Removing grout haze that is adhered to a tile floor can be difficult. The type of tile greatly affects the difficulty of grout haze removal; also, if the grout was polymer modified, it may be more difficult to remove.
In general, the more porous the surface, the better grout will adhere. Conversely, grout haze is more easily removed from dense impervious tiles (e.g., porcelain).
To remove the grout haze, start with an alkaline cleaner and a nylon scrub pad. Make sure to check that the scrub pad is not damaging the tile. Normal floor tile will not be affected by a using a scrub pad, but some decorative tiles do not have the same surface hardness. It is best to test first in an inconspicuous area.
If the scrub pad is not effective, there are specialty cleaners on the market that chemically attack the grout haze. Typically these are weak acids. As with all acids, follow the manufacturer's warnings carefully and use caution. Always check the tile in an inconspicuous spot first in case the cleaner affects the tile.
Again, these specialty cleaners will not affect most floor tiles; however, it is prudent to check.
Some tile installers use stronger acids that they carefully dilute. While experienced professionals can do this, there are great risks in doing so. There is the possibility of bodily harm as well as damage to the surroundings.
Changing grout color is more commonly done, but again, the results are generally not as good as the original. The color in grout, unlike tile, comes from liquid-dispersed pigments. Obviously, these are not fired but rather become part of the cement's matrix. Grout is usually colored with an epoxy paint made for this purpose and sold in tile shops. When the grout is new, has not been sealed, the edge of the grout joint is neatly defined, and when the adjoining tile surface is very smooth, sometimes good results can be achieved. However, if the grout is not porous (from sealer or dirt), or the adjoining tile is rough or absorptive, it may be impossible to get a satisfactory result.
When grout has been stained to the point that it cannot be maintained or returned to its natural color, you can return the grout back to near its original color or any other color through the use of a “grout stain.” Some grout manufacturers make grout colors, others will recommend specific brands that they know work with their grout to correct color.
However, grout colorants work best with grout that has not been sealed. Grout that has been sealed or washed with oil-based soaps (Pine Sol, Murphy’s Oil, etc.) can be very difficult to color.
Grout stains are epoxy-based products that are specifically designed to penetrate into the grout and seal the surface with a permanent color. Once the grout has been stained, there is no need to seal it any further with a penetrating/impregnating sealer.
Prior to staining, the grout joint should be cleaned thoroughly to remove any dirt, oils, grease or sealers with a professional strength tile & grout cleaner. This can be purchased from most home improvement stores or through your local professional floor covering dealer.
The edge of the tile also makes a difference in the success of the colorant. Tiles with well-delineated edges are easier to treat than tiles with a large bevel or textured edge. When the colorant is applied, some will get on the tile. The easier it is to remove from the tile (and the better it sticks to the grout), determines in part how good the finished result appears.
Also, you will want to try a test area since grout treated with a colorant does not look the same as originally colored grout. On the plus side, grout colorants also seal the grout and protect it with an “epoxy-like” finish. Typically, grout that has been treated with a colorant does not need to be sealed.
Cementitious grout, as you may have observed, is porous. It can absorb a stain. Looked at under a microscope, there is a large surface area to absorb stains. For this reason, many owners choose to seal their grout. Typically, the better the sealer, the more the grout joint is protected. Even better, if epoxy grout is used, it is virtually as stain proof as the tile.
Removing stains from cementitious grout is similar to removing stains from clothing. The same cleaners you might use on clothes to get out a stain should also work on grout.
Keep in mind, however, that grout is based primarily of cement and sand. Sand, like glass, is unaffected chemically by most cleaners. Cement is not; rather, it is alkaline based and is dissolved by acids. As baking soda and vinegar react, so do grout and vinegar.
Accordingly, it is better to clean grout with an alkaline cleaner (Spic and Span, Mr. Clean, etc.) than an acid-based cleaner. There are also specialty cleaners available at most tile retailers that are designed for tile and grout. There are also cleaners with enzymes that attack stains similar to enzyme pre-soaks for laundry.
The same cleaner that works on the grout generally will work well on the tile. In fact, the tile is usually so easy to clean, it can often be cleaned with water.
Just a few more important points: As the grout can absorb the soap as well as a stain, do not clean with oil- or wax-based cleaners (Murphy’s Oil Soap, Pine Sol, etc.). These products will leave a waxy or oily film in the grout. Even good alkaline cleaners, if not properly rinsed, will leave a sticky soap film. This usually attracts dirt. In fact, truly clean ceramic tile without any sticky soap film will stay very clean as tile does not tend to hold an electrostatic charge, which can attract some kinds of dirt.
The absolutely best way to clean grout is to apply the cleaner and then vacuum (“shop vac”) up the dirty water. This lifts the dirt off the joint. Apply rinse water and vacuum that water up. This lifts off any remaining soap film.
There are tile installers that remove very stubborn stains on grout with an acid (such as straight vinegar or a stronger acid). There they have elected to dissolve the top layer of grout molecules so the stain is no longer attached to anything. While this works, it is not recommended by the grout manufacturers. The grout usually n eeds to be regrouted afters. Also, extreme care should be used when handling any acids.
Should you be unable to get your grout clean through conventional methods, you may also want to try steam. Some stains that do not respond to conventional cleaners will come clean when subjected to pressurized steam.
As a last resort, some installers elect to cut out the grout and regrout. This is possible, although care must be taken to not damage or loosen the tile. Generally it is not possible to grout directly over the old grout without cutting the old grout out. The same contaminants that made the old grout dirty may prevent new grout from sticking properly.
To prevent staining in the future, you should seal the grout.
Generally, sealer is a very good idea for cementitious grout (regular grout – not epoxy grout). For glazed floor tile, it is not a good idea to spray anything on the tile. The glaze of the tile will be easier to clean and longer lasting than any coating. For unglazed tile, sealers are generally recommended, although it is important to follow the recommendations of the tile manufacturer.
For cementitious grout, there are two broad classes of sealer: penetrating sealer that chemically bonds with the grout and repels water (and water based stains) and topical sealers that coat the surface of the grout and repel almost everything (until they are worn off by foot traffic).
Each type of sealer has its advantages and disadvantages. Additionally, there are hybrids on the market combining advantages.
In general, topical sealers are less expensive but give the grout a plastic appearance. Also, they are subject to wear and tear and are very sensitive to water in the grout while curing. As stated above, the plastic coating does block almost everything until it is compromised by foot traffic.
Penetrating sealers are more expensive but also more durable. There are also penetrating sealers that repel oil-based stains that are even more expensive. They can be applied on the grout sooner than the topical sealers, as they are usually vapor permeable. Since they do not coat the grout (but penetrate in), they do not change the large microscopic surface area. While stains don’t penetrate, they can be a little harder to remove (just a little) because the sanded texture of the grout hasn’t been changed.