Prewashing in Synthrapol helps remove invisible lubricants, fingerprints, dirt, oil, and other impurities that can interfere with the dye and cause uneven dyeing. Not pre-washing is one of the biggest causes of that "splotchy" dye job! Even PFD (prepared for dyeing) fabrics, yarns and clothing should be pre-washed! We never recommend skipping this step, especially with all the imported fabrics and clothing these days.
Synthrapol as the afterwash keeps loose dye particles of dye in suspension so they don't stain other areas of the fabric. So for tie-dyers, batik artists and printers: this helps white and lighter colored areas from being stained in the final wash by the excess dye. We get calls all the time about "muddy tie-dyes" - the secret is in the Synthrapol! (Also in the procedure for rinsing out the excess first!)
Use 1/4 cup (2 oz) of Synthrapol per washing machine load for cotton, Rayon, hemp, etc. and 1/8 cup (1 oz) for silks or front loading wash machines. Some folks say you can get away with less, but it depends on what you are doing, the hardness of your water, etc. (Look for special Low Foaming Synthrapol soon, better for those front loaders!)
