understood, we can go on to explain how gold is melted and why. Today, it is known that around 6000 BC, this process was already in use in cities such as Babylon (Mesopotamia). There is also other evidence that indicates similar processes in Egypt or China.
As we can imagine, gold was extracted in the past in very simple ways, it was crushed using tools and using force, and then the impurities were removed with water. Later, clay ovens were used for smelting. Evolution and technology have shaped this process to what it is today.
Gold smelting process in the lab
The steps to be followed in the gold smelting process are as follows:
- Processing: It consists of separating the materials from the rest of the useless material. Pressure is used to pulverize the gold ore, which remains in fine particles.
- Smelting: These fine particles are heated in a furnace which must be at gold melting temperature, which are 1064℃. Although most of the excess material is removed here, some remains.
- Pre-melting Chemical Removal: Gold may contain some hazardous chemicals. Therefore, we must dispose of them prior to melting. Some of these elements are mercury or iron.
- Removal of impurities: There are still some impurities that need to be removed. We are talking about metallic elements that must be eliminated with potassium cyanide, which separates gold into small nuggets.
- Melting: We put the gold back into the furnace to melt the gold and make ingots with it.
- Here you have the video of the first melting in the lab, in our own furnace, the effort and work is materializing!