Secret of Kozo Paper’s Strength

It is no secret that kozo papers are stronger and more durable than most papers in today market. A thin sheet of kozo can punch above its weight class when it comes to the ability to withstand wear and tear. In this post, we will explain why our beloved papers have such properties!

Every paper is made from wood or vegetable fibers that have a property called "self-adhesion." This means that the fibers stick together at the point where they touch. This property was discovered by accident in ancient China and led to the creation and modification of paper.

To understand self-adhesion, it's important to know that vegetable fiber, cellulose, are made from glucose molecules that are connected lengthwise. Cellulose does not dissolve in water, but it does absorb water easily and expand. Once the fiber is soaked in enough water and formed into a sheet, it is then dried, making the fibers stick together. This is called "hydrogenic cohesion." Although each individual cohesion is weak, collectively throughout the sheet, it creates a strong bond and results in a sturdy sheet of paper.

One reason why kozo paper is stronger than wood-based papers like everyday office papers is that the fibers used in kozo paper are longer. Kozo fibers are on average 7 mm long, while wood pulp fibers used in typical papers are only 2 mm long for softwoods and 1 mm long for hardwoods. The ratio of length to width of fibers is also different, with a ratio of 500 for kozo fibers and only 85 and 60 for soft and hard wood pulps, respectively. These properties allow kozo fibers to easily interlock with each other and create a strong sheet of paper when dried.