First lager - yeast performance question

MVKTR2 said:

I've got a Munich Dunkel fermenting right now. Fermentation is slow and steady with wlp820 (known to be finicky but mine is moving right along). Temp varies due to swamp cooler method but staying in the 50s.

Yeast pitched monday.
Active fermentation began Wednesday.
It is now Friday.

Question: I am doing a diacetyl rest toward the end of fermentation. How do I know I'm reaching the end of fermentation as this is a fairly slow fermentation with 1 bubble every 4.6 seconds consistently for 2 days now. Is it going to slow quickly or gradually?

Ultimately I guess I should ask if I slip up allowing active fermentation to end, will a diacetyl rest be effective if I raise the temp to 70 after active fermentation?

All this is important as I'm going out of town for the weekend to get some much needed R&R with the wife in control of putting ice bottles in the swamp cooler.

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MVKTR2 said:

Thanks TheMadKing

Well that's disappointing ... from 1.055 to 1.050 in 54+ hours of active fermentation. On the bright side it tastes very clean!

I guess another way of asking this is:
If an average active fermentation stage of average strength american style ales is 3-4 days(when proper quantities of yeast are pitched), how long should an average strength lager take to ferment with proper quantities of yeast pitched?

No matter what I've got my answer thanks to gravity reading I know swmbo will be keeping watch over fermentation while I'm gone! She'll hate this but marriage is about sacrifice(her) and kissing up(me) ... oh and love... almost forgot that one!

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MVKTR2 said:

Weird, just very WEIRD!
I'm 9 days into primary fermentation and am at 1.040, roughly 40% of expected attenuation. This is wlp820 which is generally described as the most finicky lager yeast on the market. It is fermenting away, a dark brown not too high krauzen on top with 1 bubble consistently every 3.1 seconds for days. Temp consistent in mid 50s.

I had an older vial of yeast that I pitched into 400 ml of 1.028 starter. It fermented out then added 500 ml of 1.040 wort. Decanted, poured in 1 liter of 1.040 wort, fermented out. Decanted, poured in 2 liters of 1.044 wort. Decanted, pitched in 5.5 gal batch.

That's a total of 3.9 L of starter, the yeast was very healthy.

Any thoughts?

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TheMadKing said:

You probably didn't get much growth in your starter until your last step, unless your yeast vial had about 1 billion viable cells in it.

1L or less for a starter doesn't result in much growth from a wlp vial or smack pack. You were basically just waking the yeast up, feeding them, and putting them back to sleep without making any new cells.

Unless your viability was 1%.. You mentioned it was an older vial.

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MVKTR2 said:

I believe the expiration was early/mid November and I undertook making the starter in Jan. I remember viability being below 25% so maybe my dates are wrong. The 400 then 500 ml steps were necessary to get it going. It went like gang busters at room temperature on both the 1L & 2L steps.

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Yooper said:

Just checking- you're not using a refractometer to measure the SG, right? Using a hydrometer?

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