Most of CPM’s clients will cut their teeth in the jewellery manufacturing trade by working with silver, and a great deal of these jewellers will opt to stick with this versatile, affordable and accessible material rather than branching out into the world of goldsmithing (and all the regulatory red tape associated with that precious metal). Soldering, annealing, and torchwork will form a major part of this craft, so it’s crucial to hone your skills so you can wield heat and flame with confidence.
KNOW YOUR SILVER SOLDERS AND PREVENT THESE COMMON SOLDERING ISSUES:
Silver solders are alloyed with fine silver, copper, and zinc in various ratios according to the type. The more zinc used in the alloy, the lower the melting point will be. CPM supplies the following silver solders:
- Extra Easy silver solder: 665 – 700ºC
- Easy silver solder: 705 – 725ºC
- Medium silver solder: 720 – 760ºC
- Hard silver solder 745 – 780ºC
Common soldering issue 1: Oxidisation:
The copper within the sterling silver (up to 7.5%) and in the solder (up to 22%) means that it tends to oxidise, and this discolouration is usually most pronounced on areas that have been exposed to extreme heat. Though surface oxidisation is easy enough to remove with a polishing cloth or by using salt, baking soda and foil trick, prevent this extra work by avoiding the following, which will exacerbate oxidisation:
- Acidity (this is even influenced by the PH balance of the jeweller’s skin)
- Exposure to ammonia or bleach
- Exposure to hard water
- Every day wear and tear (advise your customers of this so they car care for their silver items properly)
*The salt, baking soda and foil trick involves mixing equal parts salt and baking soda in aluminum foil and pouring in boiling water. Any sterling pieces placed into this mixture will emerge clean and free of surface oxides, however do note that certain gemstones or pearls may be fractured through heat shock by the boiling water – so avoid this technique for jewellery that contains these materials.
Common soldering issue 2: Firescale
Firescale occurs as a result of the actual metal being overheated and can be tricky to prevent for the novice solderer. Because it’s an oxidisation of the alloys deeper within the mass of the sterling silver, you can’t simply it buff off, as is the case with surface oxidisation. It’s particularly frustrating since this unsightly blemish can make it’s appearance after the polishing phase of what you think is a perfectly finished piece. Always check your silver jewellery pieces for firescale under strong light on a sheet of blank white paper, which will help the discolouration become more obvious. Elbow grease is the only fix, and be prepared for several rounds of sanding and polishing depending on the depth of the oxidisation. To avoid firescale:
- Use charcoal blocks for soldering and annealing: When charcoal is heated, oxygen is removed from the proximity and the alloys inside the sterling silver don’t get as much of a chance to oxidize. Charcoal blocks also reflect heat back onto the item, decreasing the amount of time it takes to anneal or flow solder, which is especially useful for large pieces.
- Use Borax/Boric acid and alcohol or a self-pickling flux: Before working with heat, create a protective barrier around your silver jewellery item by coating it with a mixture of borax or boric acid and isopropyl alcohol. This technique also works for other precious metals. While it does help to prevent a firescale headache, the tradeoff here is perhaps extra pickling time needed to remove hardened borax, but you can also try using a self-pickling flux.
- Ensure every piece is thoroughly pickled after exposure to heat in an acid-pickle to remove as much surface oxidization as possible.
Common soldering issue 3: Pits
These pockmarks in the solder seam occur when the zinc within the silver solder burns away as a result of overheating, as the silver solder rises past its boiling point. This is a double red flag, since the zinc’s incineration causes the melting temperature of the solder to rise, which makes it even harder to get a good seam.
- If you run into this issue the recommended course of action is to immediately down tools and remove the oxidisation and flux by pickling or cleaning and try with a fresh solder rather than accidentally melting the jewellery item.
Common soldering issue 4: When that solder just won’t flow
- Dirty metal is one of the most common factors that hinder the flow of solder. Silver can be dirtied by oils on the hands, polishing residue, old flux, oxidization or any variety of contaminants, and further strengthens the argument to always clean your silver with boric acid and alcohol, and thoroughly pickle before soldering.
- Solder may also not flow well if you’re not using the appropriate size of flame for the item. This knack comes with experience and practice, and getting it just right can make or break a soldering or annealing task.
- In the case of sterling silver, the entire piece must be heated evenly throughout to get solder to flow nicely. This is done by first heating the whole piece to annealing temperature, then by focusing on the specific soldering area and alternating between those two until you see your solder flow. It’s a balancing act since a pointed, harsh flame can cause firescale, so take care to set your torch to produce a bushy flame that can evenly heat the piece without scorching the metal.
ANNEALING YOUR ITEM TO MAKE IT MORE WORKABLE:
As we manipulate and shape sterling silver, it gets ‘work hardened’ as the molecules within the metal get condensed. Annealing removes these internal stresses and renders the metal more malleable, preventing it from snapping or cracking as it is subjected to bending and hammering. Sterling silver should be evenly heated to 593ºC and immediately quenched in water. Then submerge the item in a pickle-acid solution to remove surface oxides and leftover products.
- As with soldering, take care to control the heat and reach the accurate annealing temperature to prevent firescale. Using a large, bushy flame and making use of a charcoal block will heat the piece evenly and avoid oxidisation.
Indicators that the sterling is annealed:
- Colour is a crucial indicator of this process, which is enhanced by working under slightly dimmed light or the shadow of a fire brick. As it heats up, the surface of the metal will change colour until a dull red hue is achieved, at which point it should be immediately quenched in water. The longer this dull red is maintained, the closer you get to the metal’s melting point. While sterling silver is rather forgiving, if you overheat it to cherry red you’re dangerously close to turning your jewellery item into a melted mess.
- Permanent marker may also be used to determine when your piece of sterling silver is at the correct annealing temperature. Mark the metal in several places including the thickest and thinnest parts of the item. As you heat sterling towards its annealed temperature the permanent marker begins to fade, and when it disappears this indicates that the piece is fully annealed.
- Paste flux can be used in the same manner as permanent marker. It too should be placed on the thickest and thinnest part of the piece, and upon annealed temperature being reached, the flux will turn glassy and clear.
FINAL TIP:
A common error we at CPM have noticed is that our jewellers who often manufacture with gold forget that silver has different working properties and tend to overpower the metal. Also remember when working with open flames to always observe proper safety protocols, have a fire extinguisher at the ready, use protective equipment and keep your workshop well ventilated.
CPM supplies sterling silver (925 silver), fine silver and Argentium silver and a full range of raw materials including gold, platinum and palladium to manufacturing jewellers across Southern Africa. Our well-trained staff are available to answer your questions about soldering and heating, as well as a host of other topics related to jewellery fabrication and associated products and services.
