"Wonderful post, always find this site to be a reputable source of the latest information and technique. I found this article because I was trying to buy some sift screens and so far the best I can find is a 4 screen system that has the following micron equivalents, 250, 165, 149, 75. By Robert Clarke's guide, this is lumping in "large plant debris" with all the resin heads then the bottle screen of under 70 is going to collect essentially nothing... but "very small debris and little resin". If I am understanding this correctly, any idea why the construction of these screens is so misguided?"