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Help! My house is bleeding!

posted: 31/Aug/2015

Have you ever noticed strange areas of “bleeding” coming from your pine cladded house? What you are experiencing is knot bleed.

An example of knot bleed in softwood chamfers 

All timber species contain naturally occurring extractives of one type or another – gums, resins and tannins. It is not uncommon for some of these extractives to “bleed” through paint finishes, particularly where initial moisture levels in the timber may be high, where high temperatures mobilise the extractives in the timber, or where the timber has not been sealed with a quality oil-based primer.

“Knotty” softwoods – hoop pine, Cypress pine, and other pinus species – can have high levels of resins associated with these knots (particularly knots that are dark coloured) and so can be more susceptible to this bleeding.

Our recommendation?

Seal knots with a two pack polyurethane prior to applying an oil-based primer. Applying silver frost paint or shellac to knots has also been found to help, but polyurethane remains your surest best for keeping bleeding at bay.

If knot bleeding has already occurred, scrape off excess resin, clean area with white spirits, lightly sand, apply knot sealer of choice, prime the spots with an oil-based primer and apply top coats. While there is no guarantee knots will not reappear, being vigilant about your timber maintenance should be a top priority for longevity.

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The Accredited Queensland Timber Merchant Network (AQTMN) is a group of Queensland owned and operated businesses with the aim of growing Queensland's forest and timber industry.

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