Make your own flux with Boric Acid and Denatured Alcohol
Boric Acid and Denatured Alcohol make a wonderful flux for preventing firescale on your work. These items can easily be found at your local grocer or hardware store.
Boric acid is also non-toxic for people, making it a great alternative to fluoride based fluxes. (Boric Acid is, however, toxic to insects - so can serve double-duty keeping your studio insect free!) Denatured Alcohol can be toxic if ingested, so do make sure to keep it out of reach of children and pets.
Spoon a little bit of the boric acid powder into a small dish. (It is best to use a dish with a tight fitting lid, such as a baby food jar, as the alcohol will evaporate quickly without.)
Add the alcohol slowly, mixing until a thin paste is made. Add more boric acid powder as needed to thicken. Getting the right consistency can take a bit of trial and error - I tend to prefer my flux a little on the watery side.
Brush on a liberal amount of flux over the entire surface, or, dip the entire piece in flux.
Place on soldering surface, and light with torch to burn off alcohol. It will produce a lovely green flame. Continue soldering and pickling as usual. Due to the flammability of Denatured Alcohol, it is best to store it in a secure area away from your soldering station.