How Bicarbonate of Soda Removes Bathroom Mould from Sealant

The answer may, unexpectedly, already be sitting in your kitchen cupboard.

In homes throughout the UK, the US and elsewhere, black mould staining on bathroom sealant is a common source of irritation. Regular cleaning, pungent sprays and aching shoulders can appear to achieve very little. However, cleaning specialists say one everyday cupboard ingredient can remove these marks quickly, without expensive products or hiring professional help.

Why bathroom joints attract mould

Even bathrooms that look spotless can offer the perfect environment for mould. Heat, moisture and inadequate airflow provide microscopic fungi with the conditions they need to develop.

Joints of sealant surrounding showers, baths and basins are especially exposed. Water collects in their narrow channels, while soap deposits and shampoo residue provide a food source. Eventually, black or brown marks begin appearing on silicone or grout.

Mould on bathroom joints is not just a cosmetic problem. Spores can affect air quality and irritate sensitive airways.

Health bodies regularly associate ongoing mould exposure with respiratory irritation, particularly for those with asthma, allergies or compromised immune systems. Older people and children may also be at greater risk.

For that reason, the seemingly insignificant dark lines on bathroom sealant need more attention than a brief wipe with a sponge.

Why standard cleaning products can fall short

Bleach sprays and heavily scented detergents are often the first choice in many households. Although they may initially fade the visible marks, the darker staining commonly returns within a few weeks.

This repeating problem has three main causes:

• Bleach usually lightens the outer surface, but may not reach mould embedded further inside porous grout.
• Strong chemical products can gradually harm sealant, producing tiny cracks that give mould new places to settle.
• Poor ventilation is not addressed, meaning the humid environment continues to support fresh growth.

Cleaning professionals are increasingly recommending gentler, focused options that physically lift mould rather than simply concealing it.

Bicarbonate of soda: the cupboard ingredient for bathroom mould

A cheap, widely available product is being recommended by more home-care specialists: bicarbonate of soda, also known as baking soda. It is useful for far more than baking and deodorising fridges; it can also be an effective bathroom cleaner.

Its usefulness comes from several qualities:

• Its gentle abrasiveness helps to lift grime and biofilm without scratching tiles or most sealants.
• It has antifungal properties that interfere with mould growth.
• It neutralises unpleasant smells held in damp joints.
• It breaks down into harmless materials, making it an environmentally friendly option compared with harsh chemical cleaners.

Bicarbonate of soda can clean deeply, tackle odours and protect surfaces, all for a fraction of the cost of specialist sprays.

It is sold in the baking section of most supermarkets, where a small packet will generally cost less than a branded bathroom cleaner.

Making a bicarbonate paste to tackle mould

The approach becoming popular online and with cleaning professionals is intentionally straightforward. Rather than drenching the affected section, the idea is to make a dense paste that adheres to the bathroom joints.

Step-by-step recipe

For an ordinary shower cubicle or the edge of a bath, gather the following:

• Around three tablespoons of bicarbonate of soda
• A small amount of cold or lukewarm water
• An old toothbrush or compact scrubbing brush
• A sponge and a clean, dry cloth

Put the bicarbonate of soda into a small bowl and gradually add water, one teaspoon at a time. Mix until it forms a thick paste with a consistency more like toothpaste than runny cake mixture. If the paste slides off the spoon, too much water has been used, so add a little more powder.

Applying the paste to bathroom joints

When the paste is prepared, use it as follows:

1. Slightly moisten the mouldy joints to make the paste easier to spread.
2. With the toothbrush, work the paste directly into the stained lines, applying a generous layer.
3. Allow it to remain for a minimum of 15 to 30 minutes, giving it time to take effect.

The waiting time allows bicarbonate to soften stubborn deposits and detach mould from the surface instead of just smearing it.

Where mould is particularly severe, some professionals advise leaving the paste in place for longer, up to one hour, provided it does not become completely hard and dry. Should it begin drying out, lightly mist it with water from a spray bottle to reactivate it.

Scrubbing and rinsing bathroom sealant properly

Once the paste has rested, scrubbing completes the cleaning process. This physical action removes the mould loosened by the bicarbonate paste.

Tackle the area in small sections:

• Scrub along the joints using firm, short toothbrush strokes.
• If the paste is too gritty to work with, add a small splash of water to the brush.
• When the stains begin to fade, wipe the entire area with a damp sponge.
• Rinse thoroughly with fresh water so that no residue remains.
• Finish by drying the joints with a clean cloth or an old towel.

Drying is a stage that is often missed, but it is important. Wet surfaces recreate exactly the conditions that enabled mould to develop in the first place.

Stopping mould from returning

A single cleaning session can help, but preventive habits have the greatest impact. Specialists identify controlling humidity as the key factor.

The less time water spends sitting on your sealant, the less chance microscopic fungi have to settle and grow.

A few simple routines can make a substantial difference to bathroom conditions:

• Open the window or keep the extractor fan running for at least 15 minutes after every bath or shower.
• Wipe water from tiles, glass and joints with a squeegee or an old towel.
• Keep the shower door or curtain slightly open to improve air circulation.

Many cleaning advisers also recommend quickly wiping the joints every week with white vinegar. Its acidity makes the surface less hospitable to mould, particularly with repeated use. Apply the vinegar using a cloth or spray bottle, leave it for several minutes, then rinse and dry the area.

When a home remedy may not be enough

For most households, bicarbonate paste combined with improved ventilation produces noticeable results. In some cases, though, the mould issue may be more deeply rooted.

A musty odour that persists, or dark patches spreading over ceilings and walls, suggests a wider damp problem rather than merely unclean bathroom joints.

What “mould” on bathroom joints actually is

The black lines commonly described as “mould” are generally colonies of microscopic fungi. Spores remain in household air even when they cannot be seen, waiting for surfaces that are damp and moderately warm.

Grout and silicone around showers are particularly at risk. Silicone itself is not organic, but a fine layer of dirt, soap scum and skin oils can build up over it. Fungi feed on this coating before anchoring themselves in minute flaws in the surface.

This is why markings can appear in a brand-new bathroom after only a year when ventilation is inadequate. The issue is not so much about poor cleanliness as continuing moisture over time.

Real-life examples of small changes

Consider two otherwise similar homes, each with a bathroom of the same size and an identical type of shower. In the first, the extractor fan is not switched on and the door is closed straight after a hot shower. Droplets remain on the tiles for the entire evening. After a few months, pale grey lines start emerging along the joints.

In the second, a person takes 30 seconds after every shower to dry the joints with a towel and leaves the extractor fan running. They use bicarbonate paste once each month on any marks that look suspicious. One year later, the sealant remains much nearer to its original colour, and there has been no need to purchase specialist mould sprays.

The difference demonstrates that consistent, easy routines can alter the long-term result more effectively than relying on aggressive chemicals.

Risks, benefits and safe combinations of cleaning methods

Bicarbonate of soda is widely regarded as safe for household cleaning, though it still requires a few precautions. Its abrasive particles may leave marks on very soft materials, including high-gloss plastic, if used with excessive force. Test it first in a discreet small area.

Cleaning products should also be combined carefully. It can be tempting to mix vinegar, bleach and bicarbonate into a supposed super-cleaner, but doing so can be hazardous. Combining bleach with acids such as vinegar can produce chlorine gas. It is safer to use one approach at a time and rinse between methods.

Using gentle products in the right order often beats throwing a cocktail of chemicals at the same patch of mould.

Using bicarbonate and vinegar has financial as well as environmental advantages. Households may use fewer plastic bottles and reduce the amount of harsh residue entering the drain. Meanwhile, dry and clean bathroom joints can improve air quality and make everyday bathroom routines more comfortable.

For busy families, the benefit is straightforward: fewer dark marks, fewer harsh smells, and a fresher bathroom maintained with items already at home.