The Nature of Japanese Carbon Steel Woks/Frypans
Takumi carbon steel is high purity steel. It is important to understand its nature.
Its original colour is silver. Once we put the wok into use, the carbon steel will expand and absorb cooking oil. In a few months, the colour of the wok will gradually turn to black with oxidized protective layers covering the entire wok.
Please find the following images helpful to understand the process.
Decades ago, many Japanese brands started to produce its woks/frypans using a high-speed heating and oxidation process in its factory, which turned the cookware from silver to black. This made their woks/frypans ready to use right away. The goal was to save users time by immediately providing a non-stick cooking surface (with proper heat and oil, of course).
Users may find that the instructions for all Japanese carbon steel woks/frypans (including Takumi, River Light and Yoshikawa) do not recommend that the user wash the cookware with detergent. This is to avoid washing away the oil layers.
From our own experience, we know that we can wash the wok/frypan with detergents and steel wool without any issues.
Do NOT Scratch Too Hard
If the wok was burnt, it is recommended that we bring the wok to boil with water. The burnt residue should easily come off. Even if we scratch hard enough to peel off the protective oil layer, no permanent damage is done. Simply maintain it with oil again and we will see the wok turn black again over the course of a few months.
Users may find black residue every time we wrap the pan with a paper towel. This is the evidence of carbon steel oxidation. The product is scratch-resistant during normal use.