Can you tell me what is the best thing to use to clean the grease out of a grout joint in the kitchen floor.
I have to re-grout some areas of the hotel kitchen quarry tile floor. I've tried vinager and water, but the new grout does not seem to adhere well.
What is the best way to do the job

I would use a good grease cleaner first. Even a good dish soap works well. Then use a powder grout cleaner for the grout. Now don't skimp on the grout cleaner, it wont be worth your time. A cheap grout cleaner is worthless. Once you mix the powder with hot water apply to the grout, let sit a for like seven minutes then scrub with a brush, I like to use a good nail brush.

Now your grout is all clean and dry and your ready to re-grout. Where you still have some grout and that grout is close to the top using a thin mix of grout would be better, using a feathering technique. You can also use a acrylic additive to the grout instead of using water. However you must make sure you remove this from the tile otherwise it will be very hard. Think of the acrylic as adding glue to the grout.