Surfaces to be soldered must be shiny bright - if you're not a regular solderer (forgive me if you are) the most common mistake people make is too much solder and not enough heat.
Peccavi
May 2009
No, brass, like similar non ferrous metals of that type, will take 'normal' fluxes like Fluxite, Bakers soldering fluid, Sifbronze etc. You can also use traditional solders such as electricians multicore or plumbers tin/lead alloy or lead free. Make sure everything is spotlessly clean and you can solder brass to copper, steel etc - but not aluminium, naturally.
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