"The best fabric for iron-on patches is denim, cotton, or woven fabrics," says Sweeney. "Paint and fabric pens also work well on denim, cotton, fleece, and knits." Additionally, we don't recommend putting clothing labels on any delicate fabrics, as they may damage the fabric. We don't recommend using fabric markers on silk or sheer fabrics, as they may bleed. Sweeney also advises against using iron-on patches on polyester, nylon, or spandex to avoid melting the fabric. Most iron-on labels are made out of a polyester blend that's durable against washing and general wear. Peel-and-stick labels will adhere to fabrics like polyester, linen, and cotton. That style may not adhere well to fuzzy clothing items such as jackets, scarves, gloves, or sweaters.