What is that green and black stuff that grows on pool decks? Read this article to learn what it is, how to remove it, and how to minimize the likelihood of future discoloration.

Surface Care PROS Support April 25, 2021

Are you considering natural stone as a material for your kitchen or bath new construction or renovation plans? You’ll need to enlist the services of both a stone fabricator and a stone restoration contractor. Here are the details.

Surface Care PROS Support March 25, 2021

If your grout looks dirty or seems to be a dirt magnet, there are real, lasting solutions available. Read this article to learn how to resolve dirty grout problems once and for all.

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Surface Care PROS Support January 28, 2021

For anyone considering having limestone installed, as well as anyone with an existing installation, read this article to learn where limestone works best, why limestone is not suitable for wet areas, and how to care for limestone.

Surface Care PROS Support December 2, 2020

Urine stains and odors can be difficult to remove from natural stone. Here are some step-by-step instructions for both urine stain and odor removal.

Surface Care PROS Support October 27, 2020

We have received many calls regarding “staining,” and in some cases the issue is not a stain at all. Here are some examples of stone problems that look like stains but are not actually stains.

Surface Care PROS Support September 30, 2020

Quartzite will not etch or scratch. If you have quartzite that is etched and scratched, it may actually be marble. This article explains the difference so that you can tell what countertop material you truly have.

Surface Care PROS Support August 27, 2020

Home and business owners and property managers have a common complaint about the grout in their showers and floors turning yellow. Testing can help determine what is causing the problem. Solutions will vary, depending on the cause. Here are the details.

1. Toiletries

Shampoos, soaps, and other personal items used in showers contain chemicals that can cause discoloration, and hence, yellowing of grout. This is especially true of hair dyes and shampoos that contain coloring agents. Check the product labels to see whether products contain dyes, polymers, or other ingredients that may cause grout to turn yellow.

2. Body Oils

Skin and hair oils contain many contaminants that can cause discoloration of not only grout but also tile. These body oils are what cause the familiar yellow stain, ring-around-the-collar.

3. Sealers and Waxes

Sealers and various waxes can contain polymers that can discolor over time and cause yellowing.

4. Grout Type

Numerous grout types are prone to yellowing. For example, white epoxy grouts are notorious for turning yellow.

5. Cleaning Products

Certain cleaners, especially those that contain dyes, can cause discoloration of grout. Household bleach commonly discolors grout. Check the product labels to see whether products contain dyes, polymers, or other ingredients that may cause grout to turn yellow.

6. Iron

Certain water supplies contain iron. Water containing iron can deposit minerals on the grout that can oxidize and cause a yellow discoloration. If the water used to mix the grout during installation contained iron, this can also cause discoloration. Your professional stone and tile restoration technician can do a test to determine if your water supply and/or your grout contain iron. If your water supply contains iron, install a water filtration system.

7. Dirty Water

Water used to mop floors can rapidly get dirty. The dirt, oils, etc. will settle on the grout lines and cause a yellow cast. It is important to keep your mop head clean and change the mop water often.

8. Cigarette Smoke

Cigarette smoke can settle on grout lines, causing the grout to turn yellow. Obviously, smoking outdoors will eliminate further yellowing of grout, as well as walls, furniture, and household items.

9. Aerosol Sprays

Hairspray, air freshener, and other aerosol sprays can sometimes cause grout discoloration. Check the product labels to see whether products contain dyes, polymers, or other ingredients that may cause grout to turn yellow.

10. Bleed Over

Certain tile types, such as white marble, contain iron. Iron from the tile can bleed into the grout and oxidize, causing the grout to turn yellow.

As you can see, there are numerous reasons for your grout to turn yellow. An experienced stone and tile restoration professional will have the knowledge, skills, and equipment to accurately diagnose and resolve most grout yellowing problems.

Recolor or Replace Yellowed Grout?

A good professional cleaning can often remove contaminants that cause grout to turn yellow. Once your grout is completely clean, ask your professional stone and tile restoration technician to seal the grout with a good penetrating sealer. Be sure to take the necessary precautions, such as discontinuing the use of certain products, smoking outside, or installing a water filtration system, so that your grout will not turn yellow again.

Some grout stains will permanently set, especially those that have been on or in the grout for a long time. If so, your stone and tile restoration technician can apply a high-quality grout color sealer, for a fresh, clean look, as long as the grout is in good condition and not falling apart. Grout that is in poor condition should be removed and replaced.


This article, written by Fred Hueston, Chief Technical Director of SurpHaces, and president of Stone Forensics, is one of a series of articles written and published on behalf of Surface Care PRO Partners.

Removing graffiti on stone, tile, brick, or masonry? Put the pressure washer away. It can be problematic and/or ineffective. Read this article for guidance.