Using Blowoff Tube to Harvest Yeast @ High Krausen

Hello people! I am currently brewing an english mild that is a little over 24 hrs. into fermentation. I'm brewing an oatmeal stout tomorrow, and would like to harvest some of the 1968 from the mild tonight to pitch tomorrow. I currently have a blowoff tube rigged (3/16) to the fermenter containing the mild. I'm wondering if I lower the blowoff tube into the krausen, would there be enough force to blow some of the yeast off into a container? Should I try this, or should I go ahead and use the beer thief method? Also, should I make a small starter for the yeast to keep fermenting overnight? Let me know what you guys think! Thanks

Unbeknownst to most people, collecting the blow off from a fermenting beer is not the same as top cropping and is not good brewing practice. Real top cropping involves removing the first 'dirt' or krausen - which contains weak or dead yeast, trub, and bitter compounds - and then waiting until the second (high) krausen to harvest. Ideally, you want to wait until the beer is just over 50% attenuated. This ensures you are harvesting the cleanest and most active yeast that share the same characteristics of the first generation.

With that said, wy1968 is not a good yeast for top cropping as it flocculates too fast and doesn't retain a top layer of yeast. Your best bet would be to wait until the fermentation is done to repitch some slurry or use another yeast.

alright thanks for the feedback... I'll head by my LBS tomorrow and pick up some fresh yeast. Thanks for the input!