The torrefaction process involves baking wood in an oxygen free environment at temperatures higher than conventional timber seasoning kilns. Taken to its logical conclusion you would end up with charcoal but stopped short, the wood merely darkens depending on how long it has been roasted.
This colour change occurs due to chemical reactions between the wood’s proteins and its natural sugars, and torrefied maple can range from soft amber to a deep reddish brown that is closer to cherry or even walnut.
The Vikings used torrefied wood because it absorbs less moisture so size and shape are more likely to remain consistent after it has been sawed and planed. In other words it’s stronger and more stable as well as being lighter, which means it’s equally well suited to shipbuilding, wooden flooring and pool cue making.