What makes materials absorbent

Absorbent materials can be a problem. For example you do not want to be caught in a shower of rain when you are wearing absorbent materials. They will hold on to the water, making you feel wet and cold. Bricks absorb a little water. Those at the bottom of a wall absorb water from the ground. If this water moved up the wall and into the building it could cause damp walls. The water is stopped by placing a non-absorbent material between layers of bricks near the bottom of the wall. You may see this material as a black line in the cement low down in a wall.

In contrast, synthetic fibers like polyester don't break the surface tension, so they don't absorb water the same way. New man-made fabrics combine materials to create much more absorbent fabrics. A composite fabric marketed under the brand name Zorb combines several materials including tangled cellulose fibers and poly microfibers, though the exact combination is a trade secret.

According to the Cloth Diaper Testing site, the material performed best in tests of absorbency and ability to prevent leaks when compressed. The proprietary manufacturing process makes it more absorbent than any one of its constituent components alone, but because it isn't woven it must be sandwiched between layers of some woven fabric.

Cotton is plant fiber which, after processing, is 99 percent cellulose. As Cotton Incorporated describes it, the structure of the cellulose forms microscopic chains. Water is absorbed into the cellulose through capillary action, which is the absorption and movement of moisture between and among fibers. By "wicking" through capillary action, each fiber acts like a sponge to hold water. Individual fibers are spun together into threads.

A paper towel includes more material, so it has a greater ability to pick up spills and dry hands or counters than a normal piece of paper. Towels and cloth are absorbent because they incorporate absorbent material. Cotton and fibrous materials have a molecular structure that offers a multitude of spaces that attract liquids. Synthetic materials are not as absorbent due to their materials, but many sportswear companies sell "wicking" materials that absorb similarly to paper — by distributing the liquid throughout the cloth.

Hard materials are not as absorbent as cloth or paper, and they vary dramatically in their ability to take in liquids. Wood and natural materials are more absorbent than synthetic materials and metals. Metals generally do not absorb liquids to any visible extent. Wood draws in liquids through its vascular interior structure. Most household items have a coating of a special layer of paint or material that either prevents the material from absorbing liquids or prevents rust.