Different types of fibers react to moisture differently, and the key to a good project is to choose the correct fiber for the item you are knitting. Below are the three most common types of fibers.
Cotton: Cotton wants to be wet, it wants to pull in those water molecules and love them, and hold them, and keep them as long as it can. Cotton is ideal for absorbency and items that move around water like towels, dish rags and bath mats. However, once saturated it will take a long time to dry.
Acrylic: Acrylic doesn’t want to be wet, so it starts out by shedding the water. But after a little bit it throws a temper tantrum and says “Fine then! IF you want me to be wet I WILL BE!” and then grabs onto the water and holds on. It doesn’t make good dish rags or towels and is an OK choice for winter wear such as mittens and hats. This is especially true if wash-ability and fiber allergies are a factor, but once wet it won’t keep you warm. It drys faster than cotton.
Wool: Wool hates to be wet, it can shed water droplets without absorbing them. It does everything it can to stay dry and it will take any excuse to become dry again. It will shed water because of gravity and items that have gone through the spin cycle of a washing machine are almost dry to the touch. It also still keeps you warm while wet which makes it an ideal cold weather garment.