Haa....... we had a job very similar some years ago. We made I think 30 or 40 signs and they installed them in various parts of this food manufacturing plant. They tried cleaning them, before they went up and knocked half of the ink off before they were hung. They wanted me to refund the money. I asked, why are you power washing signs at close range before they even go up ?? Our cleaning crew wanted to make sure they'd withstand our stringent cleaning routines and your signs failed. I said, where or when did you ever tell me, they were to be hit with power washers and so often ?? We didn't. Then, we didn't do anything wrong under normal circumstances. So, to fix this problem, we will get all new blanks, but clear and print it backwards and overlay a piece of white. Then, your washers can spray the livin' sh!t outta them and they'll be fine. We charged them over to do the new methods and knocked about 15% off. They were happy and so was I. If people would discuss their needs in its entirety, things go so much better all around. Not only that, but we got 2 or 3 cases of pies and cakes after it was over.