Cotton, wool, nylon + more. Celebrating a century. Rit Will Dye: Cotton; linen; rayon; silk; wool; nylon. Not recommended for synthetic fibers (acrylic, acetate or fabrics containing more than 35% polyester). Instead, use Rit DyeMore Synthetic Fiber Dye. package color reflects approximate results when dyeing white or off-white 100% cotton. Conforms to ASTM D-4236. Non-toxic + safe for sewage & septic systems. Before dyeing, visit ritdye.com for detailed instructions and a library of over 500 color recipes. ritdye.com. Made in the USA of US & imported materials.