Brown stain from Prips

afternoon all,

I am getting a brown stain from prips flux that doesn’t come off in
the pickle. I made this batch of Prips flux last year and until
recently haven’t had a problem with it. It is possible, since I am
now using it on larger vessels rather than jewellery-sized objects,
that I just haven’t noticed any previous staining. Has anyone else
had this problem? Has my flux gotten too old or contaminated with
something? How does a solar powered fridge work? :slight_smile: