Gold is a precious metal that is frequently featured in jewellery, as well as in other fine decorative objects. Jewellers and craftspeople often melt gold to cast or otherwise reshape it into new forms. To properly melt gold, you must have a basic knowledge of its composition and melting point, as well as the right tools, equipment and technique.
Understand the Composition of Gold
Gold comes in different carats; these include 10, 14, 18 and 24. Gold also comes in different colours; these include red---also known as rose---green, white and yellow. Different carats and colours of gold contain different metals. In fact, the only type of gold that is pure---that is, it contains no other metal but gold---is 24-karat yellow gold. Eighteen-carat yellow gold also contains silver and copper, while 10-karat yellow gold contains silver and copper in greater amounts. Green gold contains gold and silver, while red gold contains gold and copper. These differences in composition explain why different types of gold have varying melting points.
Knowing the Melting Points of Gold
A melting point is the number of degrees Fahrenheit at which gold melts. The melting point of gold depends on its composition or type. For example, 18-karat yellow gold has a melting point of 927 degrees Celsius. Fourteen-carat yellow gold has a melting point of 879 degrees Celsius. Ten-carat white gold has a melting point of 1079 degrees Celsius. As you can surmise, the more pure the gold, the lower the temperature required to melt it; therefore, it takes longer to melt gold that is mixed with other metals.
Using a Crucible to Melt Gold
A crucible is small, dome-shaped container in which metal is melted. A crucible is highly refractory---that is, it reflects a lot of heat back onto the metal. Before melting gold in a crucible, you must make sure the crucible is clean so that your gold does not become contaminated. Also make sure that the crucible's pouring spout is open, as you will likely be pouring the melted gold into a mould of some sort.
Types of Torches for Melting Gold
To melt gold, you require a torch that reaches a sufficient temperature. Butane torches, propane torches and oxyacetylene torches are all good choices for melting gold. A butane torch can reach a temperature of 0-3.889 degrees Celsius. A propane torch can reach a temperature as high as 1982 degrees Celsius. An oxyacetylene torch, which is also referred to as an oxy-gas torch, combines acetylene with oxygen, and gets as hot as 3482 degrees Celsius.
Other Supplies Needed to Melt Gold
You also need flux---a substance made of borax that helps melted metals to flow better---and a stirring rod--a rod made of glass--with which you can stir the gold as it melts.
Basic Technique for Melting Gold
Once you have placed the gold that you want to melt in the crucible, add a pinch of flux to it. Then light your torch and adjust the flame so it is neither too low nor too high. Apply the flame directly to the gold and try to keep the gold completely covered by the flame from the torch as you are melting it. Use the stirring rod to move the gold as you melt it and determine its state. Melt gold as quickly as possible and pour it into a mould as soon as it is melted.