I have a pair of Polish Pickle Pots, something like this:
But when I use them, I am yet to get good results. Mainly I've tried using them for sauerkraut (maybe 6 times), pickled beetroot (once) and miso (once). But always the content goes mouldy.
Even with plenty enough brine from the content, and the stones hold the cabbage below the brine level, then the stones themselves go mouldy (black mould).
Is there something I'm missing? My pickles in plastic, with water-filled bottles or other plastic bags as weights never seem to have the same trouble.
Is there a special technique for using these pots? Is it mandatory to fill the air-lock around the lid (I do)? With water?