Shou sugi ban charring must be burned deeply for a number of reasons, none more important than the need to heat condition the timber below the char. Without the correct level of charring, the cell structure is not altered through thermal modification, and the carbohydrates are not burnt off.
All the finishes we do at The Blackwood Project all get an intense deep 2-3mm charring at 1060 degrees C. This thermally modifies the timber cell structure, giving a higher level of stability to the timber and making it far more bug and decay resistant.
Under charred timber cladding with faded knots within 12 months.
A light char is only cosmetic, like the old 60s hippies did to furniture with a blow torch. Aside from the thermal modification benefits, you also end up with a thin char which will erode away very quickly. The knots are the hardest part of a board to char and when this is not done correctly, they will lose their black with 12 months.
If you desire something with the benefits of shou sugi ban but without the full char on the timber, we recommend our charred and brushed finish gendai which is still black, but the surface char has been removed to reveal the undulating timber grain below. This finish gives you and best of both world by having a thermally modified timber free of char feature the timber grain.