Yellow poplar - logs to siding

Torrefied Yellow Poplar: Caramel Stain

The lion's share of Torrefaction BTM's torrefied wood for outdoor siding and terraces is yellow poplar or liriodendron tulipfera (tulip tree); a soft hardwood. In fact, it's not from the poplar family at all, it's part of the magnolia family and was simply misnamed at it's origin when European settlers came to America.

Yellow poplar is a great species to use; it grows fast, it's a strong wood, it's quite straight and there are not many branches (therefore not many knots). Deborah A. Boerner-Ein wrote a nice article on yellow poplar, praising it's virtues as a sort of forgotten or disregarded species.  For torrefied wood, the reason is simple - aesthetic beauty. Once torrefied, the wood grain patterns are actually quite stunning - as you can see in the funeral home photo. There are so many colour variations and shades within every plank that the "look" yellow poplar gives us is unique.

Yellow Poplar: At the sawmill

Why is there such variation in the yellow poplar planks?

One factor has to do with the wood - colour variations between the sapwood (what you see as a beige ring) and the heartwood (what you see as a darker centre) are great and non-uniform. This is obvious from the photos of yellow poplar logs on the left.

A second factor has to do with the torrefaction process. The torrefaction (or roasting) process amplifies the wood grain variations in all woods. Hence enhancing their appearance.

The third and final factor is in the use of stains that further enhance the colour variations. Just as some stains help us subdue the variations to provide a more uniform look, others enhance them.