One of the most reliable post-fermentation fining agents for reducing polyphenols is PVPP known as Polyclar. A micronized white powder with a high surface area to volume ration, Polyclar readily absorbs polyphenols including tannins. It will also slightly reduce bitterness while lightening the color a shade. Used at the rate of at the rate of 2 Tbsp for a 5 gallon batch. The necessary contact time is only a few hours. The beer should be racked off the sediment prior to bottling or kegging.