Originally Posted by bearisgray http://www.prochemicalanddye.com/store/home.php?cat=323 The directions for both say to use HOT water (140 degrees F., 60 degrees C) The instructions for Retayne suggest treating the fabric BEFORE cutting it. Retayne - soak fabrics for 20 minutes in hot water, then rinse Synthrapol - soak 10-12 minutes in hot water, then rinse. As far as I can tell from that info, they are NOT interchangeable.