Using Knots as a proxy

[plainpainter]

I have this ptp deck that I have been staining with timberoil for the past couple of years - and every spring the knots bleach out. Then a couple of days ago it hit me what was going on.

Knots in softer woods, such as yellow pine which is what pressure treated is, are much more dense than the surrounding wood. In fact the density of knots in a piece of pressure treated lumber is about equivalent to the overall density of much harder woods such as Ipe. These knots tell a story of how long we can expect a finish to last on a much harder wood species. So if I see the finish seriously 'bleaching' out in the knots after 6 or so months - that's perhaps how long I could expect an overall finish on an ipe deck to last.

Just a random thought.

[PressurePros]

Good Lord, Dan. LOL. Knots as a proxy.. that's a new one. One thing that knots have led me to believe over the years is that you need a drying oil in a stain product. That's just my opinion, hold off the slayers!

[plainpainter]

I get enough 'feedback' from folks on fading from a curing product - there is no way I would ever use a 'baby' oil stain for customers. I wouldn't be able to deal with all the calls. I personally like it for my own personal deck - just a wash and recoat every spring - and I buy into Jim's logic of what's it doing to the wood. But it doesn't fit a business model that I can think of. A.C. will have to be a 'best' compromise from here on out.

[nlightning]

I have question for dan- You mentioned Ipe` in your post and I just looked at a job this morning and the deck made of ipe` or Brazillian walnut. It has been stripped and sealed 2x and the product never seams to penetrate the wood properly and always flakes off. What on earth do you treat such a dence deck with?

[plainpainter]

Nothing lasts on ipe - you could try stripping it - don't bother neutralizing. And then tell the homeowner to let it age and grey for a year. And then come back a year later - wash and restain - that's about the best prep you can hope for.

[Beth n Rod]

Knots may be hard like Ipe, but the compositional construction is not the same. Knots are longitudinal fibers whereas in comparison with Ipe, are porous.

Knots in PTP will absorb or repel depending upon the direction of the flow when it was cut down. What you are observing is in part, an indicator of this a condition.

The density factor is due in part to the direction of the fibers vs the surrounding wood grain. Knots are also comprised of by design, higher extractive content to support the function of moving fluids through them in addition to providing support to the limbs of the tree which is a marvelous example of nature in itself to utilize its components in concentration to re-enforce the structure.

The higher extractive increases the darkness of color and in some species contributes to them becoming brittle as they dry out. Cedar and redwood for example have this in common. PTP does not necessarily due to the variations of extractives present in the wood.

Most knots will retain the color well as long as the extractive content is not of the heartwood which is less permeable to sealants. Those knots will shed the sealant faster vs the rest which will hold the sealant well which is what you have seen.

A wood Jedi you may become yet! hmm?!?

Rod!~