Denim Basics

Origins of “Jeans” & “Denim”

Where does the word “jeans” come from?

Jeans date back to 1567 with the introduction of the word “genoese” or “genes” to describe the tough twill trousers worn by merchant sailors from the Italian coastal city of Genoa.

Where does the word “denim” come from?

Denim dates back to the 17th century. Created in Nîmes, France, serge de Nîmes was a cotton twill cloth made of wool and silk. It later became known simply as “denim.”

Levi Strauss & Co.

Denim in Fashion

Characteristics of Denim

The basic denim jean gets its unique character from its yarn, indigo dyestuff, weaving and design, and washes and technical finishes.

Like other fabrics, denim can be dyed, washed down, chemically finished, or mechanically finished.

Chemical finishes can include the application of such substances as DP or durable press, softeners, stain repellents, water repellents, and others.

Mechanical finishing can include brushing, sanding, laser etching, color discharge, and many other novel effects.

These effects are made possible by the special character of denim yarns, the special character of indigo dyed yarns, specialized garment processing machinery, denim garment washing and finishing processes, denim garment overdyeing, and denim garment functional finishing.

Denim Yarn

The final look and feel of a denim garment depend in large part on its yarn. Yarn can range from soft to firm, even to uneven, weak to strong. The yarn’s twist direction and level of twist also impact the final effect of garment finishing as does the choice of ring or open-end spun yarn. In recent years, advances in the production of effect yarns, such as slub, accent, and stretch yarns have also played a part in developing new looks. With denim, yarn evenness is important. Even yarns provide a smooth surface that washes down or abrades to a uniform shade. Uneven yarns that vary in thickness result in great variations in shade. In fact with some abrasion finishing processes, thick areas can be abraded down to the white yarn core of the indigo dyes while the thin areas might be hardly abraded at all.

Yarn twist has a similar impact on color and abrasion results. Low twist yarns are softer and tend to wash down or abrade more rapidly than higher twist yarns. Yarn twist also affects fabric hand, stiffness, strength, skew, cover, drape, appearance, and other characteristics. Another yarn characteristic that impacts finishing is size including the mixture of yarn sizes in a single fabric. Varying yarn sizes will affect finishing in a way similar to that of slub yarns. Slub yarns are yarns spun to have long and thick effects in them with subs in either the warp, filling, or both. Open-end and ring-spun yarns can both obtain slub effects.

Indigo Dye

Indigo dye is one of the most important factors affecting the look of denim. When indigo dyes are used, it gives the denim fabric a unique ability to fade in color after repeated laundering.

During the 1980s, there was a designer jean craze with many styling variants. This phase ended in the 1990s when Levi Strauss & Company created the “Back to Basics” slogan. This began the revival of the ringspun denim but by the mid-90s, the designer jean craze had resurfaced with many companies producing their own brands. Now, advances in finishing techniques especially garment processes and fabric technology have created a high-tech denim jeans market.

Indigo dye yields a deep, bright shade of blue but with a low affinity for cotton, and as a result, it can be easily washed down in mill processing. Even the most state-of-the-art synthetic versions of indigo have an improved cotton affinity. Ring-dyed cotton is the key to many current denim garment finishes. Ring-dyed or white core cotton refers to yarn that is dyed with indigo in such a way as to keep the core of the yarn white. The white core is clearly visible. Without this ring-dyed effect, many of the most popular denim garment looks would not be possible but with proper cloth construction, dyeing, garment manufacturing, and finishing techniques, denim continues to take on fresh new looks.

Overview of Denim Manufacturing

Warp yarns used in indigo denim fabrics must go through numerous processing steps before they are ready to be woven. These processing steps are unique to indigo fabric manufacturing. Most often the warp yarns are indigo dyed on a system referred to as a long-chain or rope range. For this system, multiple ends of yarn are formed into a rope or ball warp and then continuously dyed.

After dyeing, the dyed ball warp is rebeamed into individual yarns evenly spaced onto beams called section beams. These beams are then slashed and then woven. If the warp yarns are to be slasher or sheet dyed, then the yarns will be warped onto section beams and indigo dyed. In most cases, the yarns will also be slashed or sized in the same process. The yarn is then woven. If the warp yarns are to be beam dyed, then the yarns are warped onto perforated dye beams for dyeing instead of being formed into ropes.

After beam dyeing, the dyed yarn is then slashed and woven. If it is chosen to have natural warp yarns, then prior to weaving the yarns will be warped onto section beams then slashed and woven. The fabric is then processed in a normal manner. This would include desizing, preparation, dyeing (if desired), and finishing. Unlike the warp yarn, mot filling yarn is put onto yarn packages and delivered directly to the weaving machine where it is inserted into the fabric without any wet processing but sometimes dyed filling yarns are used to achieve a different looking denim.

Denim Construction, Weaves, & Weights

The weights of the finished fabrics vary between 3.5 and 16.5 ounces per square yard. The fabrics weighing 3.5 to 8 ounces per square yard are typically used to manufacture blouses, tops, and shirts. Trousers, jeans, and jackets tend to use heavier weight denim fabric ranging between 8 and 16.5 ounces per square yard.

Numerical notations for different denim designs, such as 3 X 1 twill, denote what each warp yarn is doing relative to the filling yarns interlacing with it.

In this example, look at the end marked number 1. This warp yarn is going over picks 1, 2, and 3 and then under pick number 4. We see that with the end marked number 2, the same sequence is being repeated but advanced up one pick. This means that the warp yarn is under pick number 1 and goes over picks number 2, 3, and 4. This upward advancing sequence continues, thus giving the characteristic twill line. In this case, the twill line would be rising from the lower left to the upper right and the fabric would be classified as a 3 X 1 right-hand twill weave. If the twill line is made to rise to the left, then the design is a left-hand twill.

Non-Conventional Denim Fabrics

Non-conventional denim fabrics include: