Doll hair can be made of a various natural or synthetic material (fibers). Doll fiber types differ with respect to their maximum length (staple length), width (diameter measured in microns), available colors, shape, and, off course, availability and cost. Their production also impacts the environment in diverse ways.
Natural fibers are obtained from animals (e.g. human hair, wool, mohair, alpaca, silk) or plants (e.g. flax, bamboo, soy). Synthetic fibers are made of polymers (e.g. saran, nylon, kanekalon) or cellulose (e.g. viscose, lyocell, acetate). The basic ingredient of cellulose fibers is wood, but they are processed chemically to such an extent that the "synthetic" adjective is warrented.
There is a great variety of natural fibers, with regard to their texture, color, length, and shape. Most of them can be dyed, and some can be felted. On the downside, while the uniqueness and natural variety benefits some hairdos, for other projects - which require greater uniformity - they may become a nuisance. Some natural fibers are too fragile for combing, washing, or styling. Also, there are people who are allergic to lanolin, and those with sensitive skin will shudder at the thought of working with a rough material. As regards ecology, natural fibers can often be bought from small local producers, they are 100% biodegradable, and they can be recycled - but only as long as care is taken for the animals or plants which provide the fibers. Monocropping and overharvesting plants harms the environment, and animal fiber donors may suffer (mulesing, shearing before a temperature drop, shearing itself) or even die (silkworms, Tibetan lambs, often other animals) in the process.
Synthetic fibers can be made very long, in any color, consistently the same if needed, and may have interesting finishes (e.g. gloss or brocade effects). As regards styling, depending on the quality of the material, they may fall anywhere between frizzing at the mere touch to being very durable and resistant to combing and curling. However, as a rule, they melt easily in higher temperature; for that reason, they should be kept away from heat, sparks, and open flame. Synthetic fibers rarely cause allergies, and no animals are stressed in the production process. Obviously, though, their production depletes natural resources, and most synthetic fibers are not biodegradable or recyclable.
To be continued : ) I will try to post photos and detailed fiber characteristics in the following posts.