General Tips for Grout Cleaning
Clean the grout first with water and allow to dry. This will remove any loose surface debris.
Never use bleach on colored grout, as it will discolor the grout.
Use a stiff brush for scrubbing. Old toothbrushes will be too soft. Also avoid using metal bristles, as they will wear away the grout.
If you're using commercial cleaners, bleach, or other chemicals, make sure the room you're working in is well ventilated.
Use gloves and protective eye wear when working with any chemical-based cleaners.
Test your grout cleaner on a small, inconspicuous area first to make sure that it won't erode or damage your grout work. This is especially necessary if your tile grout is old or damaged.
Never mix cleaners together! Chemical reactions can cause noxious fumes or burns if the mixture touches the skin.
When your tile grout is completely clean, keep it looking fresh and new by applying a coat or two of grout sealer. There are various types of grout sealers available for different uses, such as floors or bathroom tile. Make sure you purchase the correct type for the grout you'll be applying it to. Reapply the grout sealer at least once a year, or more often if necessary.
Hope this helps!!! Have a good one.