Hawzah News Agency – If the essence of an impure object changes in such a way that it transforms into a pure object, it becomes pure; for example, if impure wood burns and transforms into ash, or a dog falls into a salt marsh and transforms into salt [the ash and the salt are pure]. However, if the essence of the object does not change – for example, if impure wheat is turned into flour or made into bread – it does not become pure.
A clay pitcher or something similar that is made from impure clay is impure. As for charcoal that is made from impure wood, in the event that none of the former physical properties are in it, it is pure. And if impure clay is changed by fire into crockery or bricks, then based on obligatory precaution it remains impure.
An impure object about which it is not known whether it has undergone a transformation or not is impure.