Soldering is how metals are attached: joining similar or dissimilar metals using solder and heat. Solder — as a noun — is small pieces of metal alloy that melt and flow at a lower temperature than the metal of the parts being joined. It acts, in the course book's own words, like a glue to hold a piece together.
Three grades, one logic
The metalsmith generally works with Hard, Medium and Easy solder, in gold or silver. The harder the solder, the higher its melting temperature — always below the parent metals' melting point, but higher than the easier grades.
The reason for keeping all three in clearly marked, separate containers is sequencing: use hard solder for the earliest joints, then step down through medium to easy. Each later soldering session then melts only the new solder, never re-opening the joints already made. A complex piece can go through several firings intact precisely because the grades descend. (The family extends beyond the big three: extra-easy for repairs and final joins, very hard for enamelling.)
Flux: nothing flows without it
The word comes from the Latin fluxus, flow — and that is the whole job description. The temperatures that melt solder would instantly oxidise the metal surface, and oxide blocks flow. Flux acts as an oxygen inhibitor so solder enters the joint smoothly. It comes solid, powdered, pasted or liquid; borax powder, mixed into a paste with water, is the jewellery-supply-store classic — long-lasting and cheap. Commercial fluxes blend borax and boric acid with fluorides and potassium salts.
Technique at the torch
- The pieces to be joined must be clean and in perfect contact. Solder can never fill open spaces — a gap is a design flaw, not a soldering problem.
- Flux always. Without it the solder will not melt and flow.
- Heat the whole piece evenly, then bias slightly toward the joint — solder is drawn toward the heat, so the joint area guides the flow.
- The moment solder has flowed evenly, stop the heat. Wait a few seconds, quench in water, and soak in pickle to clean.
- Clean, unused solder always melts before already-melted solder — useful when touching up a joint.
Reticulation: the deliberate overheat
Reticulation adds surface texture to silver or gold by deliberately overheating it, producing a rich, somewhat random texture. Throughout the process the metal sits at the edge of melting — it may actually melt through and form holes, and the course's advice is to incorporate them: they only add to the haphazard effect. It is the one place in metalsmithing where losing control is the technique.
Fusing: no solder at all
Fusing takes gold or silver pieces to the approach of their melting point, so the outer surface liquefies and the pieces join directly — no solder, a very organic, rough feel, and, in the course book's phrasing, great fun with scrap off-cuts. The rule from soldering carries over unchanged: the pieces must be clean.
Grounded in the JDMIS Metalsmithing (MS100) course materials. Learn the torch hands-on in Foundation Metalwork Skills and Experience and Intermediate Techniques and Stone Setting. Related reading: Annealing and Pickling Silver and Precious Metals and Hallmarks.