unwashed yeast, slurry from prior batch?

I have a good quantity of saflager34/70 slurry in the fridge from a batch I transferred out of my fermenter 2 weeks ago. I would like to use this tonight to brew another lager, but have no experience pitching prior slurry. The OG of both batches will be approximately the same, and I have about 0.5L of slurry to work with. How much to use for 5.5L batch?

mrmalty yeast calc will tell you

Okay, i'll play. Bought the Mr. Malty app for my phone. I've got the basics entered into the calculator. What yeast concentration should I enter? Default seems to be 2.4billion/ml. will this work out?

Read the simple yeast storage sticky at the top of the board. It should help with your assumptions.

Ok. So approx 386ml of slurry, I'm guessing one HEAPING cup-scoop (250+ml) and a few Tbsp will do???

Whats the OG of the lager?

Natdavis777 said:

Whats the OG of the lager?

Click to expand...

The actual OG is yet to be determined. I expect 1.055 but could go either way. I'm about 13 mins to flameout at this moment. I'll update in real time if possible, I would rather not ruin a batch from over/under pitching after a 90 min mash, and 90 min boil.

One of my first batches I had a plan to get some yeast from a local brewery. I took my quart jar down there, put my name on it and waited. About two days later I got a call that my jar was ready. The very inexperienced brewery assistant said 'just pitch the whole quart'. About 2 weeks later I met up with the brewer who asked how many batches I was planning with that quart jar. Well, out of inexperience I said 'just the one batch!'. He laughed, said I only needed about 1/2 cup of it...but you know what, that milk stout turned out fantastic even with a healthy over-pitch. Now I'm not telling you to throw in the whole thing, but I bet you wouldn't notice the difference if you did.

Seriously. I'm probably going to decant the "beer" layer and swirl it up. Anything light enough to make it onto the fermenter will go on to make the beer. I'm not actually expecting a perfect result. Is the general consensus that a slight overpitch is preferable to underpitching on a small batch such as this?

I work with 1.2 billion cells per ml of compacted yeast, bc Im conservative like that. But I think you will be fine with 386 billion if that is what you have (opposed to the recommended 450+)... You are at least in the ball park. Go with it. See how the beer turns out.

From all the posts I've read on this site, an assumed over-pitch is much more friendly to your beer than an under. I'm only 36 batches deep, but I read this site religiously and that is the consensus I've come away with. Also, unless you have a way to count the yeast in that slurry you're not guaranteed that you are over-pitching.

This is the formula I use for slurry:

Wort volume in liters x gravity in Plato = volume of slurry in ml.
Ex: 5.7 g @ 1.060 SG =
21.57 l x 15ºP = 323.5 ml
If you'd like: Ale x .75 Lager x 1.5

This is based on 1 billion cells/ml slurry, so it may be a bit conservative, but as was mentioned, better over than under, especially for lagers.

The under pitching or over pitching of yeast can manipulate the amount of yeast character you perceive in the finished beer. For beers with belgian yeasts, or Bavaraian Hefeweizen for example, that have a high amount of yeast driven flavors, its more critical than with "clean flavor" yeast such as 1056. Can you over pitch a clean lager yeast and detect a difference? I don't know, would be interesting to compare.