Denim Dictionary
The story of Denim
In the beginning there was cotton. And, as you know, cotton is denim's raw material. So what we're going to do now, is guide you through the processes that turn cotton into denim fabric and ultimately into denim clothing.
We start off with the crops that are grown both in the US and in Europe. This is where we find the whitest of cottons, which are eventually picked and packed into large bales. Once the bales are packed and collected, they're sent to the factory for where the industrialization process begins. The cotton bales are taken apart and and people manually go through the picked cotton once again, cleaning it and taking out any impurities such as small branches, shorter fibers etc. Once our cotton is cleaned and sorted, the next step is making the yarn. There are three varieties here, all of which require different handling: Open end Yarn, Slub yarn and Ring Spun.
Open End
Open end, invented in the 1970’s to keep up with large worldwide demand for denim production, is the fastest and cheapest way to make the yarn. About 100 meters (ca 300 ft) is created in no more than one minute. Picture a large washing machine spinning cotton and passing it through a small, narrow tube at the back, under high pressure. You can add endless amounts of cotton and it will just keep adding to the cotton being passed through the tube. Hence the name “Open End”: it can keep going as long as you need. Although very easy and cheap to produce, open end yarn lacks pull-strength, is more colorfast, and lacks character, by its very nature.
Slub yarn
Frequently referred to by us as Open End’s little brother, slub yarn was invented shortly after open end yarn, to try and give life and character back to mass produced yarns. Slub is created very much like Open End, but instead of just passing the cotton through a pipe under constant pressure, the yarn is pulled through at varying speeds and has little holes perforated alongside the pipe, to inject air into the yarn and give it a more inconsistent character.
Again, this yarn does have a more authentic look similar to Ring Spun, but this high quantity production yarn still lacks pull strength and is just as color fast. Nowadays, the Slub yarn is so well evolved that even the biggest and authentic companies in the world are using this instead of Ring spun yarn. 'Who sees the difference?' is their reasoning, conveniently forgetting we are buying history.
Ring Spun
This leaves us with Ring Spun, the most authentic way of making denim. Before the 1970’s Ring Spun was the only way to make yarn, making it the most authentic. Manufacturing and production are more time consuming for this type: 1 minute of processing only creates 20 meters (ca 60 ft) of yarn. Instead of just being thrown into a washing machine-type contraption, ring spun cotton is laid out and the cotton bales are compressed down to a mattress-like thickness and then combed in a constant direction. The 'mattress' is then cut vertically, into long strips. At the end of one of the strips, a thread of the cotton that sticks out and inserted into the contraption, which then starts pulling the material through a ring.
Don't we all remember the story of Rumpelstiltskin and the soon-to-be-queen spinning the golden yarn? Back in the day, ring spun yarn was fabricated the exact same way: a spinning wheel that pulled the thread through the ring at different speeds, as though controlled by man. This is what gave ring spun its irregularity. And every time the yarn hit the ring, it would cause the cotton to bunch up and make little bulges in the cotton. Now even though today it is most costly and more time consuming to make Ring Spun Yarns, it is the most authentic way. Moreover, it has the strongest pull strength, retains the color the best and is inconsistent, so it gives our denim the most character.
Indigo dipping
When our yarn is created, we coil it up to make a rope, much like the ropes we used to have in gym class. You know what we're talking about: the ones that we were ordered to climb to the ceiling but never quite managed to. This rope, thick as a grown man's wrist is then brought to the indigo dipping vats. These days most brands use synthetic indigo (read: a mix of shiploads of chemicals and a little bit of indigo).
There is, however, a positive side to this and that’s that the ropes get a consistent color, day after day, year after year. In other words, if you want to buy a new pair of this variety, you can trust it to have the exact same color and feel. The real, authentic indigo is not used much any more, because the color is not consistent and it takes too long to dye the yarn. Besides, standard indigo will not stick to cotton. A good example is the natural indigo-dyed Momotaro that retails for about EUR 2,000.
So, the yarn ropes are dipped into our vats of indigo. The rope goes into the first vat, and is then pulled out to allow it to oxidize. A process which is then repeated up to 18 times, though usually eight times does the trick. The indigo is not absorbed into the yarn, rather it just coats it. The more we dip, the thicker and darker the coating on the yarn, much like when you paint your house: a couple of layers are required to make sure the walls are well coated. As a final step in this process we might occasionally apply a different shade of indigo, like the greenish kind, to give a green tinge to the yarn. Once the yarn is coated, it's ready for the weaving process.
Rag weave, cross weave and broken twill
Here too, there are varieties to the process: three different kinds of weaving, to be exact: the rag weave, the cross weave and the broken twill. The rag weave, found in most of our denims is the tightest of all weaves and retains its color the longest. You recognize this weave by its slightly diagonal incline when looking at the warp. The cross weave, currently found in some of our denims, is a looser weave, recognizable by a vertical and horizontal yarn pattern. This weave is a more color-consistent weave, which works really well if you are looking to create a faster worn-in look.
The third weave, the broken twill, is not really used these days, but was created to get rid of negative aspects in raw denim jeans. Broken twill can be spotted by its zig zag pattern going up the denim. This weave pulls to the left and to the right so that the jean has a reduced chance of getting twisted leg. Because of advances in denim processing, this weave is no longer required but if you do come across it, it is likely that it was used for reasons of authenticity.
Once the yarn is weaved onto our industrial looms, we are ready for what we like to call “The four S's “ processes: Sanforizing, Skewing, Singeing and Starching.
We start by sanforizing the denim; this is a process that reduces shrinkage of denim by some 20%. This is done by pouring hot steam through our denim at high pressure. Before sanforizing took hold, people had to buy denim a couple of sizes bigger, so that when they washed the denim, it would shrink to its proper size. Today, thanks to sanforizing we can sell length sizes. Once the sanforizing is done, we take the loom to the skewing process. This is done by taking the rolls of denim and passing it through two hot cylinders that spin in opposite directions. This step helps get the twisting of the leg out of the weave and locks the yarn into place.
After all this processing, little bits of fluff and threads are often found sticking out of the denim, so we then subject the yarn to the singeing process: we literally burn the denim to give the denim a clean surface. Finally, we bring the denim to the starching process. This is an important step, as we lay the denim down flat and starch it to make sure it does not move. Since we stack up to 40 layers of denim at a time, on a neat pile before we cut the patterns, it is important that the denim does not move. This way we get the same pattern cut from the top layer of denim all the way down to the bottom.
Once the layers have been placed on top of one another and the patterns are applied to be cut out, most companies use a jigsaw-like device to cut out the denim. A basic 5-pocket denim is created from four main pieces, two for each leg. The legs are then sewn together and pockets, belt loops, buttons and rivets are then added. We now have a finished denim jean, which is usually referred to as 'raw', 'dry' or 'rigid' denim, because it has not been altered, rinsed or washed in any way.
Washes and rinses
Should we want to create a worn-in look, there are a couple of things that can be done to the denim: a simple rinse is one option, which would fade it slightly as well as clean out most of the starch. Alternatively, a pumice stone wash could be applied to batter the denim a little and give it a more rugged worn-in look. Most of the time a pumice stone wash is recognized by the broken and beaten effect on the seams and the cuffs of the jeans. If we wanted to achieve a whiskering or mustache effect, we would bunch up and pin together specific areas of the denim and take a polishing tool to the surface of the denim at high speed, thus removing indigo from the yarn.
Sand blasting can also be applied by way of detailing, but you must be very careful as this entails shooting glass and sand at the denim at high pressure - if not done correctly you could rip right through the denim. Scraping and sanding are similar processes, but their advantage is that while they do the same, they're easier to control the effect with. And finally if you're looking to give the denim a destroyed look you could also go over certain parts of the jeans and manually cut the denim with a razor blade, causing it to fray.
That about covers it all. Contrary to shows like Jackass, we would encourage you to please try all of the above at home, to personalize your jeans any way you like, as long as you don't end up sand-blasting your neighbor, or an unfortunate part of your own anatomy in the process.
Regards,
Rene Strolenberg