Coo-Var Patent Knotting | Shellac Knot Sealer to Prevent Resin Bleed & Staining on Wood

• Seal knots and resinous areas on softwood before priming and painting
• Prevent resin bleed and staining on pine, spruce or other knotty timbers
• Achieve a fast turnaround — touch dry in 10 minutes, prime the same day
• Treat new timber joinery including doors, windows, frames and cladding before painting
• Apply a proven, traditional shellac-based knot sealer trusted by decorators and joiners

The wood surface has not been sanded and cleaned before application — surfaces must be clean, dry and free from contaminants
• You require a water-based knot sealer — this is a shellac-based, solvent-cleaned product (cleaning solvent: Thinners 6)
• The surface or air temperature is very low — low temperature and high humidity will adversely affect drying and performance

Coo-Var Patent Knotting is a low-viscosity, shellac-based knot sealer formulated to seal knotted and resinous areas of wood before priming and painting. Developed by Coo-Var — a British coatings manufacturer with over 115 years of heritage — it prevents resin and sap from bleeding through paint films, which would otherwise cause discolouration, staining and paint failure.

Knots and resinous areas in softwood — particularly pine, spruce and other common joinery timbers — contain sap that can bleed through primer and topcoat films, causing yellow or brown staining that is difficult to remedy once it has occurred. Applying Coo-Var Patent Knotting to these areas before priming seals the resin in place and provides a stable base for the paint system.

The shellac-based formula dries exceptionally fast — touch dry in just 10 minutes at 20°C — allowing priming to proceed the same day. It can be applied by brush to individual knots and resinous areas, or across the full surface of heavily knotted timber. Available in 250ml and 500ml sizes.

Key Benefits

• Prevents resin bleed and staining — seals knots and resinous areas before they can discolour paint films
• Touch dry in 10 minutes — one of the fastest-drying knot sealers available; prime the same day
• Shellac-based formula — proven, traditional formulation trusted by decorators and joiners for generations
• Interior and exterior use — suitable for internal joinery and external timber before priming and painting
• High coverage — 13 m² per litre at 75 micron DFT, cost-effective for treating large areas of knotty timber
• 115+ years of British expertise — trusted by decorators, joiners and contractors across the UK

Order before midday for next-day UK delivery.

Coo-Var Patent Knotting is an essential pre-treatment for a wide range of timber painting and joinery projects:

• New Softwood Joinery — Apply to knotted and resinous areas on new pine, spruce and other softwood doors, windows, frames and architraves before priming and painting. Prevents resin bleed that would otherwise discolour the finished paint film and require costly rework.

• Exterior Timber Cladding & Fascia Boards — Treat knotted areas on external softwood cladding, fascia boards, soffits and barge boards before applying a primer and exterior topcoat. Prevents resin bleed in exposed exterior conditions where temperature fluctuations can cause sap movement.

• Staircases & Internal Joinery — Apply to knotted pine staircases, skirtings, architraves and internal joinery before priming and painting. Ensures a clean, stain-free finish that stays looking sharp without discolouration over time.

• Garden Structures & Outbuildings — Treat knotted timber on garden sheds, summerhouses, pergolas and fencing before applying a wood paint or preservative. Prevents resin bleed on rough-sawn and knotty timber commonly used in garden structures.

• Joinery Workshops & Timber Fabrication — Use as a standard pre-treatment on all knotted softwood before priming in joinery workshops and timber fabrication. Touch dry in 10 minutes allows fast throughput without disrupting production schedules.

• Renovation & Repainting Projects — Apply to bare knotted areas exposed during stripping or sanding of existing painted timber before repriming. Prevents resin bleed on previously painted surfaces where knots have been exposed by preparation work.

If you need personalised advice on wood preparation, compatible primers or topcoats, contact our experts via the live chat for tailored guidance.

Coverage: 13 m² per litre at 75 micron dry film thickness

Note: Coverage is highly dependent on the porosity of the wood and the number and size of knots being treated. Very porous or heavily knotted timber will absorb significantly more product than smooth or lightly knotted surfaces.

Coverage per size

• 250ml: Covers approximately 3.25 m² per coat on smooth timber
• 500ml: Covers approximately 6.5 m² per coat on smooth timber

Typical usage

• Spot treatment of individual knots: a 250ml tin will treat a large number of individual knots on a standard joinery project
• Full surface treatment of heavily knotted timber: coverage will be significantly lower than the theoretical rate
• For a full set of external softwood windows and doors (approximately 5–8 m²), a 500ml tin is typically sufficient for 1–2 coats

Recommended coats

• 1 coat is standard on lightly knotted timber
• 2 coats recommended on heavily knotted or very resinous areas for full sealing
• Recoat after a minimum of 6 hours at 20°C

For accurate project planning, we recommend ordering 10–15% extra to account for surface variation and porosity.

Surface Preparation

• All surfaces must be clean, dry and free from contaminants before applying
• New wood should be sanded prior to coating to ensure an adequate key
• Clean dirty or contaminated timber with Fluxaf Power Clean before sanding and applying Patent Knotting
• Ensure all dust from sanding is removed before application

Application

1. Mix the product well before use
2. Apply by brush directly to knotted and resinous areas, or across the full surface of heavily knotted timber
3. Apply a thin, even coat — the translucent brown colour will be visible on application
4. Allow to dry — touch dry in 10 minutes at 20°C
5. Allow a minimum of 6 hours before applying primer or topcoat
6. On heavily knotted or very resinous areas, a second coat may be required — allow 6 hours between coats
7. Clean brushes immediately after use with Thinners 6

Drying Times (at 20°C)

• Touch dry: 10 minutes
• Hard dry: 3 hours
• Full hardness: 2–3 days
• Recoat interval: 6 hours

Drying times will be longer in cold or humid conditions. Low temperature and high humidity will adversely affect application, drying and performance.

Important Notes

• Apply to knotted and resinous areas before priming — do not apply over existing paint films
• Clean brushes with Thinners 6 immediately after use — do not use water
• Highly flammable — keep away from all ignition sources during application and drying
• Ensure adequate ventilation at all times

Recommended System Products

Free delivery on orders over £75 — stock up on everything you need in one go and complete the job properly.

Fluxaf Power Clean: Clean and degrease timber surfaces before sanding and applying Patent Knotting. Removes dirt, grease and surface contamination for a clean, sound substrate.

Wood Primers: Apply a suitable wood primer over Patent Knotting after a minimum of 6 hours drying time before topcoating.

Wood Paints: Apply a suitable wood paint or topcoat over the primed surface for a complete, durable wood coating system.

Paint Brushes & Trays: Use suitable brushes for Patent Knotting application. Clean with Thinners 6 immediately after use.

These products are commonly combined for best long-term results.

What is Coo-Var Patent Knotting used for?
It is used to seal knotted and resinous areas of wood before priming and painting, preventing resin and sap from bleeding through paint films and causing discolouration or staining.

What types of wood does it work on?
It is suitable for all knotted and resinous wood, including pine, spruce and other softwood joinery timbers commonly used for doors, windows, frames, cladding and fascia boards.

How quickly does it dry?
Touch dry in just 10 minutes at 20°C. Hard dry in 3 hours. Full hardness is achieved in 2–3 days. Drying times will be longer in cold or humid conditions.

How soon can I apply primer after Patent Knotting?
Allow a minimum of 6 hours at 20°C before applying primer or topcoat.

How many coats do I need?
One coat is standard on lightly knotted timber. Two coats are recommended on heavily knotted or very resinous areas. Allow a minimum of 6 hours between coats.

What pack sizes are available?
Coo-Var Patent Knotting is available in 250ml and 500ml.

How much does it cover?
Coverage is approximately 13 m² per litre at 75 micron dry film thickness, but this is highly dependent on the porosity of the wood and the number and size of knots being treated.

What do I clean my brushes with?
Clean brushes immediately after use with Thinners 6. Do not use water — this is a shellac-based product and will not clean up with water.

Is it water-based?
No. Coo-Var Patent Knotting is shellac-based and cleans up with Thinners 6, not water.

Is it flammable?
Yes. This product is highly flammable with a flash point of approximately 12°C. Keep away from heat, sparks and naked flames during application and drying. Ensure adequate ventilation at all times. Refer to Safety Data Sheet SDS 10759 before use.

Can it be used outside?
Yes. It is suitable for interior and exterior use on timber surfaces before priming and painting.

Do you offer next-day delivery?
Yes. Order before midday for next-day delivery to mainland UK addresses. Contact us for delivery options to Scottish Highlands, Northern Ireland and other remote areas.

Technical Data Sheet

Safety Data Sheet

We recommend these system products to achieve the best results with Coo-Var Patent Knotting. Free delivery on orders over £75

Fluxaf Power Clean — clean and degrease timber surfaces before sanding and applying Patent Knotting; removes dirt, grease and surface contamination for a clean, sound substrate

Wood Primers — apply a suitable wood primer over Patent Knotting after a minimum of 6 hours drying time before topcoating

Woodcare — apply a suitable wood paint or topcoat over the primed surface for a complete, durable wood coating system

Paint Brushes & Trays — suitable brushes for Patent Knotting application; clean with Thinners 6 immediately after use

Not sure which primer or topcoat is right for your timber project? Contact our experts via live chat for free, tailored advice — we will help you choose the right products and get the best result.

Fast, Reliable & Fully Tracked UK Delivery

Every order is dispatched from our warehouse using a fully tracked DX or FedEx service, so you always know when your paint will arrive.

Delivery Options

• FREE Standard Delivery (orders over £75) Arrives in 2–3 working days
• Standard Delivery – £7.95 Arrives in 2–3 working days
• Express Delivery – £13.95 Next working day delivery when you order before 12:00 noon (Mon–Thu)
• Spending £75+? Select Express Upgrade at checkout and only pay the difference

Dispatch & Delivery Times (What Happens After You Order)

• Express delivery (order before 12:00 Mon–Thu) Dispatched same day, delivered next working day
• Standard delivery (Mon–Wed orders) Dispatched next working day, delivered 2–3 working days later
• Orders placed Thursday (standard delivery) Dispatched Friday for Monday delivery
• We do not dispatch or deliver on weekends or UK bank holidays

What to Expect on Delivery

Please provide a contact telephone number at checkout. This allows the courier to share tracking updates or contact you if there are any delivery issues.

Most orders require a signature on delivery. If you may not be available during the day, we recommend delivery to a workplace, business address, or another location where someone can sign.

Outside the UK Mainland?

Delivery prices shown apply to UK Mainland only.

For the Highlands, Islands, Northern Ireland, or non-mainland addresses, please contact us for a quick personalised quote via live chat, by calling 01482 222 421, or emailing info@specialistpaintsonline.co.uk.

Bottom Line

Order today, get fast and reliable delivery, track every step, and get painting without delays.