I have a little "kit" from Alpha Metals that I got years ago (and sadly,
I don't think they're available any more). It has a roll of silver-braze
wire and a tube of flux. Originally, the flux was creamy, but over time
it's gotten so stiff that I can't squeeze it out of the tube, plus, it
seems to have grown some crystals that make it hard to work with.

The flux contains potassium fluoride and potassium fluoroborate; is
there some way to "rejuvenate" it? I tried mixing some with a bit of
water, but that didn't seem to work so well.

Alternately, is there another easy-to-get flux I could use? I only
rarely need to silver-braze anything, so I don't need/want a gallon jug
of something...

thanks

Isaac