The earliest examples of backpack fabrics used were cotton canvas waterproofed with a heavy wax coating. While these backpacks displayed excellent weatherproofing characteristics the fabrics were heavy, prone to abrasion and when stored wet would rot. Although there are very few canvas backpacks manufactured today, there are some backpacks made from technologically advanced canvas materials, which promote the combination of synthetic materials to improve the strength and water
resistance of the canvas fabric. However, backpacks made from cotton canvas in general are not usually waterproof and apart from some limited brands, the only place you are likely to find backpacks made of this material is possibly the military. (Although, even the military are now replacing canvas backpacks with Polyurethane coated Cordura® Nylon, Kodra Nylon, or other Nylon fabrics). Due to a lack of waterproofing and a ready ability to absorb water or moisture, especially
in less expensive materials, cotton canvas is not a preferred backpack material. Its main advantage is that it is generally inexpensive and backpacks made of this material are cheaper as a result. This does not suggest there are not better canvas fabrics available, but these technologically advanced fabrics are expensive and inherently heavy.
A characteristic of the Cordura® and Kodra material is the rough fuzzy texture. These materials are some of the most sort after fabrics in use today for high quality backpacks. The main advantages of Cordura® or Kodra fabric are its abrasion resistance and the fact it is relatively lightweight when compared to canvas materials. Cordura® or Kodra is not as puncture resistant as a heavy weight Oxford Weave Nylon and does not waterproof as well as Nylon, but both Polyurethane
coated Kodra and Cordura® are considered waterproof. The main advantages of Cordura® or Kodra fabric are its abrasion resistance and the fact it is relatively lightweight when compared to canvas materials.
Cordura® is the brand name for a collection of fabrics used in a wide array of products including luggage, backpacks, pants, military wear and performance apparel. Cordura® fabrics are known for their durability and resistance to abrasions, tears and scuffs. Originally developed and registered as a trademark by E.I. DuPont DE Nemours and Company (DuPont) in 1929, it is now the property of Invista (a wholly owned subsidiary of Koch Industries, Inc.). Cordura® fabrics are
made using yarns or fibers from Invista. Fabrics can be made using 100% synthetic fiber or in blends with cotton or other natural fibers. To display the product hangtag to use the Cordura® brand name, each fabric should be and approved by Invista. More information can be found on their website at http://www.cordura.com/
Kodra is no longer a registered trademark, and although originally manufactured by Kolon Industries Inc., a product used in the manufacture of all White Mountain Backpacks™, it is now a brand name used by many manufacturers. It is for this reason White Mountain Backpacks™ will from 2016 use only Invista Cordura, as we can longer guarantee the source of the Kodra material.
Another material, Polyester Pack Cloth has a higher resistance to ultra-violet (UV) degradation, however Nylon materials are still a stronger fabric. The advantage of Polyester over Nylon is that it is cheap, therefore polyester and textured polyester pack cloth made to look like Cordura dominates the low price end of the market, where nylon dominates the upper end of the world market.
Polyurethane coated Nylon fabrics came to replace cotton canvas, but earlier fabrics were heat bonded to the Polyurethane and failed to deliver on the promise of revolutionary and superior performance. Heavy usage inevitably degraded the fragile heat bonded Polyurethane coating on which these Nylons relied for waterproofing and delaminating was the inevitable result. Now all premium Nylon materials are cold bonded, providing a superior resistance to delaminating and as in the
White Mountain Backpacks™ materials, double coated for further wear resistance.
Rip-Stop Nylon has emerged in the marketplace replacing the standard Nylon. It is easy to distinguish Rip-Stop Nylon from standard Nylon by its regular grid pattern of heavy threads sewn in the warp and weft of the fabric at regular close intervals. The heavier threads prevent further ripping if the pack is punctured or torn. Nylon when torn has a tendency to continue ripping under the slight. pressure, or can start unraveling. If you are deep in the backwoods with no thread,
dental floss, or duct tape, a torn pack can present an unwelcome challenge. A torn Nylon backpack put under stress by 20 kilograms of equipment can quickly start to come apart. The rip-stop design can provide extra protection to help ensure that your pack will not disintegrate in front of you. The main advantages of rip-stop nylon are a ready acceptance of waterproofing and it is relatively lightweight. However, if Rip-Stop Nylon is used in lighter fabric weights, holes from prolonged
abrasion may appear sooner than in Pack Cloth Polyester. While Rip-Stop Nylon is increasingly appearing in upmarket backpacks in the US, it has already established a large market acceptance in Europe.
Over a long period of time all synthetic laminated backpack materials are prone to the delaminating of the Polyurethane Coating. This can occur naturally or be hasten by exposure of the Polyurethane Coating to direct sunlight for long periods, harsh chemicals used to clean the pack, long periods of exposure to salt water, exposure to swimming pool chlorine (rinse well immediately and dry thoroughly by hanging in a shady area after immersion in seawater or exposure to chlorine)
, or long periods of storage in either damp or occasionally damp areas, particularly on cement floors. When put in storage the backpack must be 100% dry and preferably stored hanging so air can circulate around the backpack.
Be assured that currently White Mountain Backpacks™ only use highest quality synthetic materials supplied reputable suppliers who guarantee the latest technologies in the manufacture of these materials.
A little common sense will prevent premature aging of the synthetic material's Polyurethane Coating. Always clean and dry your White Mountain Backpacks™ backpack before you put it away. Never pack or store your White Mountain Backpacks™ backpack if it is dirty or damp. Wet synthetic material can mildew which causes delaminating, leaks, and foul smells, and there is no cure for delaminating and mildew damage.
Storing your pack while it is damp will cause the Polyurethane Coating to soften and stick to itself (a chemical reaction called hydrolysis). With prolonged exposure to moisture, the coating will peel away from the fabric and create leakage.
All Polyurethane Coated synthetic backpacks with an internal eventually wear out, in that the material lamination will eventually fail. Generally most backpacks will have worn out before delimitation takes place. However, with the quality of a White Mountain Backpacks™ backpack this isn’t the case.
We are confident that the synthetic materials we use will outperform all other comparable products, however, mildew damage and hydrolysis (delaminating) are not covered by the White Mountain Backpacks™ Lifetime Warranty.
Further information on PU Coating delaminating and restoring the waterproof coating
The definition of "Denier" is a measure of fiber fineness: a unit of fineness of silk and some artificial fibers, such as Nylon, equal to one gram per 9,000 metres of yarn. The strict definition of denier is the weight in grams of 9,000 meters of the yarn. For example, 9,000 meters of a 450 Denier thread weighs 450 grams. Denier is a direct numbering system in which the lower numbers represent the finer sizes and the higher numbers the coarser sizes, for example a 450 denier yarn
is twice as fine as 900 denier yarn. Material Weight or Fiber Thickness is an important consideration in the materials utilized for backpack construction. It is obvious, that the higher the Denier in a particular material the higher the strength of the fabric, and the higher the weight as well. Most of the higher quality backpacks identify the denier of the material on promotional information. Does this mean a higher Denier is better? Not necessarily, this would depend on the material,
for instance 600D Polyester Material would not be as strong as 420D Nylon Material.
There is an additional factor you should be aware of - tenacity. Tenacity is a measure of the fabric's ability to resist additional tearing once a tear has started. Nylon is available in two types of tenacity. Type 6 Nylon commonly used in backpacks and classified as low tenacity, or lower strength nylon (tenacity of 3.0 to 6.0 grams per Denier), or Type 66 Nylon considered high tenacity and is much stronger (tenacity of 6.0 to 9.5 grams per Denier). Can you tell the difference?
Unfortunately, there is no way to tell the difference without testing the material in a laboratory.
You'll find most backpacks are sewn at 6 to 10 stitches per inch. The general consensus here is that, if the stitching is increased much beyond 10 stitches per inch the strength of the fabric begins to degrade. Anything below 6 stitches per inch begins to become suspect in terms of strength. Be aware that backpacks are made of deniers much higher than you'll find in a tent or sleeping bag, and close stitching can actually damage the threads used in the backpack fabric itself.
Another factor is the twin stitching method, where all stitching is doubled stitched for added strength, including the zippers attachment to the backpack. Constant zipper use on less expensive backpacks with single stitching can cause the zippers to be pulled from the backpack, an all too common problem.
All White Mountain Backpacks™ utilize high quality YBS zippers and all backpacks are twin stitched at 8 stitches per inch. YBS zippers are manufactured in Korea and are reputably equal to YKK zippers manufactured in Japan.
The majority of backpack manufacturers and White Mountain Backpacks™ use plastic "coil" zippers on their backpacks. A coil zipper is basically a continuous piece of plastic that's been formed into a coil shape and sewn onto a piece of fabric webbing. The main advantage of the coil zipper is that if fabric gets caught in the teeth, the fabric can be gently pulled out without tearing. This is certainly a consideration since your pack will sometimes be crammed with clothing,
a sleeping bag, or nylon bivvy bags.
Some backpacks may have regular solid tooth zippers, and these are certainly okay as well. These zippers won't let go of fabric that easily, but size for size, they're stronger than coil zippers.
Other really inexpensive backpacks may use metal tooth zippers in either steel or aluminium, which can either rust or corrode badly when exposed to rain, sea air, or worse salt water, and are not recommended.
There is also Water Repellent Zippers for backpacks available. However choose carefully, as these zippers generally have installation restrictions, some are subject to damage from heavy items placed on the zip, require careful use to avoid damage and misalignment of zipper teeth (sharp bending or twisting should be avoided), and some are also prone to damage by heat, humidity, and direct sunlight.
Waterproof zippers are available, but not generally used in backpack production, as the zipper cost would be greater than the retail price of the backpack.
More about zippers in Do It Yourself Repairs, Zippers.
The thread used in the manufacture of backpacks is an important consideration, a factor that is often overlooked and frequently not mentioned. Many less expensive backpacks made from quite acceptable backpack fabrics, but come apart under load simply because an inappropriate thread was incorporated into the finished product.
White Mountain Backpacks™ use a high quality nylon thread that is virtually unbreakable!
Open Cell Foam has interconnected air chambers throughout the material, which produces an extremely soft and highly compressible foam. Open Cell Foam is used in the construction of many high quality self-inflating camping mattresses. Whilst Open Cell Foam is very comfortable, self-inflating air mattress have a layer of air that provides support and insulation properties, and is highly compressible once the air is released. Open Cell Foam is not very good as a solitary padding
material for backpacks. The high compressibility of the Open Cell Foam can cause shoulder straps and hip belts to over compress under load, providing minimum of comfort. While the padded straps may look great and feel wonderfully soft at the time of purchase, this will not be the case when the backpack is under full load. Determining whether the padded straps are Open Cell Foam is easy enough, simply squeeze with you hand, and if the straps compress to less than one half of the original
size it is Open Cell Foam.
Ensolite or Closed Cell Foam has open air chambers surrounded by foam that are not interconnected. The completely encapsulated air cells in the Ensolite Foam do not compress easily yet provides good padding. Ensolite or Closed Cell Foam is used in the production of Closed Cell Foam mats and its construction prevents full compressibility.. Since the Ensolite or Closed Cell Foam is a rubber based material and has completely encapsulated air chambers, it provides excellent insulation
and absorbs very little water.
For many years, better backpack designers cut and sewed the Ensolite or Closed Cell Foam into fabric sleeves providing the main source of shoulder and hip belt padding. The foam is dense, impervious to perspiration, and very comfortable. Ensolite or Closed Cell Foam is the main material used in backpack padding today, and it is a perfectly good material for backpack straps and hip belts. Determining whether the padded straps are Ensolite or Closed Cell Foam is easy enough, simply
squeeze with your hand, and if the straps compress very little, then it is Ensolite or Closed Cell Foam.
Concluding that Open Cell foam is more comfortable next to the body (more compressible, therefore softer) and Ensolite or Closed Cell foam is better next to the load (less compressible, therefore firmer), several manufacturers use Dual Density Foam in padding their backpacks. Backpacks with Dual Density Foam capitalize on the advantages of both foams, placing the Open Cell Foam against the body and the Ensolite or Closed Cell Foam against the load. This combination is more comfortable
than either Closed Cell Foam or Open Cell Foam, supporting the load well and providing comfort for body.
Currently all White Mountain Backpacks™ are manufactured with high quality Dual Density Foam.
One manufacturing drawback to Ensolite or other Closed Cell Foams concerns the manner of its fabrication. The material is typically poured into a frame and cooked into flat sheets that are cut to size, then cut to create a desired shape. The cost of cutting and shaping foam is highly labour intensive and results in significant material wastage. Because of these reasons another process was developed for the shaping, forming and customization of the next generation of foam, Compression
Compression Moulded Foam originally appeared in European backpacks in the late 1980's and used a different manufacturing technique. The outer nylon material is adhered to a block of polyethylene foam using a heat sensitive adhesive, and then the entire assembly is heated so that the foam and adhesive soften. At this point, the assembly is compressed into a shaped mould to provide the final product. The shaped hip belt, shoulder strap, or lumbar pad is then cooled to resolidify
the foam and adhesive. The final product is a pad shaped into a customized form.
Compression Moulded Foam is Ensolite or Closed Cell Foam, although slightly lighter in weight and shaped to the body without cut edges. An added benefit is the cavities formed inside the moulded foam pads, and different densities of foam can be included to provide flexibility to the final shape.
White Mountain Backpacks™ don't sell backpack fabric, as these are not available as a distributed item. Your local Canvas and Material Supplier should have a similarly appropriate material for your purpose.