Weathering

CONVENTIONAL TIMBER COATINGS

• Weathering is required before the application of water based and urethane based coatings.
• Weathering is intended to leach out the natural oils and tannins from the timber in order
• to prepare the surface for these coatings to adhere to.
• Most products specify weathering time for up to 6 months, depending on timber types.
• Modern water based and other coatings will not adhere to natural oily and waxy timbers.
• Weathering causes tannin loss resulting in colour loss, cupping, warping and cracking.

In recent years dense Australian hardwoods such as spotted gum, iron bark etc have become very popular for use on decks and other outdoor structures almost simultaneously paint manufacturers introduced water based coatings for decks, all of which were sold in great quantities.  It was soon discovered that these water based products were peeling off the hardwood timber within a matter of weeks.  This caused great concern in the industry.  Extensive research was undertaken and it was decided to instruct all timber suppliers that all timbers needed to be weathered before applying any products.  It was found that due to the high level of natural oils and waxes in timber these new modern products could not adhere to the surface of the timber.  Two methods to weather timber were proposed: 1. To use harsh toxic chemical strippers. 2. The end user was required to expose the deck unprotected to the full weather and to hose down with water regularly for periods of up to 6 months depending on timber type.  The object to weathering is to remove the natural preserving oils and waxes as well as the timber natural colour tannins.  This practise of removing the natural oils and tannins exposes the timber to excessive levels of damaging moisture absorption resulting in cracking, cupping and warping as well as total loss of the natural beauty and colour of the timber.