How to Get Rid of Mould on Curtains — What Actually Works (and What Makes It Worse)

In Australia’s coastal cities — Sydney, Melbourne, Brisbane, Perth — high humidity and poor window ventilation create the perfect conditions for mould growth on curtains. We see it constantly: homeowners who have scrubbed their curtains with bleach, only to watch the mould return within weeks. Or worse, they have ruined an expensive set of linen drapes trying to remove it.

This guide explains the mechanics of why mould grows on curtains and gives you a clear process for removing it based on your specific fabric type. No guesswork. No vague advice. Just what works.

Why Do Curtains Get Mould So Easily?

This is the question most cleaning guides skip over — and it is the reason so many people treat the symptom rather than the cause.

Curtains hang directly against or near windows, which are the single coldest surface in most rooms. When warm, humid indoor air hits that cold glass, it condenses. That moisture transfers to whatever is in contact with the window — usually the bottom hem and back of your curtains.

According to environmental health research, mould begins colonising fabric when relative humidity stays above 70% for more than 24–48 hours. In cities like Sydney and Melbourne, this threshold is regularly crossed during winter months, particularly in bedrooms and bathrooms where condensation is heaviest.

• 70%Humidity threshold for mould growth to begin on fabric
• 24–48hrsTime for mould to colonise damp fabric if not dried
• 1 in 3Australian homes have some level of mould issue

The three real causes of curtain mould in Australian homes are:

• Condensation from single-glazed windows — extremely common in older Australian homes, where the temperature gap between the glass and the room creates persistent moisture on curtain fabric
• Poor airflow behind hanging curtains — curtains that sit flush against the wall or window frame trap a pocket of stagnant, humid air with no way to circulate or dry out
• Delayed drying after washing — putting curtains back up before they are completely dry is one of the fastest ways to seed a mould problem that keeps coming back

Does Curtain Mould Actually Affect Your Health?

The short answer: yes — particularly for children, the elderly, and anyone with asthma or allergies.

Mould reproduces by releasing microscopic spores into the air. When your curtains have an active mould colony, opening or closing them agitates the fabric and sends a cloud of spores directly into your breathing zone.

How to Tell If It Is Mould — Not Just a Stain or Dirt

Before you reach for the cleaning supplies, make sure you are actually dealing with mould. Here is how to check:

• Colour and texture: Mould typically appears as fuzzy or powdery patches — black, dark green, grey, or sometimes pink. A regular stain is flat and does not have that surface texture.
• Location pattern: Mould almost always starts at the bottom hem (closest to the window sill where moisture collects) or where the fabric bunches against the rod at the top. Random stains appear anywhere.
• The sniff test: Mould has a distinctive musty, earthy smell. If your curtains smell damp even when they are dry, that is a red flag.
• The damp cloth test: Wipe a small hidden area with a white damp cloth. If it picks up a greenish or dark residue along with the odour, it is likely mould rather than a standard stain.
• The bleach spot test: Apply one drop of diluted household bleach to a tiny hidden area. If the discolouration fades within a minute or two, it is mould. Dirt and most stains will not react this way.

How to Remove Mould from Curtains Yourself — Step by Step

This process works for most standard fabric curtains (cotton, polyester, and linen blends). Always check the care label before you start, and do a small patch test with any cleaning solution first.

For curtains that cannot be washed (velvet, some linens, or heavily lined drapes), see our guide on how to remove mould from curtains without washing.

Which Cleaning Solution Should You Use on Your Fabric Type?

The biggest mistake people make is reaching for bleach on any curtain with mould. Bleach is corrosive and will destroy coloured, natural, and delicate fabrics. Here is what to use based on your curtain material.

Quick Reference: Which Method for Which Fabric?

Dealing with Stubborn Mould Stains That Will Not Budge

So you have cleaned the curtain and killed the mould — but there is still a shadow where it was. This is a common frustration. What has happened is that some mould species produce pigments that penetrate into the fabric fibres themselves. You have killed the mould, but the pigment remains as a physical change to the fabric.

Here is what you can try for stubborn residual staining:

• Lemon juice + sunlight: Dampen the stained area with lemon juice and hang the curtain in direct sunlight for 1–2 hours, then rinse. The citric acid combined with UV has a natural bleaching effect that is very fabric-safe — particularly effective on cotton and linen.
• Enzyme-based laundry pre-soaker: Products like Vanish Oxi Action contain enzymes that break down organic stains (mould is organic). Apply to the wet fabric, leave for 30 minutes, then wash as normal. Do not use on silk or wool.
• Hydrogen peroxide (3% solution): Available at chemists, hydrogen peroxide is a gentler bleaching agent than chlorine bleach. Apply to the stain, leave for 10 minutes, then rinse thoroughly. Do a patch test first on a hidden seam.
• Professional enzyme treatments: Significantly stronger than anything available at the supermarket and applied under controlled temperature conditions. If the steps above do not work, this is your next option.

For more detail on treating specific fabric types, see our guide on removing mould from fabric curtains, which covers treatment protocols for older, set-in stains. If you are wondering whether to clean the curtains while they are still hung up, spot cleaning curtains at home explains when that is practical and when it is not worth it.

When Should You Call a Professional? Here Is the Real Threshold

Many guides give vague advice like “call a professional for severe cases.” That does not actually help you decide. Here is the real breakdown from 5 years of doing this work:

You can confidently DIY if:

• The mould covers less than a 20cm × 20cm area and is caught early (still mostly surface-level)
• The curtains are standard cotton, linen, or polyester and are machine-washable
• There is no structural damage to the fabric — no weakening, thinning, or holes
• It is your first mould occurrence — the curtains have not been through multiple cleaning cycles already

You should call a professional if:

• The mould covers a large area (bigger than a dinner plate) or is present on both sides of the fabric
• Your curtains are velvet, silk, heavily lined thermal drapes, or carry a “dry clean only” label
• The curtains are valuable — custom-made, imported, or expensive — and you cannot afford to get it wrong
• The mould has returned after DIY cleaning more than once (this usually means the spores were never fully eliminated)

What does professional curtain mould removal actually involve?

Here is the real process — not the marketing version:

• Area preparation: Before work begins, the surrounding area is secured to prevent spores from spreading to other parts of your home during removal.
• Protective equipment: Appropriate protective gear is worn throughout the process, as working with active mould colonies requires proper precautions.
• Spore removal: Loose spores are carefully removed from both sides of the fabric before any wet treatment begins, using equipment designed to capture rather than scatter them.
• Fabric treatment: A fabric-safe solution is applied to the affected areas and left to break down the mould thoroughly before cleaning proceeds.
• Deep cleaning: Depending on the fabric type, curtains are cleaned using a method suited to the material — ensuring mould is eliminated from within the fibres, not just the surface.
• Controlled drying: Curtains are dried in a properly managed environment before being returned. Incomplete drying is the most common reason mould returns after cleaning.
• Final inspection: Once dry, curtains are inspected and, where appropriate, treated with a fabric-safe protective barrier to help resist future mould growth.

Find out more about our curtain mould removal service in Melbourne, or see how we handle it for Sydney customers. If you are comparing options, our breakdown of steam cleaning vs dry cleaning explains which method works better for mould specifically.

How to Stop Curtain Mould Coming Back

Treating mould once is frustrating. Treating the same curtains for the third time is expensive and demoralising. Here is how to break the cycle.

Tackle the root cause: window condensation

• Squeegee your windows each morning during winter — this removes condensation before it transfers to your curtains. It takes 30 seconds and makes a real difference in high-humidity rooms.
• Move curtains away from the glass by at least 5cm — give air room to circulate between the fabric and the window surface.
• Install a dehumidifier in rooms with persistent condensation. Set it to maintain humidity below 55%. Bedrooms are the most common problem area in Australian homes.
• Improve ventilation — open windows for 10–15 minutes each morning, even in winter. This exchanges the humid overnight air before it settles into the fabric.

After cleaning — keep it from returning

• Make sure curtains are completely dry before re-hanging — every seam, fold, and pleat.
• Spray cleaned curtains with a diluted tea tree oil solution (20 drops per 500ml of water) — tea tree has natural anti-fungal properties and is safe on most fabrics.
• Clean your curtains regularly — at least every 12 months for most homes, and every 6 months if you are in a humid climate. Read our guide on the importance of regular curtain cleaning for more on timing.

If you live in Queensland, Darwin, or coastal NSW where the humidity is genuinely relentless, our dedicated guide on maintaining curtains in humid climates to prevent mould is worth reading in full.

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Frequently Asked Questions

Ques. Can I just use bleach on my curtains to kill mould?

Ans. Bleach will kill mould, but it can also damage curtains unless they are white and made of cotton or a synthetic fabric. It removes colour and weakens natural fibres such as linen or silk. A safer option is white vinegar or a baking soda paste.

Ques. Does vinegar actually kill mould, or just clean the surface?

Ans. White vinegar is naturally anti-fungal and kills most mould species. However, it may not fully remove deeply embedded mould, so severe cases may still require professional treatment.

Ques. How often should I clean my curtains to prevent mould?

Ans. Once a year is enough for most homes. In humid areas, cleaning every 6 months is recommended. Always treat mould early to avoid deeper damage.

Ques. My curtains smell musty but I cannot see any mould. What should I do?

Ans. A musty smell often means hidden mould behind folds or on the back side of the fabric. Check carefully and apply diluted vinegar as a preventive measure while improving airflow.

Ques. Can I dry clean curtains to remove mould?

Ans. Standard dry cleaning does not always kill mould. A specialist cleaner who uses anti-fungal treatment is a better option for proper removal.

Ques. Will mould stains come out completely?

Ans. Fresh mould can usually be removed completely. Older mould may leave stains because the pigments can bond with fabric fibres.

Ques. How much does professional curtain mould removal cost in Australia?

Ans. Curtain mould cleaning typically costs depending on size and fabric type. Delicate materials such as silk or heavy contamination may cost more.