I am trying to clean the IC40 with acid like I normally do except this time I am not getting bubbles nor is the scale being removed. I bought the acid yesterday and got pretty strong fumes when I opened it, so it seems pretty strong. Can acid go bad or get weak if it is an old bottle? It's the same brand and strength (31.45%) as I have used in the past. Maybe I will get a different one tomorrow and try that.