What is borax used for in jewellery making?
By Jared James · Last updated 21 May 2026
Definition
In jewellery making, borax is used as a flux during soldering, meaning it is applied to the metal joint before heat is introduced to prevent oxides forming on the surface as the metal warms up. Oxides would stop the solder from flowing and bonding properly, so the flux creates a clean, receptive surface that allows solder to run into the joint evenly. Borax is typically used as a powder dissolved in water or in cone form rubbed into a ceramic dish with water, and it is one of the most traditional and effective fluxes for silver and gold work.
Frequently asked questions
- How do jewellers use borax as flux?
- The most common method is to rub a borax cone in a little water in a ceramic dish until a creamy paste forms, then apply this to the joint with a brush before heating. It can also be bought as a powder and mixed to the same consistency.
- What does flux do in soldering?
- Flux prevents metal oxides from forming on the surface of heated metal, which would block the solder from bonding. It also improves the flow of the solder, helping it move into tight joints and sit cleanly rather than beading up.
- Can you use borax for all metals in jewellery?
- Borax works well on silver, gold and copper. Different metals and different soldering temperatures sometimes benefit from a purpose-made jewellery flux, so experienced jewellers keep more than one type on the bench.
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