Soldering is the process of fusing or joining two or more metal items together using a flux and solder and incorporating heat as the catalyst. But before you can begin soldering, there are several things to be considered. The design itself must lend itself to soldering, the parts to be soldered must fit closely and the correct solder and flux need to be used.

Hot Air Soldering

There are four basic types of silver solder, classified according to their melting points - ex-easy, easy, medium and hard. An easy grade solder will melt at a lower temperature compared to hard grade solder. Solder has to conform to the same hallmarking standard as the metal being worked upon, so Stirling silver pieces will need to be soldered using silver solder. The first thing to do before beginning to apply any heat to the piece is to ensure that it is thoroughly cleaned. The piece can then be annealed, which is the initial softening of the silver to be joined. Only the area that is taking the solder needs this treatment. A blowtorch at a temperature of around 1200 degrees F will suffice and as the findings heat up they will change in color to a dull pink.

Hot Air Soldering

Once this process has been carried out you can then apply the flux. This is a chemical cleaning agent that cleans the silver findings and the solder of any remaining oxide film and allows the solder to flow freely. The most effective flux is borax, which can be ground with a little water to form a paste that is then directly applied to the piece you are soldering. Check that there are no visible gaps between the two pieces of metal that you want to solder. As solder has a capillary action when liquid, any gaps between the two surfaces will allow the solder to run down one side of the seam and leave a messy finish.

Once the joint is coated on both faces with flux, you can then apply the flame to heat the item. A mixture of gas and compressed air is generally the best combination for torch soldering, as fine adjustments of the flame size and temperature are more easily obtainable. The flame shouldn't rest over one area but be moved constantly to prevent damaging the surfaces of the piece. If you have preplaced your solder at the joint seam prior to heating, once the correct temperature is reached the solder should flow into the joint. The alternative is to feed the tip of the solder (if it is in wire form) onto the joint where it should melt on contact and again flow into the seam.

Any flux residue can be removed by soaking the piece in hot water. If you find it difficult to remove the residue, soaking the piece in a solution of 5-10% sulfuric acid for a few minutes and then rinsing in hot water should remove any last traces. Do take into account any precious or semi-precious stones that are incorporated into the piece, as the acid (even at low concentrations) may affect the surface of the gem.

As with all hobbies that include the use of heat, make sure that your work surface is suitably protected and that you consider all safety issues before beginning your work.