The 3M Shortening Monitor is used by dipping the strip into hot shortening until all four blue bands are submerged. After the strip is removed, the number of bands observed to change from blue to yellow indicates the exposure to a specific free fatty acid (FFA) concentration. For instance, if the bottom band completely changes from blue to yellow, but the top three stay blue, then there is a greater than 2% free fatty acid concentration but less than 3.5% FFA. As an operator, you can use the 3M Shortening Monitor test strips to determine the discard point for your shortening.