All knives are graded for hardness. The harder the steel in the blade, the longer the knife stays sharp for and the more exquisite the cutting edge feels.

In contrast, the softer the steel, the quicker it blunts and it doesn’t ‘feel’ as sharp, even when it’s brand new out of the box.

For many years, knife manufacturers have been trying to use increasingly harder steel in order to achieve the ultimate cutting edge. The hardness of stainless steel is measured on a scale called Rockwell; Rockwell 62 º (also known as HRC62) being the highest grade commercially available. However, the brittleness of such hard steel has always been a limiting factor – therefore knife manufacturers have had to stop short of what is considered ‘the ultimate steel hardness for a knife’.

Standard single layer Japanese knives will typically rate at between Rockwell 54 -58 º. This is the outer limit of steel production as any higher would result in snapping or chipping of the blade if misused.

I.O.Shen Mastergrade knives have overcome this problem by using a layer of extremely hard Japanese steel (Rockwell 62º), which is sandwiched between two layers of softer stainless steel (Rockwell 10º), to produce the ultimate cutting edge. The softer layers add a protective shock absorbing element to the blade, whilst the HRC62 steel which runs through the middle is exposed at the edge of the blade to ensure that your knife is the sharpest blade that can possibly be manufactured.

CATRA (The Culinary & Allied Trades Research Association) are word renowned for their steel testing and consultancy services. I.O.Shen knives have been tested and certified as “Excellent” for initial cut and longevity of cutting edge.