Bakers is a popular tried and true range of soldering fluxes.
Bakers fluxes are designed for use with a range of solder alloys and base metals
Bakers Soldering Fluid
A general purpose flux for soldering, copper, brass, tin plate, tinned metal and clean steel sheet.
Bakers Solderine Paste Flux
For use when a fluid is not practical in soldering copper, brass, small tinned parts and for electrical work.