Recently went to tone a print in Viradon and when I inserted the print (after it had been soaking in water for a few minutes) it start to 'fizz' on the print surface. I tried a few other prints and they fizzed so I mixed up some new Viradon (my working solution was quite old) and tried a few more... Still fizzed (and got uneven toning as a result). I've used this stuff several times and never had this problem. I've always mixed it using tap water but I could try distilled if that's thought to possibly be a solution. I tried both RC and GB prints and it happened to both. Ideas?