Twill, denim, drill, and whipcord are examples of diagonal weaves. Diagonal weaves are strong, but may have poor abrasion resistance. These fabrics vary in weight depending on the ply of thread used. Fabrics in which the threads pass over more than two or three threads will usually wear more quickly than a plain weave fabric. When selecting fabric for outerwear, consider the following characteristics.
Porosity is a fabric's ability to allow air to pass through.
Low porosity fabric will keep out water and wind, and will also help prevent down or other insulation from leaking through the fabric. To check the porosity of a fabric, hold a sample against your mouth and blow through it. If the air is contained, the fabric has low porosity. Another way to check is to hold the fabric up to strong light and observe the amount of light that shows through. Except for rainwear, outerwear fabrics should allow some porosity for body moisture to evaporate.