Flannel Fabric
Cotton Flannel
Cotton flannel is what most people think of when they hear "flannel." It's the fabric of the classic flannel shirt and plaid flannel bedsheets. The cotton is woven (often in a twill or plain weave), then run through a brushing machine that raises tiny fibers from the surface. This nap traps air, providing insulation, and creates the soft feel. Cotton flannel is typically lighter than wool flannel and is washable, making it practical for everyday use.
Wool Flannel
Wool flannel is a different animal. It's a smoother, more refined fabric traditionally used for trousers, suits, and blazers. Wool flannel is brushed less aggressively than cotton flannel, producing a soft surface without a heavy nap. Gray wool flannel trousers are a menswear staple. Plaid wool flannel is used in sport coats and lightweight winter garments.
Weight
Flannel weight varies considerably. Lightweight cotton flannel (4-5 oz/yd) is suitable for shirts and light layering. Midweight (5-7 oz) is the most common for shirts. Heavyweight (8+ oz) provides significant warmth and structure. Wool flannel for suiting typically runs 10-12 oz. For bedding, flannel weight determines how warm the sheets feel — heavier flannel is warmer but also less breathable.
Quality Indicators
Good flannel has a dense, even brushing that feels soft without being thin. The fabric should feel substantial — if you can see through it easily, it's too thin. The plaid pattern, if woven (not printed), should be visible on both sides. Higher-quality flannel uses longer cotton fibers that produce a more durable nap that doesn't pill as quickly.