Details below of a Grout colouring job I recently completed at a house in Morecambe. In this instance, the grout had become stained, and my client was no longer happy with it.
There are a number of reasons grout can lose its appearance including the build-up of mould in damp and unvented areas, staining from liquids accidentally spilt on the floor and surprisingly if you have a coloured grout it can lose its colour due to the bleach found in common types of household cleaning products. Grout contains lime which is acid-sensitive and will react to acidic cleaning products so for general cleaning do use a pH Neutral Cleaning product.
To tackle the stained grout I first tried Tile Doctor Pro-Clean which can be used at different levels of concentration to increase its potency. In this case however when this grout dried it went back to being patchy so then the only answer was to restore its appearance using a Grout Colouring kit.
Grout Cleaning and Colouring
To form a better bond with the Grout Colourant I first treated the grout with a Tile Doctor Pre-Treat Cleaner, which is very slightly acidic and effectively etches the grout. If you have a particularly acid-sensitive stone tile (Limestone, for example), it is recommended to use Tile Doctor Oxy-Pro cleaner instead as this won’t upset the stone, yet still clean the Grout ready for colouring.
Once the Grout had dried (which is some cases can be several hours), I applied a thin coating of the Grout Colourant, as a thin coat dries quicker and provides a more even finish. A second coat was then added, before polishing off the excess from the edges of the tiles. After about half an hour the Grout Colourant was dry to the touch (at this stage you should be able to walk on the floor). Note that if you are Grout colouring a wall tile in a shower cubicle, it is best to leave the area for 24 hours before using the shower.
As you can see from the photographs, the result was very effective, and needless to say my client was very happy with the rejuvenated appearance of her grout.
Source: Grout Stain Cleaning service in Lancashire