As used by Etsuko Makiyama at You Can Make It 2020 in her Filigree class - here is the Blue Flux - liquid flux for soldering.
Why do I use flux when soldering?
- Flux prevents oxides and firescale from forming - which can be a pain to remove
- It removes dirt and grease from the metal
- It helps your solder to flow easier, getting to where you want it
- Stopping oxides means your solder will bond the metal, giving you a solid joint, rather than bonding with the oxide which can come apart later.
Use flux when soldering to prevent oxides and firescale. Paint this onto the joint you are about to solder and it keeps your piece clean whilst being heated, allowing your solder to flow easily.
The Blue Flux acts as a cleaning and flowing agent. It dissolves oxide residues and inhibits further from forming. If you have a layer of oxide on your metal, the solder will stick to the oxide layer, creating a weak joint, which will likely come apart later.
Ingredients : Potassium compounds, Boric acid, Water, and others
Boiling temperature : 600-800 Deg.C.
Wow! This is a life changer for me. I have already demanded that all my jeweller friends get some :-) Much easier to use than a borax cone, the solder flows easily and the metal (silver in my case) stays beautifully clean.