Even after waterproofing, tent fabric can develop a greenish tinge if the protective layer wears away or if the fabric is stored whilst damp for a prolonged period. The best way to prevent this is a combination of regular re-waterproofing, storing the fabric in a dry place and keeping it clean after each use. In this article, we answer the most frequently asked questions about waterproofing, preventing mould and the correct order of cleaning and protection.
Why does green mould form on tent fabric after waterproofing?
Green deposits are caused by the growth of algae, moss and bacteria on the fabric’s surface. Impregnation does not completely stop this process, as an impregnating agent makes the fabric water-repellent but does not have an antibacterial effect. As soon as the protective layer begins to wear away, algae and mould regain a foothold on the fibres.
A water-repellent treatment ensures that water beads up on the fabric rather than being absorbed into it. However, organic particles such as dust, leaf litter and bird droppings can accumulate on the surface. This layer of organic material provides an ideal breeding ground for algae, particularly when combined with moisture and limited sunlight. As a result, green growth most often appears in shaded areas or where water collects, such as seams, folds and the underside of the tent fabric.
Storage also plays a major role. If you store a tent or awning whilst it is damp, you create ideal conditions for mould and mildew, regardless of how well the fabric was waterproofed before storage.
How long does a waterproofing treatment protect tent fabric from dirt build-up?
A waterproofing treatment protects tent fabric for one to two seasons on average, depending on how intensively the fabric is used, how it is stored and what weather conditions it has been exposed to. The more often a tent is pitched and taken down, the faster the protective layer wears away.
Intensive use, rain, UV radiation and mechanical friction gradually wear away the waterproofing. An awning that is left outside for the entire summer camping season is subjected to greater wear and tear than a tent that is only used occasionally at weekends. Practical signs that the protection is wearing off include:
- Water soaks into the fabric instead of beading up
- The fabric feels heavy when it rains
- Green or grey patches are appearing more quickly than before
- The canvas takes longer to dry after a rain shower
At the start of each camping season – including in 2026 – check whether the water-repellent properties are still intact. You can do this simply by sprinkling a little water onto the fabric. If the water beads up, the protection is still effective. If the water soaks in, re-impregnation is required.
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What are the best ways to prevent green deposits from forming after impregnation?
The most effective way to prevent green deposits forming after waterproofing is to always store the fabric in a dry place, clean it regularly and maintain the waterproofing protection. No waterproofing product offers permanent protection, so preventative maintenance remains essential.
A summary of the most effective preventive measures:
- Dry storage: Never put away tent fabric whilst it is still damp. Always allow it to dry completely before storing it, even if it has only been slightly wet.
- Rinse regularly: Rinse the cloth with clean water after each use to remove organic matter and dirt before they can cause limescale build-up.
- Store in a dry, well-ventilated place: Store tent fabric in a well-ventilated area. Avoid damp cellars or sealed plastic bags.
- Re-impregnate in good time: Don’t wait until the protective coating has completely worn off. Apply a preventative treatment at the start or end of the season.
- Avoid shady spots when camping for an extended period: Where possible, expose the canvas to the sun and wind so that it dries quickly after rain.
Do you need to clean your tent fabric before re-waterproofing it?
Yes, you should always clean the tent fabric thoroughly before re-waterproofing it. A waterproofing agent penetrates deep into the fibres of the fabric and bonds with it. If there is dirt, grime or grease on the fabric, this will prevent the impregnating agent from penetrating properly, resulting in the protective coating adhering unevenly or not at all.
Dirt and grime form a barrier between the waterproofing agent and the fibres. The result is a protective layer that peels off quickly, leaves patches or fails to repel water in certain areas. Cleaning is therefore not an optional step but a necessary preparation for an effective tent waterproofing step-by-step guide.
Allow the fabric to dry completely after cleaning before you start waterproofing it. The waterproofing agent does not adhere as well to a damp cloth, which shortens its effective life. It is best to choose a dry, overcast day without direct, bright sunlight, so that the waterproofing agent can soak in properly.
How do you remove green deposits from tent fabric without damaging the waterproofing?
Remove green deposits from the tent fabric using a specialised cleaning product for outdoor textiles and a soft brush. Do not use harsh household cleaning products, bleach or abrasive cleaners, as these will damage the fibres and completely break down the waterproofing.
For light green deposits, a mild tent fabric shampoo will suffice. Work the product in with a soft brush, leave it to soak in briefly, and then rinse thoroughly with clean water. For stubborn stains that have penetrated deeper into the fibres, a more powerful cleaner specifically designed for outdoor textiles is required.
When cleaning, please bear the following points in mind:
- Always use a soft brush or sponge; never use a hard scouring pad
- Scrubbing too hard will damage the coating on the cloth
- Always rinse thoroughly to remove any traces of cleaning product
- After cleaning, leave the cloth to dry completely in the open air
Please bear in mind that intensive cleaning will always affect the existing waterproofing to some extent, even when using suitable products. After thoroughly cleaning off green deposits, re-waterproofing is almost always necessary.
When is re-impregnation necessary after cleaning off green deposits?
Re-impregnation is necessary after cleaning green deposits if water no longer beads up on the fabric. Cleaning always reduces the water-repellent effect, particularly in the case of stubborn deposits that required a powerful cleaning agent. After every thorough cleaning, it is advisable to check the water-repellent treatment and renew it if necessary.
The water beading test will tell you for sure: after it has dried, sprinkle a little water onto the fabric. If the water beads up immediately, the waterproofing protection is still adequate. If the water is absorbed or forms flat puddles rather than droplets, it is time to re-waterproof the fabric.
In the case of light soiling that has been removed with a mild shampoo, the impregnation may still be sufficient. In the case of heavy build-up that required intensive cleaning, re-impregnation is almost certainly necessary. Do not delay this, as a fabric without proper protection will absorb moisture and quickly become affected by algae and mould again.
How Rokimi helps protect tent fabric from green mould
Here at Rokimi, we have developed a comprehensive range of products that is perfectly tailored to the steps described above: cleaning, deeper cleaning where necessary, and then effective waterproofing. Our products are ready to use, do not need to be diluted, and work on canvas, polyester and nylon.
- Hood & Tent Shampoo: Removes light green deposits, dust and surface dirt from awnings, tents and canopies without damaging the fibres.
- Heavy Duty Cleaner: For stubborn dirt that has penetrated deep into the fibres. Our most powerful cleaner is also effective against ingrained mould and black streaks.
- Hood & Tent Protection: The most effective fabric waterproofing treatment of its kind. After cleaning, this product creates a long-lasting water-repellent protective layer that shields the fabric from rain, damp and further soiling.
Whether you’re looking for a step-by-step guide to waterproofing a tent or simply want to know which product is best suited to your situation, we’re happy to help. Take a look at our full product range, discover the applications for your specific material, or go straight to the Rokimi website for more information.
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BEKIJK ALLE PRODUCTEN →Frequently Asked Questions
Can I use a standard garden hose to rinse off the tent fabric, or do I need special equipment?
A standard garden hose with low water pressure is perfectly suitable for rinsing tent fabric. Never use a high-pressure washer, as the powerful jet of water will damage the fabric’s coating and fibres. Rinse the fabric thoroughly from top to bottom and ensure that all soap or cleaning residue is completely washed away.
What’s the best way to store my tent over the winter to prevent mould?
Always store your tent completely dry, preferably loosely rolled up or folded in a breathable bag or pillowcase — never in a sealed plastic bag. Choose a dry, well-ventilated space such as a shed or attic, and avoid damp cellars. Ideally, waterproof the fabric before putting it into winter storage, so that it is well protected when the next season begins.
What if the green mould keeps coming back, even after I’ve treated the surface regularly?
If mould keeps coming back, the cause usually lies in how the tent is stored or where it is pitched. Check that the fabric is completely dry before storing it, and check whether the tent is pitched in a shady or poorly ventilated spot. In stubborn cases, a thorough clean using a Heavy Duty Cleaner may be necessary to completely remove deep-seated algae and mould spores before re-impregnating.
Can I wash tent fabric in the washing machine as an alternative to washing it by hand?
Washing tent fabric in the washing machine is generally not recommended, unless the manufacturer explicitly permits it. The mechanical action of the drum and high temperatures severely damage the coating, seams and waterproofing. Hand washing with a soft brush and a suitable cleaning product for outdoor textiles is always the safest and most effective method.
How long do I need to wait after waterproofing before I can use the tent again?
After applying the waterproofing treatment, allow the tent fabric to dry completely before storing or using the tent; this usually takes a few hours to a full day, depending on the temperature and humidity. Some waterproofing treatments, including spray products, are heat-activated; brief exposure to sunlight or a heat source such as a hairdryer on a low setting can improve adhesion. Always check the instructions for the specific product you are using.
Does a waterproofing treatment also work on older tents whose fabric hasn’t been treated for years?
Yes, a waterproofing agent can also be applied to older tent fabric, but thorough cleaning beforehand is particularly important in this case. Older fabric often has deeper layers of dirt, grime and worn-out coating that prevent the waterproofing agent from adhering properly. After thorough cleaning and drying, a high-quality waterproofing agent will adhere well even to older material and restore its water-repellent properties.
Is there a difference in maintenance between a canvas tent and a polyester or nylon tent?
Canvas tentdoek is van nature dikker en absorbeert meer vocht, waardoor het gevoeliger is voor schimmel en aanslag en vaker onderhoud nodig heeft dan polyester of nylon. Polyester en nylon drogen sneller en zijn van zichzelf iets minder poreus, maar hebben evengoed regelmatige impregnering nodig om optimaal waterafstotend te blijven. Gebruik bij voorkeur een impregneermiddel dat geschikt is voor het specifieke materiaal van jouw tent, zoals de Rokimi Hood & Tent Protection die werkt op alle drie de materiaalsoorten.