The mild steel and stainless steel react differently to the heat treatment, giving the Carbon bench an iridescent blue and pale yellow finish.
To create the product, Wijnant welded a pattern of raised welts onto thick slabs of steel and stainless steel.
As the slabs heat up in a tempering oven, a film of iron oxide forms on the surface of the metals. The colour changes according to the temperature and the type of steel.
Mild steel turns blue while stainless steel, which is enriched with chromium to prevent corrosion, turns yellow.
"Normally, steel all looks the same and then when you put it in the oven, you get these crazy, hidden colours," Wijnant told Dezeen. "It's all fired on the same heat. But, the steel turns blue while the stainless steel turns a light yellow."
The pattern on the bench's surface was initially traced with a pencil, like a "hand-drawn painting of wood".
Wijnant then used a TIG welding machine to create a raised, textured finish using either steel or stainless steel welding rods, so the base and the linework end up being cast in matching or contrasting colours.
"I really wanted to create a more organic object, because steel is normally super hard and straight," he said. "I want to change this perception."
Finally, the steel bars were bolted together to form the bench.
Wijnant, who is an alumnus of the Design Academy Eindhoven, plans to create an entire collection of furniture around this process, playing with the range of colour and texture combinations that can be created using this one material family.
Italian furniture brand De Castelli has previously made use of the oxidisation process, together with etching and polishing to create a series of storage solutions that show off the versatility of metal.
Similarly, Alessandro Zambelli created a series of furniture from a puzzle of small metal pieces, each oxidised to a different shade.