Testing for isotopes can have limitations. What if the forger gets hold of pre-war paint, or purifies paint personally, or forged the painting before atomic te

Testing for isotopes can have limitations. What if the forger gets hold of pre-war paint, or purifies paint personally, or forged the painting before atomic testing? I don't know how viable or common these methods are, but they could make this testing process less useful in the future. Of course, identifying fakes between 1945 and 2008 is still an awesome contribution.