Some fabrics simply cannot be fused - the combination of heat, steam and pressure required for a secure bond will damage their surface. Your sewing philosophy. Many couture sewers prefer the traditional tailoring method, which utilizes sew-in interfacing, rather than the speed tailoring method, which utilizes fusibles. While there are fewer sew-in interfacing varieties than there are fusible varieties, being sure you choose the one best suited for your project still requires a good understanding of their properties. When selecting an interfacing, consider the weight of the fashion fabric, the amount of softness or crispness desired, where the interfacing will be used in the garment and whether its care requirements are compatible with the fashion fabric.
Weight is usually the most important factor.
In general, the interfacing should be slightly lighter in weight than the fashion fabric. If the interfacing is too light, it won't provide shape and support. If it's too heavy, it will distort the shape of the garment. To test your choice, drape the fabric and the interfacing together over your hand and observe how they interact. Although a sew-in and a fusible interfacing may appear to be the same weight, the fusible will give a slightly crisper result.