Electric soldering iron and gas blowlamps are generally the heat sources required for soldering, these days you’ll find that the flame-heated soldering iron is hardly ever used.

When choosing the right tool for you then it’s worth considering that attempting to solder with a tool that simply doesn’t have the power for the task in hand will just result in a waste of time. On the other hand, if it is too powerful it will make the solder far too hot and this weakens the joint. If your project involves particularly delicate work, then the odds are you you’ll need an electric soldering iron. Some models of gas blowlamps are also quite proficient.

If the electrical job is quite large, or you are soldering jewellery or model-making, then consider using a blowlamp with a fine or extra fine burner as this will produce a hot flame that can be kept to a minimum. If you need it to contact with a larger area then you’ll need one of the more powerful soldering irons. If the project involves plumbing, such as soldering capillary joints, then a gas blowlamp or blowtorch is the best option, whereas large pieces of metal, (or brazing), will require a powerful blowlamp.

Consider the following points:

• The solder and joint both have to reach a temperature of 250°C before it melts, this has to be maintained throughout until the job is complete.

• Consider the thermal size of the joint and its direct surroundings as large joints call for a larger supply of heat to reach the right temperature. Also when soldering metals, such as copper which is a good conductor of heat, to maintain a high temperature a steady source of heat is necessary.

• Take into account where the joint is positioned. If it is close to temperature-sensitive electronic elements like transistors, then it’s advised to add a heat sink between the joint and the component which will soak up the heat from the soldering and stop it from travelling. Place a large pair of pliers between the two points as the heat sink. However, if the joint covers a large surface area and is open to the elements, it could radiate the heat away too rapidly. Fix this by surrounding the joint in a provisional brick hearth, or covering part of it in ashes. On no account place the joint on a surface that is a good conductor.

Brazing is a process which utilizes alloys of copper and zinc as they melt at much higher temperatures than solder (700 to 800°C) and provide stronger joints, and a special flux or a borax paste is required. Braze (or bronze) welding uses the same type of alloy, but a fillet is built up on the surface rather than running it into the joint. In the case where the joint is only small, then it’s possible to reach the necessary temperature by applying a gas blowlamp flame directly on the joint. If this doesn’t work, a higher heat supply is needed.

You can get a brazing attachment to use with an arc welder, generally in the shape of two carbon rods fixed in a hand-held clamp. An arc is produced between the tips of the two rods, and the resultant flame is used to heat the joint.

Before using this method for any repairs it’s best to practice as it is an extremely powerful and fierce supply of heat.

Oxy-acetylene welding equipment is regularly used for brazing as the heat can be simply controlled by using the correct size nozzle and the torch is straightforward to control. However, a big problem with this method is that the gases are quite difficult to get hold of.