"Rayon is a semi-natural fiber - it is essentially re-processed cotton. Our rayon braid has more sheen and the colors available are a more muted palette. Polyester is an entirely synthetic fiber. It takes color beautifully so, our polyester braid is available in brighter colors. The sheen is slightly duller than that of the rayon. Please note the entire line of BeadSmith Soutache was designed by a textile jewelry artist for textile jewelry artist so tremendous attention was paid to consistency of width, thickness and drape so, the rayon and polyester braid can be used together successfully"