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What is causing my grout to have variations in color?
Uneven grout color is not normal, but there can be a number of things that can cause blotchy grout. Also, how uneven the color appears can be somewhat subjective. Certain color grouts are not as easy to control. The easiest colors to work with are the medium grays and beiges as opposed to bright colors, whites, blacks, etc. Since most grout is cement based, it tends to turn gray with time and cleaning. Grout sealers are now recommended to reduce this effect.
Some of the things that can cause color variation include:
- Too much water added in mixing the grout.
- Improper cleaning of the grout and grout haze off the tile (usually by wiping too soon and with too much water).
- Leaving plastic spacers in the joints.
- Having the thinset adhesive fill part of the joint and showing through.
- Improper mixing of the grout by using an improper amount of water.
- Mixing partial bags (this is a problem if the colorant is not evenly distributed).
- Using grout from a bag that was previously opened (and gained moisture during storage).
- Adding water after the first mixing (rehydrating).
- Failure to slake the grout.
- Improper joint packing.
- Inadequate cleaning of the sponges.
- Using unclean water.
- Defective grout itself (this happens once in a while).
- Dirty tools or shoes that stain the grout (we have actually had that happen to us, where workers racked in clay on their shoes).
- Foot or other traffic too soon over the joints. Curing time is on the bag but can be up to three days for some grout.
Sometimes the tile itself can have a microporoisty (small pores in the tile body, especially with porcelain tile) condition that sucks the moisture out of the grout too fast or in an irregular pattern. In many cases it is hard to tell exactly what went wrong by looking at the tilework. I would suggest that you ask the tile installer what he or she thinks about the workmanship and techniques used. One can always remove the grout and replace it if that is the only acceptable solution.
If you have some of the grout left, the TCNA lab can test the grout.
Our subsidiary consulting company, TCA-Team, is available for site consultations and failure analysis on a fee basis, should you desire an investigation.
Is there a standard that addresses color variations in grout?
There are no ANSI standards that address color variations in grout.
This is in part because some colors are more prone to uneven color than others due to the dyes used. Also, depending on the tile, it may be impossible to allow the grout to sufficiently cure for best color uniformity and still remove it from the tile. In other words, the grout must be removed before the color has a chance to set.
However, there are many installation mistakes that can cause uneven color including improper mixing of the grout (typically by using too much water), mixing partial bags (this is a problem if the colorant was not evenly distributed), using grout from a bag that was previously opened (and gained moisture during storage), adding water after the first mixing (rehydrating), failure to slake the grout, improper joint packing, using too much water too soon when wiping the joints, inadequate cleaning of the sponges, using unclean water, allowing traffic on the floor too soon, etc.
Where absolute color uniformity is desired, epoxy grouts are often recommended (they are much more expensive though) as they cure and clean up differently from cementitious grout.
Unfortunately, with regular cementitious grout, there is little that can be done once the grout is in place except for attempting to use a grout colorant. Grout colorants work best with grout that has not been sealed. Grout that has been sealed or has been washed with oil-based soaps (Pine Sol, Murphy’s Oil, etc.) can be very difficult (or impossible) to color.
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.
Grout treated with a colorant also has a different texture than originally colored grout. On the plus side, grout colorants usually seal the grout in addition to changing its color. Typically, grout that has been treated with a colorant does not need to be sealed.
Can I correct the color of my grout?
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 has been 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 Centers 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.
The color of the grout in my shower is inconsistent and in some areas the grout is a darker color?
Uneven grout color is not uncommon, although in this case, the darkening may be caused by water (more about that later).
This is in part because some colors are more prone to uneven color than others due to the dyes used. Also, depending on the tile, it may be impossible to allow the grout to sufficiently cure for best color uniformity and still remove it from the tile. In other words, the grout must be removed before the color has a chance to set.
However, there are many installation mistakes that can cause uneven color including improper mixing of the grout (typically by using too much water), mixing partial bags (this is a problem if the colorant was not evenly distributed), using grout from a bag that was previously opened (and gained moisture during storage), adding water after the first mixing (re-hydrating), failure to slake the grout, improper joint packing, using too much water too soon when wiping the joints, inadequate cleaning of the sponges, using unclean water, allowing traffic on the floor too soon, etc.
Where absolute color uniformity is desired, epoxy grouts are often recommended (they are much more expensive though) as they cure and clean up differently from cementitious grout.
Can I paint over grout?
Changing grout color is more commonly done but; again, the results are generally not as good as the original item. The color in grout, unlike tile, comes from liquid dispersed pigments. Obviously, these are not fired but rather become part of the cement/sand matrix. Grout is usually colored with an epoxy paint made for the purpose and sold in tile shops. When the grout is new, has not been sealed, and 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.