Welcome to our series of articles on the denim manufacturing process. In a series of posts, we will cover all the processes involved in denim fabric production including cleaning cotton fibers, blending, spinning, warping, dyeing, beaming, sizing, weaving, finishing, and packaging. From cotton fiber to the final product you can buy at ZEVA DENIM.
In this article, we mainly talk about the first production process of denim fabric: cotton fibers collection and cleaning!
So let’s talk about
- Where to go for cotton harvest?
- How to clean cotton fibers?
- How to grade the quality of the cotton?
- What’s recycled cotton?
Let’s start now!
Where to Go for Cotton Harvest?
Cotton is one of the most important ingredients for making denim fabrics, so the quality of cotton plays a key role in denim fabrics.
To understand the good and bad factors of denim fabrics, it is necessary to know the types of cotton and which cotton is better produced in which country in advance. Why we need to understand this because it is convenient for us to purchase cotton to make denim fabrics that meet our requirements.
The types of cotton currently available in the market are Upland(Gossypium hirsutum), Egyptian(Gossypium barbadense), Indian(Gossypium arboreum), and Levantine(Gossypium herbaceum).
- Upland Cotton (Gossypium hirsutum)
Upland cotton (Gossypium hirsutum) is the most common type of cotton because it is high yielding and easy to grow. It accounts for 90% of the world’s cotton production.
For upland cotton, the common origin countries are America, Mexico, the Caribbean, and southern Florida.
- Egyptian Cotton (Gossypium barbadense)
Egyptian cotton (Gossypium barbadense) is known as extra-long staple cotton, meaning longer and silkier than most types of cotton. It is characterized by softness, delicateness, and durability. But it is more difficult to produce in large quantities than upland cotton, so it accounts for only 8 percent of world production.
Gossypium barbadense, although it is often called Egyptian cotton, has its origin in South America, such as Brazil and other countries.
- IndianCotton(Gossypium arboreum)
Indian cotton(Gossypium arboreum), commonly known as tree cotton. It can be spun into a single thread and maintain its tensile strength at a higher count than any other cotton variety. Indian cotton is a type of cotton native to India, Pakistan, and Bangladesh.
- LevantineCotton(Gossypium herbaceum)
Levantine cotton(Gossypium herbaceum), is commonly known as Grass cotton. It is cotton extracted from cotton bushes that grow wild in semi-arid regions of sub-Saharan Africa and the Arabian Peninsula.
- Xinjiang Cotton
Xinjiang cotton is called Xinjiang long-staple cotton. The main characteristics of Xinjiang cotton are long cashmere, good quality, and high yield.
Due to the different soil and climatic conditions in Xinjiang, China, it can achieve more than 18 hours of light at most. So Xinjiang is especially suitable for growing cotton! Xinjiang produces more than 20 percent of the world’s cotton.
How to Clean Cotton Fibers?
- Why Need to CleanCotton
After the cotton plants are planted, it takes about two months for each cotton plant to develop flower buds. After about three weeks, the flowers open. Wait for the petals to wilt and fall off, leaving behind green pods called “cotton bolls”. Cotton fibers grow in bolls, and as the fibers grow and swell, the bolls mature and open, eventually forming fluffy clumps of cotton.
These little cotton balls on plants can be picked by hand or machine. However, some leaves and branches may be adulterated during the picking process, so the cotton needs to be washed deeper.
- The Process of Cleaning Cotton
First of all, after the cotton is picked, it goes through the ginning process. The collected raw cotton fibers are fed into the cotton gin. This is a mechanical cleaning process where the machine separates other impurities such as leaves and twigs from the raw cotton fiber itself. Finally, it is dried and compressed into bales called lint.
Typically, about 33 percent of a harvested crop ends up as usable cotton. But don’t worry, the rest of the cotton plant isn’t wasted. The seeds are pressed into cooking oil, the husks and meal are made into animal feed, and the stems are used to make paper.
How to Grade the Quality of the Cotton?
After the cotton has been cleaned of excess impurities, it is formed into bales. So here comes the grade of cotton. Samples are taken from bales and the cotton fibers are graded by experts.
- How Is Cotton Graded?
The comprehensive grades are distinguished from the six major combinations of Color grade, Staple, Micronaire, Strength, Length Uniformity Index, and Impurities. We have explained this in detail in a previous article, if you want to know more, please click How to grade the quality of the cotton.
What’s Recycled Cotton?
In fact, in our denim industry, there is another source of cotton, which is old cotton or recycled cotton.
- What Is Recycled Cotton?
Recycled cotton is usually recycled from yarn and fabric by-product waste, and some unused fabrics are decomposed and recycled.
The largest source of recycled cotton is produced from pre-consumer waste, such as cutting waste.
The quality of recycled cotton is good or bad, but it depends on whether the processing process of recycled cotton is fine or not. Cotton that has been treated is as white as new cotton and has good coloring, while cotton that has not been treated will appear yellow and have bad color.
After the cleaning cotton process is complete, the next stage is blending. so we’ll cover that in the next article, which you can read by clicking How Denim Is Made: Blending Synthetic Fibers With Denim.
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