PFD (Prepared for Dye) is off-white and chemically treated to absorb dye; Optical White is bleached to a bright white finish; and Scour (Natural) is washed but unbleached, retaining its natural tan color. PFD (Prepared for Dye): This is an off-white fabric that has been treated with a small amount of bleach to create a "blank canvas" for dye absorption. It is the industry standard for custom dyeing or screen printing. Optical White (Bleach): This fabric has been bleached to a true, bright white (similar to printing paper). It is a finished product and does not require further dyeing. Scour / Natural: This fabric is finished to its natural tan hue. While it can be used as-is for an organic look, dyeing it requires special formula adjustments to counteract the natural yellow undertones.