We currently use Whatman 800µl UNIFILTER GF/F 96-well plates for purifying DNA under the Qiagen DNeasy tissue extraction protocol. We have commonly observed holes forming in the filter membrane which we believe is related to the centrifugal force. However, Qiagen's protocol recommends long spin times to ensure evaporation of ethanol in the wash buffer and complete binding of the lysate which are also above Whatmans recommendations. Does anyone know what kind of impact the hole formation has on DNA retrieval or how to resolve it?