That's a very nice looking tank. And quite economical too!, after doing some searching, I found it here.I etch my boards in Sodium Persulfate using an economy etcher. Using this etcher has greatly reduced my consumption of sodium persulfate. I can etch three times the number of boards for the same amount of sodium persulfate as compared to using an unheated tray. It is a lot faster also.
Question, how many PCBs can you process with 1 Kg of sodium persulfate? In other words, how many litters of sodium persulfate solution do you get out of one std bottle of crystals?