Our 3-step guide shows you how to prime and seal troublesome knots and resinous timber with ease.
Knots in wood are full of sap which seeps to the surface and will bleed and show through paint. Our guide below shows how to use Zinsser products to properly seal knots and block resin from penetrating to the topcoat so that you won’t have to strip wood back after an unsuccessful project, saving time and money.
Zinsser listens to contactors and develops new products – or adds features to existing products – to meet their changing needs, delivering world class products that meet “real world” challenges, providing tried and tested solutions to painting problems, such as painting knots and resinous timbers.
Step 1. Surface Preparation
Ensure the knotted and resinous timber surface is clean and dry, free from anything that will interfere with and affect the adhesion and application of the Zinsser products materials to be applied.
Scrape away loose and failing material to a sound edge or use a hot air stripper, then feather the sound edges with a fine grade abrasive paper.
Prior to painting, the moisture content should not exceed 18%.
Remove all dust before removing all visible signs of organic growth, using Zinsser Mould Killer & Remover (in accordance with the manufacturer’s instructions) to treat affected areas and allow to dry.
If any sound paint remains, remove any remaining contaminants by cleaning the area down with Zinsser Universal Degreaser & Cleaner and rinse thoroughly with clean water to remove all residues, letting the surface dry.
Fill any cracks and small surface defects with a suitable filler in accordance with the manufacturer’s instructions and allow the area to dry before rubbing down with a fine grade abrasive paper and then remove all dust.
Step 2. Knots
Use a hot air stripper to remove excess resin from knots and other resinous timber, then wipe immediately with methylated spirit to remove residue.
Spot prime knots with one full coat of Zinsser B-I-N in accordance with the manufacturer’s instructions and allow a minimum drying time of 45 minutes in normal drying conditions.
Step 3. Resinous Timber
Prime resinous timbers overall with one full coat of Zinsser Cover Stain in accordance with the manufacturer’s instructions. Allow a minimum drying time of 2 hours in normal drying conditions.
Step 4. Decoration
For interior timber projects, decorate with two full coats of Zinsser Perma-White Interior. The paint is available in Matt, Satin or Semi-Gloss finishes with over 350 colour options – apply in accordance with the manufacturer’s instructions and allow a minimum drying time of two hours between coats.
Decorate exterior woods with two full coats of Zinsser AllCoat Exterior Satin/Gloss in accordance with the manufacturer’s instructions, choosing from over 350 colours from RAL and BS shades. Allow a minimum drying time of one hour between coats.