Why Do You Torch Wood?

It resists moisture. The charring process leaves behind a two- or three-millimeter layer of char on the surface that shields underlying wood from water and water vapor, keeping it from eroding or absorbing moisture and swelling, warping, or rotting.

What is the purpose of charring wood?

The charring process makes the wood resistant to fire, insects, fungus, rot, and (as recently discovered) harmful UV rays. That means that Yakisugi wood will not weather or fade when exposed to sunlight.

Does charring wood make it stronger?

Yes, the charring can make wood slightly harder, but it becomes so much more brittle and weak that there's little overall improvement of the weapon. ... There it was sealed away from the elements and preserved far longer than wood ordinarily can be.