---
title: "How to remove mould from silicone sealant in a bathroom"
description: "How to clean black spots in silicone around a bath, shower or sink, how to use chlorine or peroxide safely, and when it is better to replace the sealant."
url: https://uklid123.cz/en/blog/plisen-v-silikonu-koupelna
language: en
updated: 2026-11-06
publisher: Úklid 1-2-3 (info@uklid123.cz, +420 608 486 486)
---

Kitchen and bathroom

# Mould in silicone sealant: when to clean it and when to replace it

Black spots in the silicone around your bath or shower: how to clean them, how to work safely with chlorine, and how to tell when it is time to cut out the sealant and apply new.

Úklid 1-2-3 editorial team · Published 6 November 2026 · Last reviewed 6 November 2026 · 8 min read

## In short

- Surface mould in silicone can usually be removed with washing-up liquid and an anti-mould product used according to its label.
- If the spots do not change after repeated cleaning, or the silicone is cracking and peeling away, it is more sensible to replace it.
- Never mix chlorine-based products with acidic cleaners or ammonia; ventilate and wear gloves.
- Apply new silicone only to a clean, dry surface and do not seal mould in underneath it.
- The best way to stop mould returning is to dry the joint after showering and ventilate the bathroom.

Black spots in the silicone around a bath, shower or sink are mould that has taken hold on sealant that is constantly damp. If they are only on the surface, it is usually enough to wash the joint with washing-up liquid, treat it with an anti-mould product exactly according to its label, then rinse and dry it. If the spots do not disappear even after repeated cleaning, or the silicone is cracking and peeling away from the surface, it is more sensible to cut it out and apply new sealant.

## Why mould appears in silicone

The silicone joint around a bath or in a shower enclosure is wet for most of the day. Water collects in the corners, soap and shampoo residue settles on it, and the bathroom often goes unventilated. These are conditions in which mould thrives.

The US Environmental Protection Agency sums this up simply in its [guide to mould and moisture](https://www.epa.gov/mold/brief-guide-mold-moisture-and-your-home) : the key to controlling mould is controlling moisture, and if you do not solve the water problem, the mould will come back. Cleaning alone therefore helps only for a while unless you change how long the joint stays wet.

The most common causes:

- the bathroom is not ventilated after showering, or the fan runs only briefly,
- water stands on the joint because it is not wiped off after showering,
- soap deposits remain on the silicone,
- bottles and cups permanently stand on the joint, so it never dries underneath them,
- the silicone is old, cracked or peeling, and water seeps in behind it.

This article deals only with silicone joints. If there is mould on the plaster as well, follow the article [Mould on walls: how to remove it safely and why it comes back](https://uklid123.cz/blog/plisen-na-zdi-jak-odstranit) . Cement grout between tiles is covered in the guide [how to clean grout in the bathroom](https://uklid123.cz/blog/jak-vycistit-spary-v-koupelne) .

## Clean it or replace it straight away?

Before you begin, look closely at the joint and try pressing it lightly with your finger. Decide based on what you see:

| Condition of the silicone | What to do |
| --- | --- |
| Individual black spots or a grey film, the silicone is flexible and holding | Clean it following the procedure below |
| The spots lightened after the first cleaning but did not disappear | Repeat the cleaning once or twice |
| The spots do not change even after repeated treatment | Replace the silicone |
| The silicone is hard, cracked, peeling, or there is water standing behind it | Replace the silicone and find out where the water is getting in |
| Mould is also on the surrounding wall or covers a large area | Find and remove the source of moisture; for extensive infestation, consider a specialist |

To give you an idea of scale: the EPA states that an area smaller than roughly 10 square feet (about 0.9 m²) can in most cases be handled by yourself. A silicone joint generally falls within that area, but mould on the surrounding walls may not.

## Equipment and products

- rubber gloves; for working with a chlorine product, the EPA recommends gloves made of natural rubber, neoprene, nitrile, polyurethane or PVC,
- protective goggles, because when spraying into corners a drop can easily splash into your eyes,
- ordinary washing-up liquid and warm water,
- a soft brush (an old toothbrush will do) and a sponge without an abrasive side,
- a microfibre cloth or paper towels for drying,
- an anti-mould product containing chlorine or hydrogen peroxide, intended for bathroom surfaces.

Do not use abrasive sponges, steel wool or scrapers for cleaning. Scratched silicone has a more uneven surface to which dirt and mould cling even better.

## Cleaning silicone step by step

- **Ventilate and protect yourself.** Open the window, switch on the fan, and put on gloves and goggles. Remove cosmetics and mats from the shower enclosure or bath.
- **Wash the joint with washing-up liquid.** Use warm water with washing-up liquid and a brush to remove soap deposits and loosened mould. The EPA recommends first scrubbing mould off hard surfaces with water and detergent.
- **Rinse and dry.** An anti-mould product works better on a clean surface, and detergent residue does not dilute it.
- **Test the product on a hidden spot.** Especially with coloured silicone and with delicate surrounding surfaces (stone, metal, varnished wood by a kitchen unit), check that it will not cause discolouration or damage.
- **Apply the anti-mould product.** Spray at close range directly onto the joint, not into the air. Follow the contact time and any dilution exactly according to the label.
- **Rinse thoroughly.** Rinse the joint and the surrounding tiles with clean water so that no product residue is left on them.
- **Dry and ventilate.** Wipe the joint dry and keep the bathroom ventilated until the smell of the product has gone.

If the spots have only lightened, you can repeat the procedure the next day. If nothing changes even after two or three treatments, cleaning will not improve the result any further and replacing the silicone is more suitable.

## Chlorine, peroxide or just washing-up liquid

For a light grey film, washing-up liquid and a brush are often enough. For black spots, anti-mould products are used, most often containing chlorine or hydrogen peroxide. Both types irritate the skin and eyes, so the same rules apply to both: read the label, ventilate and wear gloves.

If you were to dilute a chlorine solution yourself, the US [CDC states](https://www.cdc.gov/mold-health/about/index.html) that for removing mould from hard surfaces the solution should be no stronger than 1 cup of bleach per 1 gallon of water (approximately 240 ml per 3.8 litres). Ready-made anti-mould sprays are usually not diluted, so always follow the label of the specific product.

### Safety when working with chlorine

- **Never mix chlorine-based products with acids** (vinegar, citric acid, limescale removers, acidic toilet cleaners) **or with ammonia.** The CDC warns that mixing bleach with ammonia or other cleaners produces a toxic gas.
- If you also want to remove limescale in the same bathroom, do it at a different time and rinse the surfaces thoroughly with water in between.
- Ventilate during the work and afterwards.
- Use gloves and protective goggles.
- If you experience burning of the eyes, nose or throat, or difficulty breathing, go out into fresh air. The [CDC states](https://www.cdc.gov/chemical-emergencies/chemical-fact-sheets/chlorine.html) these symptoms for inhalation of chlorine and recommends leaving the building and breathing clean air as the first step. For questions about poisoning, you can contact the [Toxicology Information Centre](https://www.tis-cz.cz/) (224 91 92 93 or 224 91 54 02).

An overview of other risky combinations can be found in the article [Which cleaning products should never be mixed](https://uklid123.cz/blog/nebezpecne-kombinace-cisticich-prostredku) .

## When and how to replace silicone

Replacement makes sense when the stains cannot be cleaned, the silicone has lost its flexibility, or it is cracking or peeling. We describe the procedure in general terms; specific instructions can always be found in the technical data sheet of the sealant you use.

- **Cut out the old silicone.** Using a sharp knife or a plastic silicone scraper, cut it along both edges and pull it out. With an enamelled or acrylic bath, work carefully so as not to leave scratches.
- **Remove the residue.** The technical data sheet for Den Braven sanitary silicone states that the surface must be clean, firm and free of loose particles of dust, grease and oil.
- **Treat the mould under the sealant and let everything dry.** The EPA explicitly warns that mouldy surfaces should not be painted over or caulked; clean and dry them first.
- **Choose a suitable sealant.** Sanitary silicone is used in bathrooms and kitchens. For acrylic baths, the manufacturer Den Braven states on the [page of its acetate sanitary silicone](https://denbraven.cz/produkt/sanitarni-silikon/) that a neutral silicone must be used. According to the technical data sheet, acetate silicone is not suitable for, among others, marble, concrete and aluminium.
- **Apply and smooth the silicone.** According to the [technical data sheet](https://dokumentace.denbraven.cz/?p=05+Silikony%2FSanita%CC%81rni%CC%81+silikon%2FTechnicky%CC%81+list&dl=TL+04_51+rev5+Sanit%C3%A1rn%C3%AD+silikon+RL.pdf) , this sealant is applied at a temperature of +5 to +40 °C and smoothed within 10 minutes of application.
- **Let the silicone cure.** For the product mentioned, a surface skin forms in about 13 minutes and the sealant cures to a depth of 2 mm in 24 hours (at 23 °C and 55% humidity). A thicker joint needs more time, so use the shower or bath only after the time stated by the manufacturer of your sealant has passed.

According to the technical data sheet, sanitary silicone cannot be painted over. There is therefore no point in painting a greyed joint; it can only be cleaned or replaced.

## How to stop mould coming back

- After showering, squeegee the water off the walls and glass and wipe the joint dry.
- After bathing, ventilate the bathroom or leave the fan running until the steam has gone.
- Do not put bottles and cups directly on the silicone joint.
- Once a week, wash the joint with washing-up liquid so that soap deposits do not build up on it.
- If water seeps behind the silicone, or the bath flexes under weight and the joint tears, deal with the cause, otherwise the problem will keep recurring.

Regular cleaning of glass and the shower tray is described in the article [How to clean a shower enclosure and keep the glass clean](https://uklid123.cz/blog/jak-vycistit-sprchovy-kout) . Thorough cleaning of the bathroom, including the joints, is a standard part of [deep cleaning](https://uklid123.cz/sluzby/generalni-uklid) ; if you are considering ordering it, you can find indicative prices in the [price list](https://uklid123.cz/cenik) .

## Frequently asked questions

### Can mould be removed from silicone completely?

If the stains are only on the surface, usually yes: washing with washing-up liquid, treating with an anti-mould product according to its label, then rinsing and drying will help. If the spots do not disappear even after two or three treatments, or the silicone is cracking and peeling off, cleaning will not improve the result. In that case it is more sensible to cut out the old silicone, clean and dry the surface, and apply new sanitary silicone.

### Can I use Savo or another chlorine-based product on mould in silicone?

Yes, chlorine-based products are used against mould on hard surfaces. Follow the dilution and contact time on the label, test the product on a hidden spot, ventilate, and wear gloves and goggles. Never mix them with vinegar, limescale removers, acidic toilet cleaners or ammonia. After the product has worked, rinse the joint thoroughly with water and dry it.

### Why does mould return to silicone after cleaning?

Mould needs moisture. If the joint stays wet after showering, the bathroom is not ventilated, or water seeps in behind damaged silicone, mould will sooner or later appear again. It helps to squeegee off the water, wipe the joint dry, ventilate, and wash the joint with washing-up liquid once a week. Old, cracked silicone is better replaced.

### How long after replacing silicone must I wait before using the shower?

It depends on the specific sealant and the thickness of the joint, so follow the manufacturer's technical data sheet. For example, for Den Braven sanitary silicone a surface skin forms in about 13 minutes and the sealant cures to a depth of 2 mm in 24 hours at 23 °C and 55% humidity. A thicker joint or a cooler bathroom means a longer wait.

### What silicone should I use for an acrylic bath?

For its acetate sanitary silicone, Den Braven states that a neutral sanitary silicone must be used for acrylic baths. In general, you can check whether a sealant is suitable for the material of your bath, tiles or worktop in the technical data sheet or on the product packaging. According to the manufacturer, acetate silicone is not suitable for, for example, marble, concrete or aluminium.

## Sources

- [A Brief Guide to Mold, Moisture and Your Home – U.S. Environmental Protection Agency](https://www.epa.gov/mold/brief-guide-mold-moisture-and-your-home) (checked 6 November 2026)
- [Mold – Centers for Disease Control and Prevention](https://www.cdc.gov/mold-health/about/index.html) (checked 6 November 2026)
- [Chlorine | Chemical Emergencies – Centers for Disease Control and Prevention](https://www.cdc.gov/chemical-emergencies/chemical-fact-sheets/chlorine.html) (checked 6 November 2026)
- [Technický list TL 04.51 Sanitární silikon – Den Braven](https://dokumentace.denbraven.cz/?p=05+Silikony%2FSanita%CC%81rni%CC%81+silikon%2FTechnicky%CC%81+list&dl=TL+04_51+rev5+Sanit%C3%A1rn%C3%AD+silikon+RL.pdf) (checked 6 November 2026)
- [Sanitární silikon – Den Braven](https://denbraven.cz/produkt/sanitarni-silikon/) (checked 6 November 2026)
- [Toxikologické informační středisko – úvodní stránka](https://www.tis-cz.cz/) (checked 6 November 2026)

Prepared by the Úklid 1-2-3 editorial team with the help of AI and verified against the sources listed. Manufacturers' instructions and regulations change: always follow the current wording of the source and the product label. This article is general information, not professional or legal advice. This article was translated from Czech with the help of AI. The sources are in the original language.

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