Ceramic Tile Grout Cleaning

Submitted By
Nancy Wiltzius
0 expert, 1 community

My well-meaning son put a preservative on my white bath tub tile. The preservative turned yellow when it dried. Is there anyway to clean it off without completely removing the grout and redoing it? I don't know what the preservative was, it was done years ago. I have been scraping it off the tiles themself since then. I am down to the grout now, but scraping is also removing grout.

Thanks, Nancy