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How are Jeans made?

A Chemistry Project By Wendy

Wendy Cai

on 22 December 2010

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Transcript of How are Jeans made?

How are jeans made?
Let's find out! By: Wendy Cai It starts with cotton... ...which is usually picked in places such as China, United States, and India. In fact, these are the top three producers of cotton! Cotton is usually gathered by a large machine called a mechanical cotton picker. Here’s a fun fact, in just five minutes, it can collect over 50 kilograms of cotton! Before the cotton can be used, it must go through a cleaning and picking machine which will separate the cotton from the seeds, break it into smaller pieces and remove the trash. The carding processes combs and untangles fibres to form a consistent cotton slivers. Gathering Sorting Carding Spinning 4. At a rate of 120 thousand revolutions per minute, the cotton is pulled and stretched to form strong thread. Just twenty grams of fibre can produce an entire kilometre of fine yarn. At a rate of 120 thousand revolutions per minute, the cotton is pulled and stretched to form strong thread. Just twenty grams of fibre can produce an entire kilometre of fine yarn. Dying Now that the cotton can be used, it needs to be dyed. But not indigo, but rather leucoindigo (yellow). Why yellow?! Indigo blue dye is not soluble in water! It must first undergo a reduction reaction. reduction – oxidation reaction that will donate an electron and therefore become oxidized Recap:
reduction – oxidation reaction in which the compound will gain an electron The threads of cotton must be mixed with a reducing agent to become oxidized The reducing agent is sodium hydrosulfite, which will turn the fibre yellow. And that's why it is yellow! Unlike indigo, leucoindigo is soluble in water...can you guess why? Because of the charges on the oxygens, leucoindigo is polar, and therefore can dissolve in water, which is also polar. Once it comes in contact with oxygen, it becomes indigo. We know it is non-soluble because the charges are gone. Another fun fact: since the bonds between the jeans and the cotton are not strong, jeans tend to fade, which gives it its characteristic shades. The indigo thread is treated with corn starch to add stiffness. Threading Since jeans usually have a mixture of blue and white colours, the indigo thread is mixed with white thread at a 3:1 ratio in a loom. Another Fun Fact: An average loom can produce up to 3000 meters of denim per week. Cutting 100 sheets of long denim are piled 100 sheets deep and tailored into shapes programmed by a computer to waste as little as possible, usually at 7%. Sewing The parts of the jeans are then sewn together separately by different people all specializing in one step. Division of labour, if you are an economist. One pair of jeans usually takes around 15 minutes to sew, and if you passed grade 3 math, thats 4 pairs per hour. Grab a calculator if you must (Taffy). What Now? It's time to have fun with jeans!
After all, no one has jeans like these anymore: You can say that hydrophilic molecules 'like' hydrophilic molecules because they both have a charge. We say that indigo is hydrophobic because it does not dissolve in water. Since it does not have charges, it is not polar, unlike water and leucoindigo Enzymes, which are like biological catalysts, are used to physically eat away the cellulose in cotton. Remember from chemistry: cellulose is a carbohydrate found in plants! When the denim is washed in a cellulose enzyme bath, the indigo is removed along with the fibre. When the desired colour has been achieved, heating the water stops the enzymes from reacting. By heating the water, the enzymes will denature. Their tertiary form changes, and they no longer can perform their function. Cool huh? Enzyme Wash Fade created by Enzyme Wash Environmental Impact:
This process is more environmentally-friendly than stone washing because strip-mined pumice stones are not used. Chemical Wash Mainly through the use of strong base additives, such as NaOH, to achieve the purpose of faded, washed clothes. This gives jeans its characteristic 'worn-out' and 'I've had these forever, don't mind the price-tag I forgot to cut' look. Acid Wash The jeans are washed with chlorine-soaked pumice stones. Afterwards, they are treated with an 'antichlor' such as sodium bisulfate to remove the chlorine content in the jeans. This process strips off colour from the top layers, giving a faded look. And That's How Jeans Are Made! Hope you enjoyed this!
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