Perhaps the grout is old and is peeling discolored or cracked then that is a good reason to remove grout.
Remove grout from bathtub.
Before you apply new grout around your bathtub you must first remove the old excess stuff that posed the problem in the first place.
Clean the surroundings of the bathtub.
If you want to replace broken tiles or just want a change is on such reason.
If this is the case it will be necessary to scrape it away.
Steps to remove the grout.
Remove and replace grout even the best tiling jobs show their age eventually.
Make sure the bit is the right size for the space between the tiles and adjust the bit to the proper depth.
How to remove grout.
When remodeling a bathroom or kitchen the hardest part can be removing the grout from pre existing tile.
Also grout and mortar are gritty and can scratch the polished surface of a bathtub.
One way to change grout color is to colorize existing grout.
Work slowly image 3.
If the grout is fresh it can be wiped with a sponge moistened with water.
When you grout bathtub tile you do so in order to protect the wall that is behind it from moisture but sometimes you will have to or want to remove grout.
The existing grout color is no longer pleasing to you and you wish to change it.
The old grout might be moldy and beyond cleanable.
Next rinse the area thoroughly and use a cloth to wipe the surfaces clean.
Therefore in addition to removing the mess from the tub your aim is to minimize any damage.
The water will soften the grout again allowing it to be wiped away.
If you see mold forming around where your floor and tub meet treat it with a mold killer after removing the existing caulk or grout.
Once a day has passed the grout will be cured and will no longer be removable with water.
When that day comes remove the grout and replace it to rejuvenate the installation and make the surface gleam.
This might include any grout along shelves corners and floor tiles or the grout and tile that surrounds the shower drain.
For much larger areas use a rotary tool image 2.
The blade is harder than the grout and will cut it away image 1.
Steps to repair grout around the bathtub.
Allow the paste to set for a few minutes to work its magic and then give the grout lines one more agitating scrub for good measure.
Grout and mortar are not water soluble so the soak and scrape method as you might do for drywall compound will not work here.
Let the area dry the area for the minimum of what the moldicide recommends which is usually at least 24 hours before applying new caulk.
For small areas use a grout removal tool with a carbide blade.
But the more effective way is to use entirely new tinted grout.