Just wrapped up a big Shou Sugi Ban project for a client

I did a similar project last fall on some 1x8 cedar planks for an outdoor feature wall. Getting that even char with a standard propane torch is definitely a test of patience; I ended up switching to a high-output weed burner to speed things up on the larger surfaces. One thing I found was that the carbon layer can be really finicky depending on the moisture content of the wood. If it's too wet, the grain doesn't pop as much and you just get a muddy soot. When I got to the finishing stage, I actually skipped the standard poly and went with a few coats of Watco Danish Oil before sealing it. I felt like it soaked into the char a bit better. For the window installs, I used black GE Silicone II instead of clear. It blends into the burnt texture perfectly so if you have a tiny bit of squeeze-out, it’s basically invisible against the dark wood. Dealing with the smell is the worst part—I had to keep my shop fans running for a week straight just to get the fumes out.

I’ve had a diferent experiance with the finish on my burnt wood projects. A few years back, I used a high-build polyurethane on some charred Douglas Fir shelving, but I found that over time, the plastic-like film tended to mask the actual tactile feel of the grain. Nowadays, I ussually skip the poly and go with a few heavy coats of Tung oil or even somethig like Penofin Blue Label. It takes longer to cure, but it penetrates the carbonized layer rather than just sitting on top, wich I find keeps the deep blacks from looking "muddy" under bright interior lights.

When I’m prepping the boards, I usually hit them with a stiff brass wire wheel on my angle grinder instead of just a light brush. It pulls out the softer springwood and leaves the harder grain standing in high relief. For the windows, I’m always cautious about the heat absorption. Those dark, charred frames can get incredibly hot if they’re in a south-facing room, so I typically leave a 1/8 inch expansion gap. I’ve started using EPDM gaskets instead of just relying on silicone alone beacuse the thermal movement on burnt pine can be pretty aggressive compared to untreated lumber.

I found that using a stiff nylon brush right after torching worked best. I tried a wire brush once, but it chewed up the soft pine grain too much. If you don't get every bit of that loose soot off, the finish can end up looking muddy. I also started thinning my first coat of poly by about 20%. It lets the finish soak deep into the char instead of just sitting on the surface. It relly helps bond that burnt layer to the solid wood so it doesn't flake off later if it gets bumped.

I’m curious if you accounted for the significant resin weepage that often plagues species like Southern Yellow Pine when subjected to those high temperatures, as I've found that if you don't aggressively scrape the pitch pockets before applying your topcoat, the heat from the sun can eventually cause the resin to liquefy and push right trough your polyurethane film, creating unsightly bubbles. Regarding the fixed windows, I typically prefer using a EPDM gasket system for charred frames rather than relying solely on chemical sealants, primarily because the irregular, carbonized surface of the wood can sometimes lead to micro-voids where the silicone fails to acheive a truly hermetic bond during seasonal expansion cycles.