Most months a new member posts a plea for help with soldering, so I thought I would summarise what they might need to know, particularly with reference to silver. Please feel free to post your add-ons and disagreements below. I must emphasise here that what jewellers do is not soldering at all, but brazing. However as they don’t seem comfortable with that, I shall stick with the time-worn usage.
Torches are sometimes listed as having a flame of a certain temperature, but that is not the whole story. It is important that the torch can provide enough heat for the job in hand. So while a small mini-torch is sufficient for soldering chains and thin rings, larger work such as heavy rings, bangles and brooches particularly in silver, will need a burner big enough to raise the temperature of the greater mass. There are many dedicated torches for jewellery, but if you decide on a hand held torch, such as the Taymar, or the GoSystem, from DIY stores the canister should say Butane/Propane mix. The size of the canister you choose will only make a difference to the available working time. For large items heat can also be conserved by making an enclosed chamber of several blocks. For silver and base metals it is not necessary to use charcoal, but some jewellers prefer it.
Strip solder comes in various grades identified by the width. Generally it is thinned by hammering or rolling to make it easier to cut and is then cleaned with emery paper or a Scotchbrite pad before clipping into small paillions. Some jewellers colour their solder with a waterproof pen to help identify any remnants later and this burns away harmlessly in use. The joint to be soldered must also be clean.
For hard or medium solder the joint is painted with borax or Auflux and paillions applied with a small brush also dipped in flux. When heated the flux tends to bubble and expand, sometimes called ‘flowering’. It then subsides, but the pallions do not return reliably and may have to be helped back with tweezers. This is less of a problem with Auflux.
Once the solder has been placed, the piece and the block on which it rests are heated in a circumspect way to allow the solder to dry out without too much displacement of the paillions. Then the heating is slowly increased, but the flame is not applied to the solder directly. Of the parts to be joined, if one is larger it is given more attention and the smaller one will heat by conduction. It is useful to work in subdued lighting to monitor the colour changes. The whole process may take 5-30 seconds according to mass of silver, but if nothing happens by then it is likely that the torch is too small , or that there is some contamination.
Solder once it has flowed and solidified will require a higher temperature to melt it a second time, so it is possible to use the same grade for 3 or 4 subsequent joints on the same piece. However as the work increases in size, it may be better to continue with medium, easy, or even extra easy solder , which require less heat. With the last two it is also wise to use Easy Flux, which becomes active at a lower temperature.
Many jewellers avoid either medium or easy silver solder as they find one or the other more difficult to use. Strangely there is no agreement on this, but I personally avoid the medium. It is a good idea not to trim or polish too close to a seam until all soldering has been completed, because polished solder joints may show as a groove when reheated. I shall not say much about paste solder which contains its own flux, because although it is very popular, particularly when working with wire, it is difficult to monitor the flow if hidden from sight, so that you might end up with an incomplete joint.
Personal tuition and the many free videos available online will clarify what no number of words can explain here. Dennis.