Carding is a mechanical process that breaks up locks and unorganized clumps of fibre and then aligns the individual fibres so that they are more or less parallel with each other. These ordered fibres can then be passed on to other processes that are specific to the desired end use of the fibre: batting, felt, woollen or worsted yarn, etc. Carding can also be used to create blends of different fibres or different colours. When blending, the carding process combines the different fibres into a homogeneous mix. Commercial cards also have rollers and systems designed to remove some vegetable matter contaminants from the wool.
Common to all carders is card cloth. Card cloth is made from a sturdy rubber backing in which closely-spaced wire pins are embedded. The shape, length, diameter, and spacing of these wire pins is dictated by the card designer and the particular requirements of the application where the card cloth will be used.
Fibre is carded by hand or by several types of machine. and was often done by females.
Hand cards are typically square or rectangular paddles manufactured in a variety of sizes from 2x2 inches to 4x8 inches. The working face of each paddle can be flat or cylindrically curved and wears the card cloth. Small cards, called flick cards, are used to flick the ends of a lock of fibre, or to tease out some strands for spinning off.
A pair of cards is used to brush the wool between them until the fibres are more or less aligned in the same direction. The aligned fibre is then peeled from the card as a rolag. Carding is an activity normally done outside or over a drop cloth, depending on the wool's cleanliness. If the wool contains a lot of vegetable matter, much of it will fall out during the carding process, which is the reason for a drop cloth. If the carding is being done to mix two pre-carded fibres, a drop cloth is not generally necessary.
To card, the person carding sits with a card in each hand. The card in the non-dominant hand (left for most people) rests on a leg. A small amount of fibre placed on this card and the other card pulled through the fibre. The moving card separates, straightens, and aligns the fibres. Vegetable matter falls out as the fibres are aligned. Catching too many fibres makes it hard to pull the cards apart. This step, repeated many times, transfers small amounts of the wool to the moving card. Once all the wool has been transferred, the cards are swapped hand-for-hand and the process repeated until all of the fibre is sufficiently aligned and satisfactorily free of debris at which time a rolag is peeled from the card.
The simplest machine carder is the drum carder. Most drum carders are hand-cranked but some are powered by electric motor. These machines generally have two rollers, or drums, covered with card clothing. The licker-in, or smaller roller meters fibre from the infeed tray onto the larger storage drum. The two rollers are connected to each other by a belt- or chain-drive so that the their relative speeds cause the storage drum to gently pull fibres from the licker-in. This pulling straightens the fibres and lays them between the wire pins of the storage drum's card cloth. Fibre is added until the storage drum's card cloth is full. A gap in the card cloth facilitates removal of the batt when the card cloth is full.
Some drum carders have a soft-bristled brush attachment that presses the fibre into the storage drum. This attachment serves to condense the fibres already in the card cloth and adds a small amount of additional straightening to the condensed fibre.