Very good question, Frank. I asked my buddy to whom I gave the magazine, to check the article but unfortunately it does not say anything one way or the other about washing after the staining. We could conduct a scientific test about this. 1/2 of those who get my postcard should re-wash it to neutralize the acidity of the tea, and the other half should not. In 10 and 25 years down the road we'll check and see if there is any problem with the unwashed ones.