Someone gave me a 7 gallon carboy, and it's got some dried stains in it, like liquid dripped down the inside and dried there. For the life of me I can't get it clean. Here is what I tried:
Soak for four days with bleach at .25 cup per gallon- no change.
Soak for four days with Star San at 1 oz. per 5 gallons- slight improvement, and the Star San got really cloudy.
Soak for two days with Oxiclean at 1 scoop per gallon- slight improvement.
(I rinsed very well between steps too).
Any ideas? The cloudy Star San leads me to think it's mineral deposits of some kind, but I'm not sure. The carboy has definitely been used to brew as it has gallon markings and a fermometer, but I have no idea what was in it previously.
Soak for four days with bleach at .25 cup per gallon- no change.
Soak for four days with Star San at 1 oz. per 5 gallons- slight improvement, and the Star San got really cloudy.
Soak for two days with Oxiclean at 1 scoop per gallon- slight improvement.
(I rinsed very well between steps too).
Any ideas? The cloudy Star San leads me to think it's mineral deposits of some kind, but I'm not sure. The carboy has definitely been used to brew as it has gallon markings and a fermometer, but I have no idea what was in it previously.