It has come to light recently that the extremely fine milling process used in the manufacture of thermally modified woods creates such a smooth surface that little in the way of coatings can adhere to. Coatings need surface roughness to adhere for any length of time. Tints that are available for example, with the Cutek Extreme clear could erode prematurely when applied to thermally modified wood surfaces as a result. No form of pigment can penetrate into wood or into wood cells. The oxides reside on the surface only. That is why the rougher the surface the better. Rough cut beams and siding for example will hold color much better and longer than a fine sanded or planed surface. #80 grit sanding is what is recommended to remove mill glaze and provide more of an “overall” surface in order for coatings with a color component to better adhere for any period of time. Best to simply apply Cutek Extreme clear both as a surface treatment and end-cut treatment in order to minimize checking and cracking, and allow the wood to silver to a beautiful patina.
The picture on the left shows what can occur in under a year, when a coating is applied too thickly and not allowed to cure.