A brief history
The cotton plant is a plant that grows in tropical and subtropical climates. It has large yellow, white or red flowers, in which a capsule or “cotton boll” forms after the petals have fallen off. The cotton plant was cultivated many centuries ago in India. From there, it spread to China, Africa, the Middle East and at last to Europe as well, where cotton fabrics became very popular at the end of the seventeenth century. However ancient and mediaeval Europeans were also familiar with cotton plants, described as “trees of wool” in written sources. Cotton became the most widespread textile material in the nineteenth centrury, although it was overtaken at the end of the twentieth century by synthetic materials.
How are cotton fibres harvested?
Cotton fibres are ready to be harvested when the cotton boll splits open from the pressure of the packed fibres inside. In the past, the bolls were picked by hand and large numbers of people worked in the cotton fields. In the United States, many cotton pickers were slaves until the nineteenth century. An ever-increasing demand for cotton led to the need for mechanical harvesters and the invention of the cotton picker. After picking, the cotton is driven through a “gin”, where the fibre or lint is separated from the seed. Once the seeds have been removed, the cotton fibres are wrapped tightly in bales weighing about 250 kg, ready to be transported to the spinning mill for further processing.
In the spinning mill
The spinning mill is the first stop in cotton processing, where raw cotton is transformed into thread. In the past, spinning mills were usually multi-storeyed buildings with huge windows to provide natural light. Cast-iron columns supporting iron cross-beams were installed in the factories as fireproof elements to protect the buildings from collapse during a fire. The columns are typical architectural elements in buildings of this kind. Besides spinning machines, the factories also had storage facilities, preparatorion areas and reeling machines. Machines were crammed in next to each other and were usually powered by water wheels or steam engines. Working conditions were very unhealthy in the mills. The stress, dust, heat, and noise made such places extremely dangerous for the people who worked there.
Cotton cleaning, opening and forming
Cotton fibres are processed in the cotton spinning mill on a wide variety of machines. When the cotton bales arrive, they are opened, cleaned and formed by numerous cleaning and forming machines such as bale breaker (above), opener and lapping machine (right) with automatic feeder (below).
Waste
Machines also produce waste. Tufts of cotton, pieces of cotton lap and fibres are pulled apart in the waste opener and are then fed back into the opening installation again. In spinning mill, it is imperative to produce as little waste as possible.
Carding machine
The cotton lap produced by the spreader is a flat sheet made up of small clumps of cotton containing impurities, which cannot be removed until the clumps have been completely disentangled. The carding machine is used to disentangle the tufts.
The cotton lap is fed between two carding rollers with slats with small hooks facing each other. At the same time, the fibre mass is refined or drawn for the first time. The cotton leaves the carding machine as a fleece. This is turned into a sliver, a loose strand which is still irregular.
Draw Frame
The slivers produced by the carding machine are worked into equal thicknesses on the draw frame. In this process, six slivers are drawn together into a single sliver two, three or four times. The new sliver has a very regular thickness, with the fibres lying parallel to each other. The cotton fibres are now ready to be spun.This is done in three phases.
The first phase: pre-spinning on a coarse spinning frame
The cotton is first “pre-spun” on a coarse spinning frame or coarse bobbin frame. This machine turns the sliver into a wick, which is wound onto bobbins. To prevent the parallel fibres from slipping, the wick is given a slight twist.
The second phase: pre - spinning on an intermediate bobbin frame
The wick produced by the coarse spinning frame is not yet fine to be spun. That is why the cotton is “pre-spun” for a second time on the intermediate bobbin frame. This produces a wick that is sufficiently fine and regular for definitive spinning.
The third phase: spinning on a ring-spinning frame
The wick is drawn - and thus refined - one more time on the ring-spinning frame in order to obtain yarns of the desired thickness. At the same time, the wick is twisted in order to prevent slipping. The thread obtained in this way is called the single yarn.
To make single yarn even stronger, two or more single yarns can be twisted. This is done on the doubling machine. The result is twisted yarn or twine.
Laboratory
The market value of cotton is determined by the quality of the fibre. Quality varies considerably depending on the geographical origins of the cotton. Before fibres of different varieties are blended and spun into yarn, their properties are examined in a textile-testing laboratory. The properities examined include the moisture content, colour and purity of the cotton, as well as the elasticity of the yarn, yarn count, yarn twist and yarn strength.
What else happens with the final yarn?
The final yarns or threads are further processed on weaving preparatory machines. The thread obtained is used in weaving mills to produce fabrics.
The spinning process described here not only used to process cotton, but also other textile materials such as flax and wool, with certain differences in the machinery used.
Curator—Lenka Barišová and MIAT
