August 9, 2021

Materials Geekery: the Hand and Structure of Various Fabrics

holding up a section of 400d Halcyon in Night Walk to examine its color and hand.

 

Photo: holding up a section of 400d Halcyon in Night Walk to examine its color and hand.

Recently, someone asked: "I would love to understand a bit more about the fabrics you use for your bags - the 525 vs 210 vs Cordura vs Halcyon. In particular, I’d like to know how their structure results in the bags being the way they are, e.g. the 525 is so stiff and heavy; the Halcyon is flexible and light; the Cordura abrasive."

Here's our answer.

A lot of what we experience of a fabric, in tactile terms, is described as “hand” in the fabric industry. Also described variously as “drape”, or “heft”, it refers to the flexibility of a fabric (or lack thereof). Our stiffest fabric is our US 1050 denier Ballistic nylon, our 525 denier ballistic nylon is softer, and our Halcyon even softer.

In nylon fabrics, hand is mostly a factor of its thickness (weight, really), the innate softness or stiffness of its component fibers, and the amount of heat-setting it is subjected to in the final finishing of the woven fabric. Working in collaboration with our fabric mills, we have control over all these variables when we're ordering custom-woven and dyed fabrics as opposed to "stock" fabrics. The majority of our fabrics are custom-woven and dyed; one notable exception is our current 1000d Cordura fabrics, which are almost always stock fabrics. 

With custom-woven materials, we can specify the weight (a function of the yarn diameter and the density of the weave), what type of fibers (we can choose between yarns made up of many thinner, finer fibers, or fewer thicker fibers — both have advantages and disadvantages), and the amount of heat-setting done. It's intensely gratifying to have that much control over the materials we choose to utilize, and it's one of the reasons that the majority of our fabrics are custom produced for us: our experience and expertise allows us to create a material that we think will offer you the best experience. 

That said, we don't have 100% control. As we like to say around the factory, each weave lot and dye lot of any material can have minor, acceptable variations, almost as if each lot has its own personality. Much of weaving and dying materials is automated, though there is a degree of human expertise, intuition, and artistry involved — and that's how the personality of the material can appear. Though the procedures and work are very different, it reminds us of the experience of sewing bags at our Seattle factory — the flow of work is designed to be very efficient and replicable to exacting standards of quality. Though made on industrial sewing machines that require skill and expertise to operate and often the utilization of specialized folders and other parts, our bags are still, at the end of the day, hand sewn by people.

Our newest 400d Halcyon color — Night Walk — along with recently received deliveries of our Taiga and Black 400d all have a very, very subtle but interesting textural difference: the UHMWPE (ultra-high-molecular-weight polyethylene; read the 400d Halcyon entry in our Materials Glossary to learn more) yarns are ever-so-slightly raised. We thought it possible that the textural difference might actually increase the fabric's abrasion resistance, so we Taber-tested Night Walk and compared the results to previous Tabers of 400d Halcyon. The results? Same abrasion resistance. 

But we digress... back to answering the actual question: when nylon fabrics come off the loom, they are surprisingly loosely woven — you’d hardly recognize them! Heat-setting is a process that heats and therefore shrinks the fabric, making the weave tighter and “hand” stiffer — of course, you need to be careful not to over cook it, or the finished fabric can be board-like or paper-like.

One of the other factors in the experience of the finished fabric is whether the component fibers are texturized or smooth. 1000 denier ”Cordura” nylon is an example of a texturized fiber: air is blown through the molten nylon fibers as they are extruded and the result is that many of the fibers are broken, with the effect that the surface is perceived as “fuzzy”. Such texturized fabrics might be hard to distinguish from cotton canvas, and that's an aesthetic that many folks love. The broken or discontinuous fibers tend not to show abrasion, so while the scuffing might still be there, you won't notice it as much as you might with smooth fiber fabrics. One trade off is that texturized fabrics can, rarely but occasionally, cause thinner wool clothing to pill and abrade. You might also notice that texturized fabrics can collect pet hair, lint and snow.

We use a lot of smooth (also known as “filament”) nylon fabrics: all of our Ballistic nylons, Parapack, and Halcyon. We like how they don’t collect pet hair, and also how they slide easily in and out the overhead bin and other tight places.

Lastly, we use fabrics with three different weave patterns: 1x1 plain weave, 1x1 plain weave with a ripstop pattern, and ballistic or 2X2. Plain weave is the simplest pattern – just single yarns in the warp going up and over single yarns in the weft – nothing fancy. If you add a heavier weight yarn every so often (in both warp and weft, in a regular pattern) you can achieve a ripstop appearance: ripstop was developed for sailcloth, the idea being that if a tear was to start it would be stopped from spreading by the heavier (stronger) yarn. In our Halcyon fabric we use a yarn of UHMWPE instead of a heavier yarn of nylon: the UHMWPE is much stronger than nylon and gives the finished fabric an amazing tear strength. The UHMWPE doesn’t accept the dye used to color the rest of the nylon fabric, which is why the Halcyon ripstop is either white (its native color) or dark grey/black (color being added to the UHMWPE as it’s made). Lastly we use a 2x2 ballistic weave, wherein two side-by side yarns are woven as one. This increases the finished fabric’s abrasion resistance (we don't yet know exactly why: it has something to do with the energy absorbed by the two yarns sitting atop two other yarns.)

If you ask us what time it is, we’ll tell you how to build a clock. If you're as into this kind of stuff as we are, share your questions or topic ideas in the comments, and we'll add 'em to our list to respond to.

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We're the TOM BIHN crew: we design bags, make bags, ship bags, and answer questions about bags. Oh, and we collaborate on blog posts, too.