When you picture a pair of jeans, they may be athletic fit jeans or stretch denim jeans or skinny jeans for guys, but, nine times out of ten, they invariably a form blue jeans. That classic blue color has forever been associated with the pant style since its beginning in the late 1800s.
The blue color of traditional denim comes from the indigo dying process, which also explains why jeans get softer the more you wash them (we'll get to that part later).
The Creation of Denim
Denim fabric was created in the Middle Ages in France when fabric-makers tried to re-create a durable fabric from Genoa, Italy. Though they didn't get it quite right, their "serge de Nimes" (meaning twill fabric from Nimes) claimed its own place in the fashion industry and became Anglicized as denim. The famous trousers made from the fabric, originally called "waist overalls" by Levi Strauss, became known as "jeans" from the French name "Genes" for Genoa.
The fabric gained its blue coloring when dyed with natural indigo dye from India. Because indigo dye was expensive, the original denim makers used a waft weaving method that allowed them to use an undyed white thread for the back of the denim. Synthetic indigo later was created to make the fabric less expensive to make, but the popularity and durability of the style meant the weave never changed.
Washes have been applied to denim fabrics over the years to create varying shades of blue.
Why Blue Jeans Fade
The chemical reaction of indigo dying also leads to denim fading with many washings. In most dying processes, the dyes penetrate the fabric and the color remains consistent as the fabric wears. Indigo dye only binds to the outside of the thread, and small bits peel away through repeated washings.
This process also leads to denim products getting softer as they wear because the rough parts of the fabric peel away with the indigo dye.
Levi Strauss originally constructed its waist overalls in brown duck cloth and denim. Due to its softness and durability, denim emerged as the people’s favorite and the duck cloth fabric took a back seat. (But the softness and durability of denim won the popularity contest.) As historian Lynn Downey wrote “Once someone had worn a pair of denim pants, experiencing its strength and comfort – and how the denim became more comfortable with every washing – he never wanted to wear duck again; because with cotton duck, you always feel like you're wearing a tent."
Denim of Another Color
Denim gained new colors when manufacturers applied sulfur dying to the fabric, which allowed them to create black and gray denim, along with other colors that followed fads then faded away. One could argue that black denim is just as popular as the classic blue because of its versatility and ease of wear, as a darker denim in a classic cut can easily be dressed up or down.