Application of Cutek Extreme on Thermally Modified Woods.

The roasting & steam process creates a very appealing initial look to woods.  However, these woods will now silver in record time, are far more brittle, and they can aggressively check & crack.  If thermally modified wood is left uncoated in Australia it will shift in color to something much lighter inside 7 days when in full sun! 

Thermally modified woods in general have been reduced to an unnatural 0% moisture content and as a result are very thirsty.  As tempting as it is to put on a thick wet looking coat, only very thin coats should be applied and allowed to dry thoroughly in between.  Thermally modified woods readily accept oil based coatings ONLY.  (Water based emulsions reside primarily on the surface and provide much less oil protection overall).  Cutek CLEAR is the ideal treatment and is recommended by several of the manufacturers, mills and distributors of thermally modified woods. Pre-coating with CLEAR on all sides is recommended to help control the checking & cracking aspect.  You should expect to get 350 – 400 sq. ft. per gallon, and as tempting as it may be to apply lots of material per coat, only thin coats should be applied in order for adequate overall drying time.

Most of the mills we have spoken with, feed the material through their final planer process slowly & use high speed blades.  The wood comes out at times almost as smooth as glass with less surface area than even Ipe for pigment to adhere to.  (The equivalent of mill glaze on softer wood species).  There is at times blade chatter seen too.  The problem with the highly polished surface is that it will hold very little Colortone pigment when first applied.  Most of the CUTEK Extreme oil will migrate into the wood leaving very thin trace amounts of our pigment to try and adhere to the shiny polished surface.  Thermally modified woods should be first sanded with #80 grit in order for the pigments to have a chance of adhering.  Again, THIN coats with adequate drying time in between will provide the longest possible presence of pigment and the pigment is designed to wear off as opposed to creating a skin that has to be sanded off.  Sanding wood with #80 grit is an important step regardless of what exterior wood coating is used.  Nothing sticks well to shiny, smooth surfaces.  Cutek Extreme also has the advantage of being able to be applied in the heat of the day.  In fact, the hotter the better.

If the customer insists on using with a Colortone: 

Cutek Extreme with Colortone is to be power stirred /blended for min. 3 minutes prior to use, and every 10 -15 minutes during use as the tint oxides will settle out otherwise.  Do not relay on shaking the tins like paints – it is not sufficient! 

Decks with tinted Extreme may look tired, dirty and scratched over time, but they will come back to life with a good cleaning.  We recommend cleaning with ProClean, following the application instructions:

1) wet the wood thoroughly.

2) apply ProClean to the wet wood and agitate with a soft bristle broom or brush.

3) allow to sit for 1 – 2 hours and rinse off using a pressure washer set to fan mode & keeping the sprayer 8 – 12″ above the deck surface.

4) once completely dry, apply 2 thin coats of Cutek Extreme allowing for adequate drying time in between. 

When you use the ProClean and pressure washer to rinse off, it is very likely a lot more pigment will come off, as there doesn’t seem to be good adherence to the early wood. If portions of the deck feel too smooth, please roughen with #80 grit sand paper.  Re-coat with the Cutek Extreme, remembering to stir the container thoroughly every 10 – 15 minutes if you are using a Colortone.

It is the manufacturers opinion that any hardwood deck in North America that has been in full weather for 12 months, will require a good clean and re-application of Cutek Extreme to bring it back to life.  This should be the reasonable expectation. To expect a full weather exposed Cutek Extreme coated deck to stay looking good for two to 3 years would be an unreasonable expectation. 

Again, the CUTEK system is not low maintenance, it’s easy maintenance. 

I hope you come to like it as much as we do.

This article was written by Dave Bartnik from Deck Source in Betton, Ontario and we want to thank him for his insight on this topic.

CFP Cladding & Decking thermally modified wood siding just before being installed on a Toronto, Ontario home. The species is North American White Ash.

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