My most-used Hokujo kyusu (which I had kept at my family home in Annapolis for the last five years) developed a black film, mostly over the large sesame filter—probably because I didn’t rinse it after use with boiling water during those years. So I decided it was time for a Sodium Percarbonate reset. I used one tablespoon of Percarbonate and boiling water, left it to steep overnight outside, and then gave it a soft simmer over a towel and trivet in a pot of filtered water. It’s now clean as a whistle, and I’ll need to use it with a cheaper oolong first to recalibrate. I was a little concerned that dripping liquid would streak outside body but thankfully after simmering in filtered water it did not do that.
Cleaning: Awakening & Resetting Unglazed Ceramics / Yixing
I found it is not necessary to wait longer than the foam to dissipate for the Sodium Percarb to do its magic. Once the bubbles are gone I brush a bit with an old toothbrush and then rinse until not slippery anymore. Usually enough, in rare cases an extra round if it was really, really dirty.
