Regardless of the type of footwear, manufacturers use several different materials to construct uppers. Some materials, however, perform better than others. The following describes the advantages and disadvantages of the various materials used for outdoor footwear.
The most common types of fabric used for footwear are nylon, polyester and Kevlar. In many cases, the lining is made of synthetic material—often nylon or polyester—and the upper is made of leather. Occasionally, fabric is used on the top part of the upper, particularly for the gusset on either side of the tongue. Fabric is advantageous because it is lightweight, abrasion-resistant (with the exception of polyester), inexpensive and breathable, and provides consistent quality. Fabrics, however, have two major disadvantages: they are not waterproof, unless used with a membrane, and lack stiffness. It is therefore unrealistic to use only fabric in the construction of a hiking boot, as this would result in a low-end product.
Mesh
Polyester or nylon mesh can be used in the upper to provide breathability. It is lightweight and inexpensive, but is not water-resistant unless it is laminated onto a membrane. Manufacturers choose this type of material for certain types of footwear that require good ventilation.
Rubber
Whether natural or synthetic, rubber is a practical choice for the construction of an upper. It is entirely waterproof, can be moulded to different lasts, is sufficiently abrasion-resistant and is fairly inexpensive. Rubber is not, however, a malleable material. It can be folded or stretched, but will always resume its original shape. Although waterproof, rubber is not breathable. It offers no ventilation and does not wick away moisture. Rubber is also heavy compared with other available materials. Finally, rubber cannot be used alone because it is not resistant to tension and stretching. It must therefore be laminated onto another material. Rubber is often used for the rand—the protective band that runs the distance around the junction of the upper and the sole. Sometimes, this band covers only the toe cap, which often shows the first signs of wear.
Waterproof-breathable membranes
In order to make a boot completely waterproof, some manufacturers add a waterproof-breathable membrane between the lining and the top of the upper. Such membranes, which are never visible, cannot be considered structural components of the footwear. They are hidden beneath the surface because they are not abrasion-resistant. Most boots that have such membranes are made of fabric and/or leather. Since fabric is not waterproof, the membrane helps keep feet dry. Moisture and heat can escape, however, since the membrane allows water vapour and air to pass through. It is important to keep in mind that waterproof-breathable membranes cannot perform miracles. If the top of the upper becomes saturated with water, moisture inside the footwear will become trapped. If the membrane is used with a leather upper, the leather must remain dry in order for the membrane to be effective. Consequently, the leather must be treated with waterproofing agents. This treatment will, however, render the membrane practically useless. These membranes are especially effective when used in combination with fabrics that are breathable, but not waterproof.
Plastic
Plastic is rigid and can be moulded to the boot last. If offers tremendous support, but little flexibility. For this reason, it is used mostly in the heel counters and toe caps of conventional hiking boots. Plastic is also frequently used for mountaineering boots, along with an inner boot.
Synthetic leather
Synthetic leather resembles genuine leather in appearance only. Since it is not porous, it hardly absorbs water. Contrary to genuine leather, synthetic leather will not stretch or soften when wet. As a result, it provides the same support, wet or dry. Since it does not stretch, however, it cannot be used as a lining. Since synthetic leather is not made up of densely blended fibres like leather, it is less resistant to wear. Genuine leather fibres will move and stretch under the force of friction, while synthetic leather will simply wear out. For the same reasons, synthetic leather does not wick away perspiration as effectively. A leather boot can be maintained and its properties more or less well preserved for a very long time. Synthetic leather cannot be maintained in the same way and will eventually become brittle, hardened and cracked, especially when exposed to ultraviolet rays.
Leather
Leather, in all of its forms, is undoubtedly the most commonly used material in the construction of hiking boots. Although there are as many types of leather as there are animals, cowhide is most often used for outdoor footwear because it is thick and sturdy, and readily available. A hide must undergo many processes, including tanning, before being made into leather. At a certain point in the processing, the hide is split into two or three layers to obtain a greater usable surface, except when manufacturing full-grain leather, when the entire thickness of the hide is used. The appearance and properties of leather vary considerably, depending on how the pieces are used—rough-out or smooth-out finish—and how they are tanned. The following diagram illustrates the different parts of a hide and the resulting types of leather.
