my first lager

[size14]

after growing weary of ales i finally got up the gumption to try a lager. I brewed a bock from extract, lots of lme only one once of hops at the begining. After pitching the safe lager S34/70 I put the fermenter into a barrel of cool water on the basement floor, scared it was still to warm 60+ i moved the fermenter to a refrigerator and set it at the warmest setting, it is fluctuating between 40 and 50 degrees. The airlock has been going like a heartbeat for five days now, looks like it is starting to slow a bit.
I know this is happening at colder than normal temps but it looks like it is happening,, whats the downside,,my experience thus far with homebrew( all ales) is don't rush it. any and all input welcome.
On another point, the instructions that came with this kit say once all the foam is gone go ahead and proceed to bottling, what about a diactyl rest and lagering at a colder temp in a secondary????

 

[Cybershadow]

Do the rest for 3 days at room temp when fermentation is done then lager for at least 6 weeks below 40 degrees. That is what I do.

 

[EvilBrewer]

Ideally, you want to keep fermentation temperatures constant and within the appropriate range. Sounds like you're doing okay with the latter. With that yeast strain, keeping it in the 50's is best but if you're seeing activity in the airlock then it might be okay. You may or may not get off flavors, but if you do then revisit my first sentence. It solved many of my "flavor" problems.

As for diacetyl rest and lagering..I agree with Cybershadow. Three days at room temp to let the yeast clean up after themselves and then drop back down to 35ish degrees for a few weeks.

I'm not sure about bottling with lagers; I keg my beer and force carbonate. You need to make sure that there is enough yeast left in suspension to consume the priming sugar and carbonate your beer in the bottles. I've heard that lagering for too long can drop too much yeast out of suspension but I'm not sure how to define "too long". Might not be of concern but I'd check it out.

 

[menschmaschine]

Most lager yeast, including the popular strain of Weihenstephan's 34/70, will ferment down to around 42°F. For most lager yeasts, the only downside to fermenting colder than the optimal range is time. However, a very few are reported to produce off-flavors at lower temps. I don't believe W-34/70 is one of these. What does matter is how long it was allowed to lag/ferment at higher temps. This can produce diacetyl, esters, etc.

The ideal diacetyl rest is done before fermentation is complete... anywhere from 75% to 85% complete is good. This is when the yeast have consumed much of the readily available sugars and are looking for other compounds to metabolize, including diacetyl (which they produced earlier in fermentation), but before they go dormant. 10°F above your primary fermentation temperature is typical, but regardless of your primary fermentation temp, a 60°F D-rest is good. Diacetyl (and other "off-flavor" compounds) production also depends on how much yeast you pitched. A bock would probably need at least 3 packs of W-34/70. So, if you pitched less than that... all the more reason to do a good diacetyl rest.

If you have the means to lager in a secondary vessel, that is ideal (bulk lagering creates a more consistent final product). But you can lager in the bottles if you have to. Just bottle with priming sugar and let them carb for a few weeks (I would keep this carb-ing temp not far of above the optimal fermentation temp range for the yeast... like in the mid to upper 50s°F). Then lager near freezing for a week for every 8 points of OG... so a bock would probably need around 8 weeks.