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Monday, July 20, 2015

Recycling: Color Stripping & Dye Removal Index

In 1993, a dye removal index (DRI) was put forth by Patrick Sharpe & Randy Lowe to study color stripping efficiency.  The percent color removal is calculated from the dye removal index as follows:


When DRI is calculated for each bleaching step, the value obtained is intended to be an indicator of the percentage of total color which has been removed.  Since DRI is a single variable parameter, it yields no information regarding the direction of the color shift which takes place from one bleaching step to the next.

What is your experience with DRI?

Reference: Patrick E. Sharpe and Randy W. Lowe, "The Bleaching of Colored Recycled Fibers", TAPPI 1993 Pulp Bleaching Conference Proceedings, Book 3, PP 1205 - 1217 (Nov. 1993).