Rosco Flamex for Synthetic Fiber Fabrics - 1 gallon Treating synthetic fabrics can be difficult since the synthetic threads of the fabric do not absorb liquids in the same manner that a natural fiver does. Flamex SF is designed to be a penetrating treatment that to the threads deep withing the weave of the material. Can be used on many synthetic fibers and cotton/synthetic blends. One gallon covers approximately 500 square feet of fabric. It can be appied by Dipping, Brushing, or Spraying applications.