The 6 Golden Rules
The metal. Always make sure the area which you wish to solder is clean, dry and free from grease. If necessary clean the area with a solvent (MEK, Mek Pak, Plasticweld or generic equivalents). The area must also be bright ready to take the solder. Abrade the metal so that there is no oxidisation present. Use a scratch brush, emery cloth, fine wire wool or an abrading rubber (eg Gariflex block) to bring the metal up bright and shiny.
The soldering iron tip should be clean, free from scrag and tinned with a layer of fine solder. Use Tip Tinner and Cleaner to keep the tip well covered and bright.
Use the correct melting point solder for the job. All solders, except 70o, will adhere to non-ferrous and some ferrous metals.
- 70o solder for white metal. This is not really a solder but a metal called Cerabend, which is used by plumbers when they are bending copper pipe to prevent the pipe collapsing or cracking. It is easily melted in hot water. Use with a low temperature iron (preferable) or a standard iron with a dimmer switch or light bulb in circuit.
- A point to remember – 70o does not successfully adhere to non-ferrous metals but will readily adhere to all solders, so when attaching white metal parts to, for example, a loco frame, thinly tin the frame metal with, for example, 145o first, then use the 70o to make the joint between the white metal part and the frame.
- 145o used to solder smaller detail. The is solder sometimes contains an amount of cadmium so do not breathe in any fumes and use in a well-ventilated space. This goes for all solder fumes.
- 188o and 296o used for main joints. Solders of higher melting points can be used when a stronger joint is required, for example with larger-scale loco frames.
- High temperature silver solders (620o, 630o etc) require a blow lamp or torch and are quite another process!
Use the right flux for the metal. Most non-ferrous metals can be soldered with either commercial fluxes (Carr’s etc), dilute phosphoric acid of various strengths or a cream flux like Powerflow. After finishing the job, the work should be washed with a solution of warm water and 10% spirit (meths, surgical spirit) or a small amount of bicarbonate of soda in water to give you an alkaline solution. This will neutralise the acid in the flux and stop it working.
Use a hot iron. However, turn the iron off when not using it – ie if you are not going to solder in the next five minutes or so. If you don’t, you will cook the bit and eventually coat the tip with scrag and have to do a complete re-tin or get a new bit. The iron will return to temperature within a minute or so when turned back on, so any delay in working will be very slight.
Get in and out quickly. With a hot iron get into the job, get the solder flowing and then get out. If you leave the iron on the job too long you may un-solder any nearby joints or cause the solder to spread too far.
Practice first on pieces of scrap before starting on a model. Then, when your confidence has increased, start on something like a simple etched wagon kit. And if the job just isn’t going right, stop, turn off the iron, go and have a cup of tea and try again later.
Soldering has its dangers. The iron tips are very hot and can cause quite serious burns. Solder contains heavy metals, which you should avoid ingesting – so, don’t eat, drink or smoke at the bench and wash your hands thoroughly before eating. Avoid inhaling any fumes, especially from 145o solder. Oh, and if you drop the hot iron – don’t try and catch it! It hurts like hell when you catch the wrong end!
Observe these simple rules and guidelines and you will solder successfully.