Bags are subjected to a lot of physical stress throughout their lifetime. As we design new gear, we're making sure that our choices in materials are a good match for the the intended use of our equipment. While it's a labor of love to go through all these amazing textiles, it also ensures that these bags will perform as promised.
There are a ton of different ways to measure a textile's properties, but we're going to focus on the attributes we look at the most.
This is where we usually start when looking at a fabric. This is literally the weight of the material per area. This is typically measured in oz/yd² or g/m². This is one of the first metrics a user will notice about the bag. For technical applications, the fabric weight can have a huge impact on the overall experience with the bag.
A side note on Denier: This term often gets thrown around (us included) as a reference for fabric weight or thickness. You may have heard 1000D nylon or 410D pack cloth in a bag description. What denier refers to is the mass of the yarns or filaments used to make the textile. Often it's good short hand for the overall weight or hand-feel of a fabric, but I've felt plenty of 400D fabrics that can look heavier or out-perform other 600D fabrics. The way the yarn is spun, woven and material have a huge impact. So you can have a very fine 600D and a very coarse looking 400D.
This is the second metric we usually check. Abrasion is the amount of rubbing the fabric can handle before a material failure. This test is performed by rubbing the fabric against itself in a controlled process to test durability. The test results are the amount of rubs or cycles before the fabric is unusable. When we're looking at a fabric, we often start by checking the abrasion resistance against the weight to see if the material has a good efficiency.
This is the percent of elongation (stretch) before the the material fails (breaks). Most of the time we're looking for materials with minimal elongation so the pack does not distort. However there are times when high elongation is good, like a stretch pocket.
This measures a textile's resistance to tearing...you probably guessed that much. It can get a little tricky because some textiles may tear at one force but will only continue to rip if additional force is applied. In rip-stop nylon for example, a tear will stop at one of the thicker (rip-stopping) yarns. Easily tearing fabric will quickly show itself in the field and can quickly render a pack unusable.
There are a lot of different ways to test water resistance. Most measure variables like water pressure and time. The majority of the textiles we use have a polyurethane lamination on the back side of the fabric. This layer provides waterproof-ness that can stand up to a heavy downpour. Other fabrics have a lamination of polyester inside or on the back of the textile to achieve the same goal.
This stuff is gorgeous. X-Pac is a broad term used to describe a lot of different offerings from a company called Dimension Polyant Inc. The company is best known for making high performance sail cloth, but in recent years they have started making textiles for the outdoor industry that use their specific technologies.
X-Pac textiles offer really great strength, water and abrasion resistance while staying very light weight. For this reason, much of the ultralight backpacking community have really embraced these materials.
A perennial favorite for outdoor makers and consumers alike. Just to be clear Cordura is a brand name applied to a variety of textiles from different mills. My understanding is that mills can have their materials certified as Cordua by the brand's owner, Invista, if they meet strict testing requirements. This still means Cordura stands for great quality and durability but it is a brand, not a specific fabric or mill.
Cordura is one of our favorites too because of its great abrasion resistance, relatively light weight and its soft, canvas-like hand-feel. When starting to sample a bag idea, these are some of first fabrics we reach for.
This sounds a bit dense (joke), but stay with me. At the risk of greatly oversimplifying this, UHMWPE is a very strong plastic. In recent years it's been made into a number of textiles sometimes comprising the majority of the material and other times, it's combined with nylon or polyester as a reinforcement. This stuff is great. When a really high strength to weight ratio is needed, this material performs very well. Some ultralight backpacking brands use it almost exclusively.
Certain textiles that incorporate UHMWPE are branded as Spectra and Dyneema. These brands feature amazing textiles that are used in everything from armor to climbing rope and really shows the capabilities of new material technology. We don't use these materials too often, but when keeping weight down is paramount this is a really good option.
With all this tech talk, it's important to remember that even a basic mid-weight nylon offers some amazing performance. While not as techie sounding, light weight and mid-weight nylons offer great strength to weight characteristics and, when coated with a polyurethane, the material will stand up to a downpour just fine. We keep these on hand and use various nylons throughout the bags.
This stuff is crazy durable, and if you've ever owned a big messenger bag, you've probably owned some of this material. The tarp comes in different weights and is extremely durable due to it's composite construction. The polyester weave inside provides tensile strength and flexibility, while the vinyl acts a tough outer membrane. This material is great for high-wear areas or places like a flap, where we want to give a weightier feeling. Although very durable, we don't use it too much because of the weight-add.