Experienced jewelers and manufacturers know that typical “cold soldering” is more accurately described as “resistance soldering.” Cold soldering tools, like the popular ColdHeat Soldering Pen, have a split-tip with an electric current running through each point. When the tips are touched to solder, the probes and the solder heat up very quickly because of their resistance to the current passing through them. Lifting the tips away from the solder breaks the circuit, and everything quickly cools.
Now, what if you could use a similar technique on any metal – even ones with very high melting points like gold? Materials scientists at Iowa State University may have just revolutionized the manufacturing industry by developing a soldering method that requires no heat or electricity. It works by forming a shell around microscopic metal droplets and keeping them in a liquid state – even when their surroundings are cooler than their melting temperature – until the shell is ruptured, causing the metal to flow and solidify, like solder.
first things first, we’ll establish the difference between soldering silver and soldering gold jewelry. One of the key differentiating factors is temperature. Both gold and silver solder comes in a range of temperatures. Silver can be found in four different types, easy (E), soft (S), medium (M), and hard (H), each with different flow temperatures. On the other hand, gold can be found in many more forms. You’ll have to consider the carat, ranging from 8 up to 22, and also the color, white gold, yellow gold, and red gold. Here’s a breakdown of the melting points for soldering gold jewelry:
Solid metals have a crystalline structure, so melted metal is subject to the physics of supercooling. The researchers at ISU created the above-mentioned droplets by whipping molten metal into a froth, then allowing it to cool gradually. Oxygen in the froth causes the very outsides of droplets to form a thin metal oxide shell. This oxide reacts with acetic acid, forming a smooth oxide-acetate shell that allows the core to stay liquid as it cools. This ultrathin shell prevents the liquid metal from coming in contact with nucleation sites needed to trigger solidification. Rupturing the shells causes the liquid to flow and immediately solidify, bonding surfaces together – kind of like a water balloon filled with super glue. In a demonstration, the researchers used the technique to solder a gold wire to a sheet of gold film, repair holes in the silver film, and bond sheets of foil together.
Let’s dive into our step by step guide on how to solder gold jewellery.