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Prevent Wood Knot Staining (Pine)

February 24, 2017


Ever had wood sap bleed through your paint job even though you primed?  Pine wood, which is commonly used in building, is a real culprit especially if painting with more user-friendly water-based paints.  Here’s a sure-fire method to help you zap the sap and never have a costly repaint again.


The knots in softwoods such as Pine tend to bleed, oozing resinous sap and wood extracts that can cut through even a good quality primer and leave unsightly stains effectively ruining the paint work.


Don’t let knotty pine drive you nuts.
1.    First remove any surface sap with white spirit or puritene thinners.
2.    Spot prime the knots with an alcohol-based shellac primer which has excellent stain blocking properties and will seal out both oils and water.  Cover generously or apply more than one coat.
3.    Prime the entire wood area to be painted with a good quality wood primer such as Ulttima Wood Primer. This will seal the rest of the bare wood and create a uniform surface for your top coat.
4.    Finish with the top coat of your choice.

To Repair Bleed Through

Depending on the extent of the staining and how knotty the pine is, repair can be painful and you might effectively have to redo the whole job.  Sand down the areas where there is staining and apply the shellac stain blocker over the knots and then reapply the top coat.  You will likely have to repaint edge to edge to avoid flashing.



Check out our other great articles in this February edition of Paint Pro!


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