grout removal

Im replacing the tiles in my bathroom and i have cast iron enamel bathtub with old tile grout and mortar mix on the top edges. Ive tried using warm soapy water and a nylon brush but its not coming off.
Whats the best way to remove this old grout/mortar from the enamel surface without scratching it?
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Sleepy-Tom wrote:

There is a tool for this, its a grout scraper. It has a triangle head made of some kind of carbide and just about lasts forever. Be careful not to scratch the tub surface. I'm sure there is a cleaner but make sure it does not damage the surface.
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If soap and water would wash grout away it would have done so long ago. Grout, particularly the older stuff, is largely portland cement. Once it's dried and cured there isn't much that will cut thru it that wouldn't also damage the enamel on the tube. Your best bet is to scrape at it gently with a tool designed for this.
Another thing to consider is where your new tile and grout will fall. If it will cover the old, then I wouldn't waste the time cleaning it completely, just where it may interfere with the new installation
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I have no clue. I think, maybe, there is a special tool for grout removal. You might call a tile store.
Mark wrote:

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there is a special tool to remove grout but it involves scrapping of some sort. The tool you are referring to is like a small saw tipped in carbide grit its thin so you can abrade the grout between the tile and it will do a number on the tub.

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