How to Clean Mold in Shower Grout Naturally

Mold in shower grout is a common problem. High humidity combined with porous grout is a perfect habitat for mold. The lack of ventilation, shower screens, or curtains make this situation even worst, creating a haven for black mold. This was a problem in our bathroom. Here is how I have cleaned mold in shower grout naturally, without bleach, borax, WC cleaners, or any toxic substances.

 

2 step method

Two steps are required to get rid of the mold for good.

Step 1: Remove the mold
Step 2: Eliminate the mold triggers

 

Step 1: How to remove mold from grout naturally

Many sources advise using baking soda and vinegar as a natural agent to remove mold from the shower grout. I have decided to test this advice out, and the results were unexpected.

 

Optimum pH

The primary reason why baking soda and vinegar works well in combating mold lies in their pH. The mold usually grows in pH 3 – 7 (depending on the type of mold). If you have black mold in shower grout, the chances are that you are dealing with the Stachybotrys Chartarum. Its optimal pH for growth is 5.6-6.0 (source). Because of that, to get rid of the mold and keep it away, it helps to use ingredients that change the pH of the infested area, creating a hostile environment for the mold.

Ingredient	App. pH
Vinegar	2.0-3.0
Baking Soda	8.3
Water	7.0
3 % Hydrogen Peroxide	6.0

 

I know that using baking soda and vinegar is a widely spread tip; however, I have seen various alternatives of how to use those ingredients, e.g.:

– Baking Soda + Water
– Baking Soda + 3% Hydrogen Peroxide
– Baking Soda + White Vinegar
– Baking Soda + White Vinegar + 3% Hydrogen Peroxide
– Vinegar

But what is the best option? I have tested all the combinations mentioned above, leaving them to sit in the grout for about 20-30 minutes. First, I have started with 30 minutes, but then I have shortened it to 20 minutes, and the results seemed similar. The findings were quite surprising.

 

What is the best natural way to get rid of mold in shower grout

Vinegar

Vinegar is often suggested to be used in household cleaning. However, when it comes to grout, it seems that we should be careful. According to multiple sources, vinegar should not be used as a grout cleaner. The reason is that grout usually consists of sand and cement. The cement is highly alkaline and dissolves in acid (source). By using vinegar (probably a lot of it and for an extended period of time), you might damage the grout. Even though I have come across “industrial strength” grout cleaners that are highly acid (pH<1), since I am not a professional grout cleaner nor deal with extremely stubborn stains, I choose to stay away from cleaning grout with the acidic solutions, like vinegar.

Also, vinegar shouldn’t be used on, e.g., natural stone, so if you choose to use it, make sure that your tiles are suitable for acid cleaning agents.

Before I have come across the information stated above, I have tested vinegar on mold. It was my least favorite variant. Even though it worked, it was harder to scrub off the mold, and a small residue stayed in the grout. However, this could have happened because the area was more infested, and it just needed another round of vinegar or more scrubbing.

 

Baking soda mixes

The tested baking soda mixes were:
– Baking Soda + Water
– Baking Soda + 3% Hydrogen Peroxide
– Baking Soda + White Vinegar
– Baking Soda + White Vinegar + 3% Hydrogen Peroxide

The baking soda mixes made it easier to get rid of the visible mold compared to the vinegar. The mold came off relatively easy thanks to the abrasive properties of baking soda. I have tried all four combinations of soda mixes, and by judging the surface area, I found the results to be quite similar. Unfortunately, I can’t evaluate how well each mix worked inside the porous grout. Compared to the vinegar, the process of applying the solution was slower. However, the significant benefit was the fact that you don’t work in the choking odor of vinegar. But which mix was the best? When researching this topic, I have realized that some of the combinations seem wrong in principle.

 

Can you mix baking soda and vinegar to kill mold?

Mixing vinegar and baking soda to kill mold seems wrong in principle. By combining vinegar and baking soda, you get a solution with Sodium Acetate (source), which is a type of salt. The final mix is less alkaline or acidic than the primary ingredients (source). Since the working agent in vinegar and baking soda (source) is their pH, this effect is not desirable. The goal is to stay as far as possible from the optimal pH for mold growth, which is pH 3 – 7. For this reason, to get rid of mold, It is preferable to use a mix of baking soda and water (or 3 % hydrogen peroxide), which does not neutralize a high alkaline pH of the baking soda.

 

The best natural cleaning mixture

In my opinion, the best natural cleaning mixture for black mold in the grout is a thick paste created from baking soda and water (or 3% hydrogen peroxide).

 

How to get rid of mold in the grout with baking soda

When using a mix of baking soda (Amazon link) and water to eliminate mold, there is one thing to remember. Use such a ratio so that it creates a thick paste. Thanks to that, the mixture will stick to the grout in the place where you need it and won’t slide down. This way, all ingredients can penetrate the infested area and do their job. I don’t have the exact ratios of the mix; however, I found it fairly easy to make just eyeballing it :). Just put as much baking soda as you need to a bowl and gradually add some water. Keep mixing while you are pouring the water in, making sure that the paste is still thick enough. If you accidentally add too much liquid, use a tissue and drain some of the moisture. It works great.

Then, use a brush (I like to use an old toothbrush) to apply your paste on the grout and leave if for about 20 minutes. After that, scrub the grout with the toothbrush. The abrasive soda will help you to get rid of the mold. When cleaning the mold, wearing protective clothing, like rubber gloves, a respirator, and goggles, is recommended.

After cleaning the mold, you might end up with tiny traces of mold here and there. This might be due to the uneven distribution of the paste or because some places were more infested than others, and need longer treatment. Try to repeat the whole process in those spots.

 

Step 2: Eliminate the mold triggers

Removing the mold is just half of the job done. If you will not change the environment in the shower, it is a matter of time until the mold will form again. For this reason, it is essential to detect what was the cause of mold growth and try to limit it.

Here are the two essential factors that might be the cause of the mold in your shower: humidity and pH.

 

Humidity

If you have mold in your shower, you are probably dealing with a hydrophilic mold type such as Stachybotrys (black mold, source), which needs high water activity to grow. Because of that, it is essential to limit the moisture to a minimum. Here are a couple of tips, how to achieve it:

1. Install a bathroom exhaust fan above the shower. It should help to remove the humidity from the bathroom.
2. Take cooler showers to limit the steam. It is a money-saving and healthy option.
3. Use a squeegee to remove water from the walls after you take a shower. It will help the walls to dry quicker, which should hinder the mold’s growth. As a bonus, you will decrease the amount of soap scum that might build up on the walls or shower doors.

 

pH

As it was stated earlier, mold thrives in pH 3 – 7. Changing the pH of the grout will help you to create a hostile environment for the mold. For this purpose, from time to time, pour a solution of baking soda and water (I have chosen a ration of 50:50 since it has pH around 8) onto the shower walls where the mold used to form. This way, you will protect the grout from the potential future mold build-up.