The directions for the Retayne say to use for fabrics which might bleed...will help set in the color. Synthrapol says will help pull out excess dyes, such as those used in hand-dyed fabrics like batiks. This is how I've used them.

I was intrigued by the use of the Retayne for all fabrics across the board prior to use, and for the use of Synthrapol once a quilt is completed.

Nevertheless, here is a link to the products' page which gives instructions on their uses: