You could be forgiven for thinking designer Steven Banken created the piece below by stocking up on a selection of MinWax stains:
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Instead the Eindhoven graduate, who shares a studio building with Piet Hein Eek, went Walter White and created the gradations via chemistry.
As Banken explains,
Oak contains high concentrations of tannic acid, which turns into dark blue when it's exposed to steel. The same happens with steel, as a result of a chemical reaction between red iron oxide and tannic acid. To accelerate this normally undesirable process the elements that cause this chemical reaction are applied in liquid form on the other material.
Below is Banken's maddeningly short video showing snippets of the chemistry; there isn't much in the way of instruction, so those interested in pursuing the procedure will have to pull a Jesse Pinkman and start experimenting.