Categories: All Products, All Products, Cleaning Chemicals, Gk Products, Timber Treatment, Wood Sealer

Tags: 5l, Professional Grade

GK Invisible Wood Sealer 5Ltr

Name: GK Invisible Wood Sealer 5Ltr
Brand: GKProductsUK
SKU: CHE / R28/10 / 5LTR
Price: 21.60 GBP
Availability: InStock

SKU: CHE / R28/10 / 5LTR Brand: GKProductsUK

£21.60 Ex VAT: £18.00

GK Invisible Wood Sealer is a professional-grade, water-based wood sealer and waterproofer that penetrates deep into timber to create a durable moisture barrier from within.

Completely clear once absorbed. Algae-repelling. Safe on decking, fencing, garden furniture, and all outdoor timber structures. Ready to use with no dilution required. One 5-litre bottle covers up to 25 square metres.

What Is a Wood Sealer and Why Does Outdoor Timber Need One?

A wood sealer is a penetrating treatment applied to timber to prevent moisture from entering the wood's grain and pore structure. Unlike surface coatings such as oils, stains, and varnishes that form a film on top of the timber, a penetrating wood sealer absorbs into the wood itself and creates a waterproof barrier from within. There is no surface film to crack, peel, or trap moisture beneath it, and the wood's natural appearance is completely preserved.

Outdoor timber without moisture protection deteriorates progressively. Water entering the grain causes swelling and contraction through wet and dry cycles, leading to warping, splitting, and cracking. Persistent moisture enables fungal and biological growth of algae, mould, and wood-rotting fungi that discolour the surface, accelerate decay, and eventually compromise the structural integrity of the timber.

A quality wood sealer and waterproofer applied before these problems develop is far more effective, and far less costly, than restoration after the fact. GK Invisible Wood Sealer is a professionally formulated, water-based wood sealer designed specifically for outdoor timber in the UK climate, delivering deep-penetrating waterproof protection with a genuinely invisible finish and an algae-repelling formula.

Invisible by Design

The defining characteristic of GK Invisible Wood Sealer is what it doesn't do to the wood's appearance. Once absorbed, the sealer leaves no visible sheen, no surface film, no tint or colour shift. The wood returns to its original, natural appearance while benefiting from deep waterproof protection that is completely invisible to the eye.

This makes it ideal for pale decking boards, silver-grey hardwood furniture, natural oak fencing, fresh-sawn cladding, or any timber where the natural colour and character matters.

Waterproof Protection With Algae-Repelling Formula

GK Invisible Wood Sealer combines moisture protection with an algae-repelling formula, providing a dual layer of defence that standard wood sealers don't offer. In the UK climate, outdoor timber in shaded or north-facing positions is particularly susceptible to green algae and mould. Algae doesn't just discolour the wood, it holds moisture against the surface, accelerating biological decay and, on decking, creating a hazardous slippery surface.

The algae-repelling component actively resists biological growth on treated surfaces, keeping timber cleaner between maintenance cycles and reducing the frequency of deep cleaning required.

Where GK Invisible Wood Sealer Can Be Used

Decking: all softwood and hardwood decking boards. Safe for decking use and will not increase slip risk. Allow 24 hours before heavy foot traffic.
Fencing: panels, posts, rails, and gates, treated or untreated timber.
Garden furniture: benches, chairs, tables, planters, and raised beds, including previously indoor furniture being prepared for outdoor use (apply two coats and avoid extended direct sunlight exposure).
Pergolas, arches, and garden structures.
Cladding and external joinery: timber window frames, door frames, and cladding boards. Not a substitute for paint or stain on painted joinery, but effective as a pre-finish moisture treatment on bare timber.
Sheds and outbuildings.
Bird boxes and garden accessories: safe for external surfaces. Leave perches and entrance holes untreated.

Deep Penetration, Not a Surface Film

GK Invisible Wood Sealer absorbs into the timber's grain and pore structure rather than sitting on top of it. This creates a moisture barrier from within the wood, so there's no film on the surface that can crack, peel, or trap moisture underneath.

The Water Bead Test

Once dry, the sealer causes water to bead and run off the treated surface rather than soak in. This beading effect confirms the moisture barrier is active, and it's also the most reliable way to know when reapplication is due. When water stops beading and starts soaking into the wood, it's time to retreat.

Wet-on-Wet Application

A second coat is applied before the first coat dries, allowing both coats to work together deeper into the grain. This wet-on-wet method maximises penetration depth and ensures full coverage of the pore structure.

Algae Resistance

The algae-repelling formula works alongside the moisture barrier to actively resist biological growth establishing on the treated surface, keeping timber cleaner for longer between maintenance cycles.

Penetrating waterproof wood sealer and waterproofer: absorbs deep into the wood grain to create a moisture barrier from within, not a surface film that can crack or peel
Completely invisible finish: no sheen, no tint, no surface change
Algae-repelling formula: actively resists biological growth on treated surfaces
Ready to use: no dilution required, apply directly from the bottle with a brush, roller, or low-pressure sprayer
Wet-on-wet two-coat application for maximum penetration and durability
Safe on decking: does not increase slip risk
Covers up to 25m² per 5-litre bottle depending on surface porosity and application method
Water-based, professional grade: formulated for UK outdoor conditions, 24-month shelf life
Touch dry in 2 hours, fully dry in 24 hours

Ready to use straight from the bottle. No dilution, no mixing, no primer coat required. Shake the container well before use, then apply with a brush, long-pile roller, or low-pressure garden sprayer.

Apply a generous, even first coat to saturation point
Apply a second coat wet-on-wet before the first coat dries
Remove any excess with a clean, lint-free cloth to avoid runs, drips, or pooling

Drying Times

Touch dry within 2 hours. Fully dry and ready for light foot traffic within 24 hours. For decking and flooring, allow the full 24 hours before heavy use.

Coverage and Storage

One 5-litre bottle covers up to 25 square metres depending on surface porosity and application method. Highly porous or rough-sawn timber will absorb more product and reduce coverage per bottle. Store in a cool, dry place in the original container. Shelf life is 24 months from manufacture.

For best long-term results, clean timber with GK Pro, GK Greener Kleener, or GK Concentrated Fungicidal Wash before any reapplication.

Download Spec Sheet PDF Download Spec Sheet PDF

Frequently Asked Questions

GK Invisible Wood Sealer penetrates into the pore structure of timber and creates a waterproof barrier from within the wood. This prevents moisture from entering the grain, which is the primary cause of warping, cracking, biological growth, and rot in outdoor timber. Unlike surface coatings, GK Invisible Wood Sealer doesn't form a visible film on the surface, it works invisibly from inside the wood.

Yes. GK Invisible Wood Sealer provides both sealing and waterproofing in a single treatment. It penetrates deep into the timber to create a moisture-repelling barrier that causes water to bead and run off the surface rather than soaking in, while also sealing the pore structure against biological contamination. No separate waterproofer is required.

Yes. GK Invisible Wood Sealer is suitable for decking and will not increase the risk of slipping. Allow 24 hours of drying time before returning furniture or allowing heavy foot traffic onto the treated surface.

The water bead test is the most reliable indicator. Splash water onto the treated surface, if it beads and runs off, GK Invisible Wood Sealer is still performing. If the water soaks into the wood rather than beading, it's time to reapply. In most conditions, annual reapplication is sufficient to maintain consistent moisture protection.

Yes. Provided the furniture receives at least two wet-on-wet coats as recommended, there is no reason it cannot be used outdoors after treatment. Note that GK Invisible Wood Sealer should not be considered primary protection against sustained exposure to direct sunlight. For furniture in full, unshaded sun, a UV-protective decking oil or stain may provide more appropriate long-term protection.

Yes. GK Invisible Wood Sealer is safe for the external surfaces of bird boxes. Leave the perches and entrance hole untreated to ensure nothing is transferred to the interior where it could come into contact with birds or nesting material.

Apply with a brush, long-pile roller, or low-pressure garden sprayer. Shake the container well before use. Apply a first coat to saturation, then apply a second coat wet-on-wet before the first coat dries to maximise penetration. Remove any excess with a clean, lint-free cloth to prevent runs or pooling. Touch dry in approximately two hours, fully dry after 24 hours.

Why us

Why Choose GK?

We believe in constant innovation. Our team is dedicated to finding new and better solutions that the industry needs, providing the most effective, least harmful, and safest professional-quality products to our customers.

We use high-quality active ingredients that deliver superior, longer-lasting results. By avoiding harsh chemicals, we ensure a safer cleaning process for surfaces and substrates, as well as for the environment. Whether you're an industry professional or a DIY enthusiast, you can expect our products to provide a thorough, lasting clean that leaves your surfaces pristine.

So if you're tired of products on the market delivering a sub-par clean, want to experience professional-quality results, or even find comfort in knowing that your cleaning products are safer for your surfaces and the environment, then why not try our range of GK cleaning products for yourself?

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