STEP 2
fabric production
A NOTE ON MILLS' ELECTRICITY:
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Fabric production is the step in the life cycle of a garment that has the highest impact. According to Life Cycle Assessment experts Ecochain, almost 10% of the impact of the apparel industry occurs by producing the fabric, which is made in fabric mills. These are extremely large factories with gigantic machinery which often runs 24 hours, which is why the sustainability of spinning and weaving is very connected to the type of energy that is used.
Need help finding a supplier or getting connected directly at the farm level? Contact Simply Suzette here.
CLEAN ENERGY
Renewable energy sources are the best option. Hydro and wind power require large scale installation, which should be made available to mills by energy companies or government help. Manufacturers have started installing solar panels on their roofs that fit very well in the countries that produce most of the world’s denim: India, Egypt, Pakistan, Turkey. You can find a great comparison of different energy sources here, and our article on Solutions for Fossil Free Energy in Fashion.
SPINNING
Fibers are cleaned of any impurities like sticks and leaves, this means separating the cotton lint (the white fluff, a mass of unicellular hairs that grow attached to the cotton seed). The fibers are then spun into yarns that are woven into fabrics, and this is where you would also add other fibers such as Tencel, Refibra, or bio stretch.
A lot of cotton can get lost during this stage, but most mills have vacuum-like machines that will suck up all the lost cotton during the process and recycle it back into their feedstock. Cotton is like gold, it cannot be wasted!
Ring Spun vs. Open End Spinning:
+ Ring-spun yarn is made by twisting the cotton strands to make a very fine, strong, soft rope of cotton fibers. Ring-spun yarn is more durable than open end yarn and generally more expensive.
+ Open-end spinning, on the other hand, is a system of spinning where the yarn is twisted by rotating at the hap or break in the flow (the fibers wrap around the yarn vs spinning one long piece of yarn).
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INDIGO
In theory, this is just one dye, but the outcome is much more than that: it can be pale, dark, bleached etc. This is possible because it’s not a perfect dye, given its values for color fastness and bleaching resistance that bring its imperfections.
In denim, we have two main types of dyes: indigo and sulfur. However, indigo and sulfur have troubles sticking to the fibers on their own. Indigo requires multiple applications to develop the color, about 6 - 8 dips on top of exposing it to oxygen and stabilizing it before dipping it again.
Indigo can be either natural or man-made, but the molecule is the same, and it has to be solubilized with sodium hydroxide (caustic soda) and reduced with sodium hydrosulfite (hydro), regardless of whether it was sourced from the Indigofera tinctoria plant or from aniline and other chemicals. “Aniline free”, which you might see in sustainability communication from brands, refers to detectable amounts of residual aniline that can be found in the indigo dye paste, however the indigo dye is still made from aniline.
Although there isn’t a difference in the way it is applied, the production of indigo is very different. Making synthetic indigo is a complicated chemical process with high health and safety risks, which should be done in extremely careful facilities. The chemicals are derived from petroleum, and we all know the destructive effects that the extraction of it has on the planet.
Chemicals are one of the main components of our clothes, but have gotten a terrible rap over the years. When chemicals are used properly and safely, they can have some benefits. However, heavy use of chemicals causes massive freshwater and ocean pollution, as well as soil degradation, which poses a great threat to global food security and biodiversity.
Unfortunately, natural indigo takes more time and land to produce, and it cannot meet global demand.
There is a great online webinar by the Transformers Foundation: “THE TRUTH ABOUT INDIGO” - The Truth Series: Season 2 Ep.4. which covers the technical side of indigo and answers a lot of the questions you might have on it. The experts tell us that if you look back to ancient times, Samurais used it to heal their wounds, as a flame retardant, for its healing properties, and its odor prevention, making it much more than just a color.
DYEING
Most denim fabric, even the ones that are used for your vintage looking light wash pairs, are dyed dark, and then reduced in color, which creates our desired final result. This means that chemicals are used at the dyeing stage and then later on again (jump to ‘washing’ here).
First, the yarn has to be treated with caustic soda and a wetting agent to remove natural oils in the cotton and impurities that cause inconsistencies in the dyeing. Rinsing is crucial for the dye to permeate the yarn.
Then the yarns are dipped into several baths of indigo in a continuous rope dye range. The vat is the indigo bath.
If you wanted to add sulfur to compliment the indigo with a cast of black, you would do so before dipping the yarns in indigo during cleaning or after indigo dyeing to achieve different looks.
After the dye is applied, the yarns are washed to remove any residual indigo. Indigo and sulfur dyes are not colourfast, so they can be easily removed in the laundry, but more on that later.
WEAVING
​To most denim enthusiasts, the difference between a woven and a knit fabric is very clear, and they will also know that denim tends to be a twill woven fabric. But this is not an exclusive club: we want to include everyone! So, what’s a woven VS knit?
A knit fabric is made up of a single yarn, looped continuously to produce a braided look. A woven fabric is generally produced on a loom and made with many threads that will be placed at two specific angles. The two angles will then define your warp and weft directions. Denim is a woven fabric, made of a dyed warp and a bleached or undyed weft. This is why when you turn your jeans inside out, they are a different color!
To set our yarn up for weaving, we need to coat it to ease the friction that occurs during weaving known as a sizing formula. Then we take our dyed yarns for our warp and our undyed natural yarns for the weft!