Why Do Natural Fibers Absorb?
Hemp and organic cotton both make great diapers. Wool makes great diaper covers. These fibers are beautiful not only in the world of seeing and touching the fabric but in the microscopic world. All images are taken by the author with a Scanning Electron Microscope (SEM).
Microscopically, the surface of cotton fibers is smooth, with a slight kink, which makes it easy to them weave into a strong fabric. In cross-section, cotton fibers are "c" or "u" shaped. Cotton is a natural, cellulosic fiber with excellent properties for diapers: it is soft, absorbent, strong, and machine-washable. Its absorbency comes from the fiber surface (which has a high affinity for water) and the fiber core microstructure (which resembles millions of tiny sponge-like tubes).
This image shows 100% organic cotton at 250x magnification.
Microscopically, hemp fibers have a similar structure to that of cotton, with a smooth outer surface and a sponge-like core. The fibers are flatter in profile than cotton and have a slightly segmented appearance (like bamboo). They also have a natural kink that tends towards a gentle spiral.
Hemp is also a natural, cellulosic fiber—just like cotton. The difference between the two is that hemp possesses all of cotton's beneficial properties to a greater degree. Hemp is three times stronger than cotton, has good abrasion resistance and is washable.
In addition, hemp has some other helpful properties that make it a fine choice for diapers. It is naturally anti-microbial and resistant to mold, mildew, rot and degradation by UV-light. A slight drawback of hemp, compared to cotton, is that it is not as soft (although it does soften with repeated washing, which cotton does not). This drawback is usually ameliorated by producing a blend of hemp with cotton. This combines the best properties of both fibers.
The first image shows 100% hemp at 250x magnification. The second shows 55% hemp/45% cotton at 25x and 250x magnification.
Wool is a natural protein fiber made from the fleece of sheep. The surface of wool fibers consists of an outer layer of overlapping scales, called cuticles. Water droplets run off this layer easily, which is how sheep stay dry. Inside the fiber, the structure resembles that of hemp and cotton.
This structure will absorb up to 30% of its own weight from moisture in the surrounding environment. When boiled, the fibers kink and enmesh, forming a lofty, water-repellent, breathable fabric. It is a good insulator and uniquely combines the three useful properties of water repellence, moisture absorption and breathability.
This image shows 100% wool at 25x and 250x magnification.
by Marc Pehkonen
copyright © 2000 - 2007 Marc Pehkonen. Used by permission.