Old Slate Floor needs major repair
Anyone have any suggestions how to clean up and repair the grout lines in an old slate floor? I had one floor cleaner professional remove the polyurethane or whatever is on the floor in one small section before he realized it was going to take a lot more work than we estimated. The removal is one thing, but how to repair/renovate the grout lines is another. There is all kinds of efflorescence and chips/holes in the grout lines. The floor guy says it was an old "mud job" with the slate laid into it.
Here are the pictures of it where you can see the before and after removal:
Is this something that can be repaired? I hate to have to seal it all up and put another floor over it. All that mixed slate has so much character and it would look marvelous with clean lines after it has the shiny surface removed.
Any suggestions would be appreciated!