All About Denim: Understanding this Classic Textile

Stacks of denim fabric by the yard

Denim holds a special place in our hearts at Core Fabrics, which is why we've created the Denim Zone on our website. This curated space is filled with expert insights, helpful videos, and tips to find the perfect denim for your project. Don't miss out - it's a denim lover's paradise!

Back in the day, Closet Core was one of the first companies to introduce sewists to Cone Mills denim, and at Core Fabrics we continue to stock it when we can get it, in addition to beautiful upycled, sustainable and deadstock denim fabrics by the yard. I built the Closet Core brand on jeans patterns (Hi Ginger! Hi Morgan!) so denim is something I know and love. Here is everything you need to know! 

What is denim?

Denim is dense, durable fabric woven in a diagonal twill pattern. It gets its strength and durability from a combination of weave and fiber. Strong cotton thread is woven into a twill pattern, with more warp threads than weft. The vertical warp yarns are often dyed with indigo, while the horizontal weft yards are left white. This creates that classic denim depth and texture we know and love.

Different denim fabrics by the yard

Denim Twill Weaves

Lighter-weight denims are generally a 2x1 twill, meaning there are two warp threads for every weft thread. Medium and heavyweight denim employ a 3x1 twill, with three warp threads creating an even more dense, resilient fabric.

Twills can also be broken down into left-hand, right-hand, and broken twill. Right-hand twill has a diagonal pattern that travels from the bottom left to the top right of the fabric and is the most common. It tends to show fading and whisker lines from lots of wear. Left-hand twill is less common; it’s woven in the opposite direction of right hand twill and has a softer hand. Broken twill means the warp threads alternate to create a zigzag pattern. If you’ve ever had an issue with your jeans "twisting" in the leg, its because the the denim is pulling towards the direction of the weave.

Hot tip: broken twill weaves are less likely to create leg twist.

Types of denim - understanding denim weights

Understanding Denim Weight

Folks get confused about fabric weight, but it's important to understand how weight is calculated so you make the right choice for your project. Fabric weight is calculated by ounce per square yard, or gram per square meter. Here are some general rules:

  • Lightweight denim is anything under 9 oz (9 oz/sq yd). While you can make lightweight, stretch jegging like jeans with denims under 9 oz, denims in this category are going to be better for shirts, dresses and lightweight pants. A typical denim shirting has a weight of 6 oz, for reference.
  • Mid-weight denim is 9 oz to 12 oz. A good all purpose weight is 11 - 12 oz. These have good structure and heft without being too stiff.
  • Heavy weight denim starts at 12 oz, and can go as high as 32 oz (I have seen some jeans made with denim so heavy they can literally stand up on their own!) Anything over 18 oz is going to be too heavy and thick to be comfortable, and is better left for home decor or upholstery applications.

Types of Denim

 There is a lot of denim terminology out there and it can get a bit confusing. Here are the most common types of denim out there.

  • Non-stretch denim is just what it sounds like! It is generally 100% cotton (although you can also find some hemp and viscose denims these days) and has no natural mechanical stretch, great for overalls, jean jackets, jeans (obviously), workwear, or any garment where you want something super durable and hardwearing.
  • Stretch denim fabric has a bit of lycra woven into it, generally 1-8%. This is the kind of denim uses for skinny jeans. While we are generally anti-polyester around here, poly woven into stretch denim is actually a good thing. It helps stabilize the cotton to prevent it from stretching out, which means your jeans last longer and get more wear, always a good thing in our books!
  • Selvedge or salvage denim is a type of (mostly) non-stretch denim. It has a distinctive selvedge edge which is typically white with a coloured yarn line running along the sides. This occurs from the way it's woven on traditional looms. The weft threads are woven around the end rather than being cut like on modern looms. Selvedge denim tends to be quite narrow at 30-35" wide, and since it's generally made on slower, old fashioned looms it's often more expensive. It's not the best choice for womens jeans since it requires a completely straight side seam in order to see it as a detail. If you have hips and want that selvedge detail, you will have to make some serious pattern mods.

  • Bull Denim is typically a denim that has been woven with the same weft and warp thread colours; this way the denim can be dyed in solid colours. It sometimes means a very durable denim.

Where is Denim Made?

Denim was originally milled in De Nîmes, France (Denim - get it?) in the 19th century. Once workwear started being produced in earnest, most denim production moved to the United States, and for decades some of the finest denim in the world was being produced in the US. Unfortunately most of those mills have now closed, with the iconic Cone Mills White Oak plant shuttering a few years ago.

There is still some small batch production happening but far and away, denim is now produced overseas. The highest quality, cultiest stuff comes from Japan. The Japanese love denim so much, they bought up many of the old fashioned looms from American mills and are some still using them today (some of them were even tool and dyed from scratch!)  Italy, Spain and Turkey also make gorgeous and innovative denim as well.

Is Denim Sustainable?

Unfortunately, most denim production is incredibly resource, energy and water heavy. Non-organic cotton can be very destructive, and many mills are producing denim as cheaply as possible without regard to the environmental consequences.

As a result, we are always on the hunt for innovative producers who are trying to make this classic textile in new and improved ways. Our upcycled denim is produced at a family run mill in Guatemala using recycled textile waste, and we are always buying up high quality deadstock when we find it. One of our longterm goals is to find a highly sustainable mill we can start sourcing regular goods from, and we are currently testing a few mills for quality, so hopefully we can report back!

While you'll often hear that jeans production is one of the most environmentally destructive garments produced, the good news is that that refers to the finishing as well, and it's the post-finishing process for jeans (to create distressing, fades etc) that are often the biggest culprits. Choosing to make your own jeans and letting them develop their own natural patina and wear patterns is a great way to make jeans a bit more friendly to the earth.


That wraps up our deep dive into denim fabric! Please let us know if you have any comments or questions, and be sure to check out our denim zone and ever changing collection of denim fabric by the yard!