Procion MX Fiber Reactive Dyes – The Ultimate Choice for Tie-Dye, Batik Shibori Procion MX dyes are professional-grade fiber reactive dyes that bond permanently with natural fabrics, delivering intensely vibrant, washfast colors. Unlike traditional dyes that require heat, Procion MX is a cold-water dye that fixes chemically, making it the gold standard for backyard dyeing, batik, tie-dye, and shibori.