Recently we have finished project where we stripped old, topical sealer off, diamond honed, powder honed and seal 740 sq ft of limestone. We used solvent based, impregnating sealer from SCC and floor machine to apply 2 coats. We also supplied SCC marble cleaner and explained in detail how to clean the floor.

Now, week and half later, customer is complaining that the project did not solved his main concern that floor will be protected from the spills (not the etch marks). As an example he splashed water onto the floor and even thou water bubbled on the surface, limestone got a lot darker. His reasoning is that if stone gets darker, means not completely sealed and will stain when something else gets spilled, like oil, wine etc. He agreed that being a limestone, porous by nature, even pouring gallons of sealer may not completely seal the stone and rejected my offer to seal the floor with another coat of sealer. He agreed that the floor looks a lot better but since part of that floor is in the kitchen and dinning room and impossible to prevent accidental spills, it will stain. As of another example, he showed new, oily stains next to the fridge and poured and wiped off red wine onto the floor which also stained. He fills that he spent a lots of money for nothing and he wants to get his money back because the stains are not cleanable.

How to explain, why the sealed limestone gets darker when wet? I always want to lower the expectation and over deliver the results but here I need some counter arguments to repel his insane request and general guidance of what to say to this these type of requests in the future. Returning of money is not an option. What should I do?