A borax cone and ceramic dish set is the traditional way many jewellers make their own soldering flux, and it earns a permanent spot on the bench even if you usually reach for a premixed bottle. Instead of buying flux paste ready made, you grind the borax cone with a little water straight into the ceramic dish, so you control exactly how thick or thin the paste comes out.
Once you have a smooth paste, brush it over the solder joins before you heat the piece. This soldering flux stops oxidation and firescale forming on the metal while you work, so the solder flows cleanly into the join instead of pooling on a dirty surface. It is a traditional alternative to Handy Flux, and plenty of jewellers prefer it because the consistency is easy to adjust, from a thin brushed coat to a thicker rub for stubborn joins that need more protection.
The set works across silver, gold and most other solderable metals, and because you only grind as much flux paste as you need for each session, one cone lasts a long time on a home or studio bench.
