Gold is one of the most expensive elements in the world and is well known for its use in jewellery. Old gold jewellery can be recycled by melting it down, making it available for use in other applications. There are several different methods to melt gold and these should be carried out by a professional.
Physical properties of Gold
Gold is a metallic element that has the atomic number 79. It is a very good conductor of heat and electrical currents, which is why it is frequently used as wires on printed circuit boards. Gold has a very high melting temperature of 1,062 degrees Celsius (1,943 degrees Fahrenheit). This means that the melting of gold can only be achieved with flames that reach this temperature.
Propane is a combustible fuel that consists of 3 carbon atoms and 8 hydrogen atoms. It is typically obtained in small cylinders, and is used for a variety of applications, including cooking and heating. The maximum flame temperature that can be obtained with propane gas is 1,979 degrees Celsius (3,595 degrees Fahrenheit). This is hot enough to heat a crucible and melt gold.
Melting Gold with a Torch
Melting gold should be carried out by qualified personnel that have the necessary safety wear. The gold is placed into a crucible, which is a container that can withstand temperatures above the melting point of gold. Crucibles that are used to melt gold are usually made of graphite. The crucible is placed upon a fireproof surface and a torch is directed at the gold within the crucible. The gold should melt within a few minutes.
Melting Gold Alloys
24-karat gold is 100 percent pure and does not contain any other metallic elements. Gold items below 24 karat are not pure, and contain a small percentage of silver, copper or zinc. The addition of these elements changes the melting point slightly, which means a propane torch should be able to melt lower purity gold more quickly. For example 18-karat gold has a melting point of 926 degrees Celsius (1,700 degrees Fahrenheit) and 14-karat gold has a melting point of 879 degrees Celsius (1,615 degrees Fahrenheit).
- Lenntech Water Treatment Solutions: Gold
- Engineering Toolbox: Gaseous Fuels and Chemical Composition
- Propane 101: About Propane - Characteristics, Properties and Combustion
- Gold Gazette: How to melt gold
- United Precious Metal Refining: Tips on Using the Handi-Melt Type Electric Furnace for Casting Gold and Silver Alloys
- Electrical Engineering Portal: Resistive Heating Explained in Details
- "Complete Metalsmith: Professional Edition"; Tim McCreight, 2004
- Zedcor Wholly Owned/PhotoObjects.net/Getty Images