Fibres

Different fibres used in nappy-making have different properties. Here's a brief explanation of these:

Hemp

Though hemp is often joked about ("hey, let's smoke our clothes, man"), it is only a distant cousin to marijuana. It contains far less THC, and will not get you high. On the other hand, it makes great clothes and nappies. Hemp fibre is soft and duraable, and is reputed to have antimicrobial properties. As the hemp plant requires no pesticides or fungicides, and relatively little water for growing, it also has a very low environmental impact. Hemp in nappies usually comes in the form of hemp/cotton blend knit terry or fleece, or jersey (tshirt material), though it can also be found in woven fabrics, in the form of slings, sheets, or button shirts. Hemp denim and corduroy are also popular for making clothing.

Hemp is more absorbant than cotton, making it popular for overnight nappies, or nappies for heavy wetters. It does absorb more slowly than cotton though, so is best teamed with other, faster absorbing fibres.

Bamboo

Bamboo is the new wonder fibre - made by pulping the bamboo fibres, by similar method to the production of Rayon, bamboo is luxuriously soft and silky, and feels very cool to touch. As Bamboo is a grass, and grows very quickly, this crop takes almost no maintanance or resources, so its environmental impact during the growing stage is minimal. A single plant can produce a huge harvest, without having to be replanted or replenished. Even better, the bamboo used to produce fibre for fabric making is not the same species as is used for food by pandas, so this endangered species is not put at risk by the use of this fibre.

Bamboo seems to absorb quickly, and hold moisture well, but hasn't been in use long enough to get some good data back as to its ranking in the absorbancy arena.

Cotton

Cotton is the most predominately used, and most readily available natural fibre. Its crops tend to be rather high impact, taking more water than other fibre crops, and on most farms, grown with the use of pesticides and fungicides. In recent years, there has been an increased tendency towards organic farming, which is farming without the use of chemicals, or excessive irrigation. Organic cotton has a far lower environmental impact than commercially grown cotton, and feels softer too.

Cotton is about middle-of-the-range as far as absorbance goes. It is quicker at sucking up the moisture than hemp, but doesn't hold quite as much. Cotton is great to team with hemp, particularly for toddlers or heavy wetters.

Wool

Wool is another wonder fibre - it is warm in winter (but not hot), and cool in summer (but not cold, even when wet). It absorbs, and at the same time provides a water "barrier" over a nappy to keep clothes dry. When teamed with lanolin (the "grease", or sebacious oils, of a sheep), it provides water-resistance, and prevents smells from urine. Used with an adequate nappy, wool makes a great cover, that keeps baby at a comfortable temperature, as it allows evaporation, without making clothing or bedding damp.

With lanolin, wool absorbs very slowly, as the lanolin provides waterproofing. Wool can absorb up to 30% of its weight without feeling damp, which makes it an excellent second line of defense for a wet nappy. It can also be used unlanolised as a booster.

Man-made Fibres and Fabrics

Polyester is another commonly used fibre in nappy making - as it is hydrophobic (water "hating"), it can be used both as a stay-dry layer inside a nappy in the form of suedecloth or micro fleece or polar fleece, and as a cover, in the form of double-layered or thick polar fleece. Polar fleece covers do allow for evaporation, but do get hotter than wool covers, as they don't absorb as much moisture. Polar fleece tends to be prone to "build-up" from detergents, which can cause smells and rashes.