Diapers are just the beginning

The answer is … well maybe, but weight is not the deciding factor in absorbency when the diapers are the same size. It’s really all about the pores.

Your four year old has spilled their drink all over the table and it’s dripping onto the carpet. What do you reach for - the one pound rock or the 4 ounce sponge? The sponge will do a better job even though it weighs less because it has lots of places to absorb liquid - the pores.

The raw cotton fiber is not very absorbent in its natural state. Cotton fiber grows in a boll; each fiber is produced from an individual seed (about 5,000 altogether) in the base. The fiber starts out as a projecting hollow sheath and each night a new layer of cellulose is laid down on the inside of the sheath until about thirty layers are built up. At this point the fiber is like a solid cylindrical rod having a central canal pointing to the tip consisting entirely of cellulose. When the boll bursts and exposes these fibers to sun and air they dry up and collapse, becoming flatter and ribbon like with alternating left and right spiral twist every two or three turns. This is cotton fiber in its original state.

In 1851 John Mercer showed how to apply chemicals to the cotton fiber and cause the fiber to swell and straighten out. No one paid much attention to the process until 1890 when Horace Lowe showed how to use Mercers process to give the cotton fiber what it had lacked – luster and increased tensile strength.

What we get out of this as cloth diaper users is increased absorbency. Without using a mercerizing treatment the cotton fiber would not be absorbent and we would all be using hemp or flax. Hemp and flax are absorbent as well, but cotton is more economical for the US consumer.Absorbency can be increased in a cotton fiber by how it is treated before being woven into fabric and how much it is twisted – flatter fibers absorbing more.

A cross section of dry cotton fiber looks somewhat like a hollow bean. The walls of the fiber contain microscopic internal pores that open and cause the fiber to swell to almost round when wet. It has to have room to do that, so a diaper that is woven to tightly would not absorb as much.

So a higher weight diaper may absorb more if it has flatter fibers (most cotton in diapers is mercerized) and more pores to absorb the moisture. But weight alone does not determine the absorbency of the diaper.Now obviously a diaper that is quite a bit bigger than another will absorb more. But that small difference in weight between the same sized diapers will not tell you which one will absorb more. A heavier diaper may even absorb less if the cotton fibers contain more cellulose than pores to absorb.

Just as an aside most polyester or nylon fibers are man made and extruded from a liquid state through something that looks like a giant showerhead. The fibers are uniform in diameter and are more stable when washed and dried. The fibers of polyester and nylon do not absorb moisture. When they are combined with cotton, they can add stability (no major shrinking) to the diaper. An exception is cloth diapering’s terry weave micro fiber. Micro fiber is a generic term for any thread thinner than a human hair and can be woven for many different uses.

When fluffed up into a nice terry weave, micro fiber can be much lighter than a cotton prefold of the same size, yet absorb much more with it’s uniform man made pores.