This planter made of a material that is almost pure carbon steel but processed in order to have a protective layer on the surface to make it weather-proof. The surface is originally reddish-brown (resembles the colour of rusting), which becomes darker within time. If used properly, this planter is expressive, durable and maintenance-free and can stand time in its own peculiar way. When this planter gets wet and then dries out, the rust layer becomes a little thicker, while the underlying solid steel becomes thinner.