This month Ted explains the cellular reasons why heartwood can’t be chemically treated. Therefore, when specifying sawn hardwood, it’s critical to know the natural durability class of the timber, and if it can naturally withstand the environment it’s intended for.
An informative read! found here.
Empty sapwood vessels, photo by Gary Hopewell, DAFF
Closed heartwood vessels, photo by Gary Hopewell, DAFF