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Old 05-09-2011, 04:05 AM   #1
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Default Question about lager fermentation

Sorry for the long post, but I figure if I'm going to ask for help, I should give as much detail as I can.

I'm fermenting my first lager now. This was one of those $20 anniversary kits from AHS, so I bought the extract kit with grains even though I normally do all grain - figured it'd be a cheap way to try a lager for the first time since the extract kit was priced the same as the others. I used 2 packs of S-23 for this 1.052 OG pilsner (5 1/4 gallon batch). After the boil, I threw away the AHS instructions which had called for pitching warm, then cooling. I cooled the wort to 50 F and while it was cooling I rehydrated the yeast at 72 F, fed it a small amount of wort and cooled it over about a 4 hour period to about 48 F and pitched it. I wasn't sure whether or not to aerate with dry yeast (I've read pro and con) so I gave it about 45 seconds of O2 through a .5 micron stone just before pitching.

I set my Johnson controller for 52 F, so the beer spent most of the time at 50-51 F. Fermentation kicked off within 12 hours and proceeded at a steady pace (about a bubble every 2 seconds from the airlock) for about 5 days, then began to slow to one bubble every 4 seconds. I raised the temp setting by 1F - the next day it was one bubble every 6 seconds, so I raised the temp setting another 1F to 54 F. Later that same day (eighth day after pitching) I decided it was time to check if it was time for the diacetyl rest, so I took a hydro sample - gravity was 1.020, so I started the D rest.

The hydro sample tasted very good - I didn't detect any diacetyl, but I don't exactly have a trained palate. I decided to go ahead and do the D-rest as I figured it wouldn't hurt anything, so I raised the temp. setting to 62 F (another question - I've read D rest temps should be anywhere from mid-50's to as high as 68 F - I split the difference). On the morning of the next day (ninth day after pitching) the airlock was bubbling once every 6 seconds, but then later that day there were no bubbles at all (it's still air tight because I can squeeze the Better Bottle and change the level in the air lock). No bubbles since then - not one! No, I haven't taken another hydro sample yet - I don't want to do that until I rack it to a keg for lagering - I'm trying to avoid oxygen exposure.

I'm assuming fermentation is finished (expected FG is 1.013), but I'm just surprised at how suddenly the bubbling stopped - I'm used to ales where the bubbles slow down gradually over a period of days. And yes, I know people say that bubbles don't mean anything, but for me they've always been a good general guide for how active the fermentation was going.

So my questions are:
1. Is this sudden and complete cessation of activity normal?
2. Assuming I have reached FG when I take my sample in another day or two, should I bother slowly ramping down to lagering temp, or just crash cool it?
3. Should I have aerated with dry yeast?
4. What is the recommended D-rest temperature?

Thanks for your help.

EDIT: one more detail - the krausen, which was about 3/4 inch thick during primary fermentation has fallen back - now there is only a thin tan colored film covering the total surface area - thin enough to see through in places.


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Old 05-09-2011, 04:33 AM   #2
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I'm sure someone who brews lagers more frequently than I can answer some of those questions for you.

Regarding yeast aeration, I know Danstar says you don't "need" to aerate when using their yeast, but every other manufacturer recommends it. You can't over-aerate your wort (unless you really try to, and even at max saturation it would probably off-gas or be consumed quickly), and it's better to have enough O2 than not enough.

Regarding cold crashing, I was listening to Charlie Bamforth on one of the Brewstrong episodes (I think it was the haze stability episode) and he said something interesting. He said it's better to drop your beer to 29* for a day than 32* for a month, from a haze stability standpoint. Basically, you want to drop it as close to freezing as possible, without it actually freezing. Just FYI.


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Old 05-09-2011, 05:09 PM   #3
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Thanks. I hadn't heard what Charlie Bamforth said - interesting.
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Old 05-09-2011, 05:13 PM   #4
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For lagers, I'm a fan of gradually dropping the temp, 5 degrees per day until I'm at 34 degrees. I'm not sure about that yeast strain, as I've only used liquid lager yeasts, but lager yeast can stay active at lower temps than ale yeast strains. Cold crashing is more of an "ale thing".
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Old 05-09-2011, 05:15 PM   #5
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Here's the link to the episode:
http://thebrewingnetwork.com/shows/572
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Old 05-09-2011, 08:50 PM   #6
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Thanks. Anybody else have some advice?


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