The secret sauce is ammonium chloride. They mixed up a batch of an ammonium chloride solution, made a custom stamp (in this case the Make logo), and then essentially stamped the solution, just like you would stamp ink, onto the wood. Once you’ve stamped the wood, you heat the surface with a blow dryer or heat gun and the heat activates the solution, burning the surface of the wood. Using this technique you can create significantly more detailed designs than you would be able to using a hand tool and without the expense of ordering a pricey custom branding tool.
Hit up the link below for additional details.
Chemical Wood Burning [Make Projects]