Open fermenting lager

An actual brewing post!

I've been experimenting a bit lately with open-fermenting lagers. It was a suggestion from Kris (lately of PDBC) that I thought I would try.  He's right, many of the classic German lager beer producers historically did open fermentation in lined tanks. Some still do. Not that I'm an expert, but many have told me this, and New Brewing Lager Beer has a few good passages on it. Good enough to try even though it goes so strongly against the "keep it closed, keep it clean" mentality that's been hammered into my head.

Very simple open fermenting.  Just skim the head.

While I don't have lined tanks, I do have a handy plastic fermentation bucket which fits just about as well in my beer fridge as my glass carboys do.  Just put the lid on loosely without locking it down, and let it ferment nicely during primary before transferring to glass for the longer, colder secondary stage.

What does this do?  I suppose it allows theoretically for better uptake of oxygen during the aerobic phase of yeast growth and development.  But to my mind really the key is that it allows easy access to skim the foam head and braunhefe that develops daily during the very active, high krausen phase of fermentation.

And why does that matter?  Well, try some.  Seriously.   Intensely unpleasant, mouth-coating, lingering bitterness from hop residues accumulate in that head.  What I do is sanitize a long-handled stainless spoon in Star-San, then just skim off this very thick head about once a day during active fermentation.  (By the way, braunhefe refers to the brown-tinged scum that comes up as well -- you can see it in the picture.  The brown color apparently comes from degenerated yeast cells.  The color gets less and less pronounced each day, but the head remains quite bitter.)

And the result?  I have to try it a few more times before I'm ready to have a firm opinion.  At least, I'm convinced of the importance of skimming the very bitter head from my lighter, more delicate lagers.  So far, the helles shown in the picture (now lagering happily) is really good.  If anything, the schwarzbier I made before that might be too clean though.  This technique does seem to reduce overall perceived bitterness in the finished product, and I have yet to nail my adjustments for that.