Fiber orientation and paper properties

Paper properties are affected not only by raw materials and the papermaking method, but also by the alignment of fibers, which is called “fiber orientation.” Here we’ll learn more about this fiber orientation.

In paper made with machines, like that shown in Step 1.15, fibers are aligned in a direction called the fiber orientation (fig. 1). Fiber orientation is stronger in machine-produced paper than in handmade paper.

^{fig. 1. The strong fiber orientation of machine-made paper (From takeopaper.com)}

Let’s experience fiber orientation by tearing paper.

By tearing paper, you can see differences in the strength of fiber orientation. Let’s try tearing and comparing commonplace papers made from different raw materials, like copy paper, paper napkins, and washi.

Tear the paper in two directions:

1. Tear the paper in the vertical direction.
2. Tear the paper in the horizontal direction.

Was there a difference in the ease of tearing?
Was there a difference between tearing in the vertical and horizontal direction?

Paper should have been very easy to tear along the fiber orientation.
It should have been hard to tear across the fiber orientation. This is fiber orientation.

The photo below shows the situation when copy paper is torn (fig. 2).

^{fig. 2. Tearing copy paper}

Paper properties vary like this, depending on the strength of fiber orientation. Of course the difficulty of tearing may also vary due to the type of paper. Fiber form also affects tearing difficulty. For example, washi fibers are long, as shown in Step 2.17, so tearing is more difficult.