My Son-in-law Tiled His Bathroom Floor And Did Not Wash The Grout Off The Tiles When He Was Done. Consequently, It Hardened. I'm Wondering Whether There's A Solvent For This Hardened Grout. The Tiles Do Not Have A Smooth Surface, But Rather Many Small Depressions And Grooves With The Hardened Grout In Them. Thank-you.

Flickit

Have you tried scraping a small obscure area with a plastic or even metal paint scraper?

TerryB

The only thing that will come close to removing groute is muriatic acid. This will work for a very light or haze of groute. Anything thicker and you are out of luck.

Shanni4

I did the same thing when I ceramic tiled my shower walls. It was awful. I don't know what I was thinking letting it sit there like that. My husband bought me a dremel tool with a stone grinding wheel. I had to grind off the dried grout. It took a while but it all came off. He bought it all in a kit for about $40. Hope this helps.