筋 - Suji  

Suji Lines 1.jpg

Suji, or hairlines - are common in most Suita. They can be viewed as a type inclusion, but most users will just refer to them as lines. Suji are ‘safe’ hairlines in the sense that they will not harm the steel, and we can hone on them without issues. Often, these lines are made up of the same mineral deposits that create the Lotus Blossom pattern known as Renge.  However, this is not always the case, and it’s important to remember that the minerals in Suji can be wildly different from one stone to another. Never assume, carefully test each stone for its intended purpose.  

Kesuji are toxic lines, and they can be present also. These can almost always be identified by a ‘tick’ sound when a blade passes over them. That sound is the result steel hitting a material that is very hard. Kesuji can damage edges, scar bevels, and ruin hours of hard work. Sometimes, these toxic lines can be cut away or scratched out with a nail or awl. Remember – the presence of one Kesuji means that there may be more toxic particles hidden in the stone. 

It should be noted that the presence of many Suji on the working surface of the Suita may make for a beautiful pattern. However, with extended periods of heavy use, those lines can become liability. Water can enter the stone through those crevices; over time that moisture can lead to the stone becoming too soft, or prone to fissuring. This is not always the case, but it is certainly always a possibility.

Renge Side.jpg


© Keith V Johnson 2014 - 2018