Qualities of Kiribako: An Overview of Paulownia

By Ray Suzuki | April 2nd 2024

#factory #science

With an array of unique features, Kiri-bako style boxes have long been used to store some of the most precious items in Japan for over 300 years

It’s almost hard to believe that wood could be fireproof… Kiri (or Paulownia) wood is porous, with a honeycomb structure that carbonizes upon ignition. With a low number of ligins Ligins, are amorphous polymer, and a key wood component. paulownia has a low number of these, therefore generating almost no combustible gas when heating. This combined with its oxygen blocking structure means it successfully protects itself from fire.

Did you know that one type of wood could be 66% lighter than another?
With its air-holding cell structure, the Paulownia tree is significantly lighter than most other hardwoods: at 14 lbs per cubic foot, it is a third of the 44lb Oak’s weight… Therefore it’s more conveniently portable, and carryable as a box, than any other timber.
This means high protection, in a conveniently light materialization: precious objects can be shielded in ways that don’t require the most heavy and cumbersome of materials.

The boxes are anti-corrosive, due to Paulownia’s high tannin count. Tannins are a protective substance within the makeup of trees. Stored in the bark of the tree, tannins are a highly anti-corrosive ingredient. Paulownia contains a larger than average amount of tannin, making our kiri-boxes highly resistant, as well as inhibiting the growth of bacteria in humid environments.

Paulownia timber hardly shrinks: making it even more airtight. Unaffected by any humidity, the boxes protect their insides from external air conditions.

Chowa boxes possess controlled-friction, which is a feeling which you may be familiar with: Apple patented their Air Pocket packaging, their boxes hold a particular air gap, creating friction when opened. The luxury feeling associated with the drama of unboxing an item, has meant less people dispose of their packaging. In Kiribako’s case, it means that, and more: Chowa boxes are air tight, sealing their contents and historically suitable for storing dry food products such as rice and other grains.

Furthermore, kiribako are insect resistant: with paulownia timber containing ingredients that repel bugs, such as paulownin and sesamin. It was for this reason that for centuries these boxes are known for keeping precious kimono and fabrics safe.