White Paper Steel called as Shiro-gami

White paper steel called as Shiro-gami is Yellow paper steel called as Ki-gami from which further impurities such as sulphur and phosphorus have been removed. Ki-gami is based on the composition of SK material mixed with approximately 50% iron sand, Shiro-gami is made of 100% iron sand. Because of its purity, the temperature range for hardening in the forging process is narrow and it is difficult to achieve optimum hardness. This requires a high level of forging skill and is therefore expensive. The difference between Shiro-gami No. 1, No. 2 and No. 3 is the difference in carbon content. The higher the carbon content, the harder the iron becomes, with Shiro-gami No. 1 being the hardest but also the hardest to sharpen. Shiro-gami No. 3 is often used for household purposes, while No. 1 is often used by chefs.

Shiro-gami No. 1 becomes extremely sharp when sharpened and has been called ‘the best knife’.

(Source: How to select, use, grow for knives and whetstones. Shibatashoten Co., Ltd.)