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Apply to interior wood to stop knots showing through paint.
Features
- An all-in-one white primer and undercoat for a long lasting knot-free base
- Prepares bare and previously painted interior wood for top coat paints
- Stops wood knots and wood resins showing through your paint
- Covers bold colours, dark marks and helps paint to stick
- Low V.O.C content
Brand
Drying time
4 hrs
Coverage
Up to 12 m2 per litre
No. of coats
2
Size
250ml
750ml
2.5L
MPN
Please Select Size/Option
GTIN
Please Select Size/Option
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Overview
Overview
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Ronseal Knot Block Wood Primer And Undercoat is perfect for preparing bare and previously painted interior wood for painting.
- Looking for an alternative stain blocking solution? Try Ronseal One Coat Stain Block
- Looking for a one coat primer and undercoat for wood? Try Ronseal One Coat Wood Primer and Undercoat
- For other types of interior surfaces, use Ronseal One Coat All Surface Primer and Undercoat
- For exterior surfaces, see Ronseal All Surface Primer and Undercoat - Exterior
Preparation
Preparation
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Ensure that wooden surfaces to be treated are clean, dry and free from dirt, dust and any other surface contaminants. Make sure the room temperature is above 10°C. Put down dust sheets to cover any areas that do not need painting.
- Lightly sand wood using 120 grit sandpaper in the direction of the wood grain to give it an even finish
- Vacuum and wipe wood over with white spirit, being sure to remove any sanding dust, prior to painting
- Any instances of wet rot can be treated with Ronseal Wet Rot Wood Hardener, and any existing woodworm can be eradicated with Ronseal Woodworm Killer
- Fill any holes or cracks with Ronseal High Performance Wood Filler or Ronseal Multi Purpose Wood Filler
Application
Application
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Always do a small test area before beginning any project to assess performance. Follow the manufacturer's instructions on the tin at all times. Stir the contents of the tin thoroughly prior to use.
- Apply Knot Block Wood Primer using a good quality synthetic brush in the direction of the wood grain
- Allow 4 hours to dry, then apply a second coat
Finishing
Finishing
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Once fully dry, Ronseal Knot Block Wood Primer & Undercoat can be over-coated with Ronseal Stays White Ultra Tough Paint, Ronseal Stays White One Coat Non Drip Paint or Ronseal Diamond Hard Floor Paint.
F.A.Q.
F.A.Q.
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When using this on a shed, should I paint both sides of the slats or just the outside?
Can you successfully spray Ronseal Knot Block Primer and Undercoat with an airless sprayer?
This product is only suitable for interior use and can't be used on a shed. If you are after an external knot blocking primer, consider a knotting solution such as Barrettine White Knotting followed by Protek Stain Blocking Primer
Can you successfully spray Ronseal Knot Block Primer and Undercoat with an airless sprayer?
We do not recommend spray application, it is best suited to brush or roller application.
Datasheets
Reviews
Reviews
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18 customer reviews
5.0/5.0
based on last 18+ months
5 stars
15
4 stars
3
3 stars
0
2 stars
0
1 star
0
Great product would recommend
This was recommended by a master carpenter, so had every faith it would do the job it was intended for. Easy to apply, low odour and with two coats gives good coverage. Would definitely purchase again and have done just that.
Mrs K Rollason. , 2.5L (19/08/25)
Good product
Covers knots - does what is says on the tin. You will need two coats.
K Moulder. , 2.5L (30/06/25)
Happy with service provided
Very happy with product and service provided
Vishram Harji. , 2.5L (14/06/23)
Great paint
Seems quite thin but I guess that is to soak into the wood to stop the knots showing. Quick sand when dry and ready for 2 coats of top coat. Very pleased with results
Adam. , 2.5L (05/01/22)
Works just as it says on the tin
I had painted a new large pine summer house with primer, undercoat and semi-gloss paints, never thought about knots in the wood, 12 months later hundreds of knots showed through the paint, it looked awful.
Found Ronseal Knot Block advised as a remedy, used 2 coats on top of existing paint, then a coat of semi- gloss with perfect results, no sign of knots anywhere, now very pleased with finish, Knot Block does just what it says on the tin, even on previously painted wood, would recommend its use to everyone, just wish I had Known about it and used it on the bare wood and saved all that work and expensive paint.
Ron P. , 2.5L (14/11/21)
Too early to enthuse
Not yet sure that this will block knots adequately. it is a different formulation now and it will be at least 12 months before I know whether there is discolouration
John Waters. , 2.5L (15/09/21)
Easy to apply and does the job
Good coverage,quick drying,stops knots from reappearing once overcoated with stay white ultra gloss
Ian Rollinson. , 2.5L (06/07/20)
Does exactly what it says on the tin
Bought this for new skirting board and it works perfectly.
John Appleton. , 750ml (22/06/20)
Does what it says
Use two liberal coats to fully seal
Charles Whittle. , 750ml (24/05/20)
Does what it says on the tin!
Does what it says on the tin!
Pamela Crawshaw. , 2.5L (15/04/20)
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