It should tell you in the instructions. I just finished one with grid lines and all the stamped bits disappeared as soon as I gave it a gentle wash. My instructions said to make sure you don't get the aida wet until you have finished. i'm very happy with the results.
Enjoy your cross stitching 
Not really a scam or fraud, but I wasn't sure where else to put it.
Has Trump completely lost what was left of his mind?


