[gmac]

I'm brewing today and I'm going to pitch a healthy starter of Wyeast 2112.  Last time I brewed, I saved the last 3 litres of my sparged wort for use in a starter.  The OG of this is pretty weak about 1.020. 
I was thinking of doing the following and wondered what you thought or what you suggested.
Once I pitch the starter, I was going to add 1L of boiled and cooled sparged wort to the container that my starter is in.  My intent is to try to culture the remnants back up to a pitchable quantity which I will then wash and store in the fridge for a future batch or pitch right away if necessary (I intend to do another batch before the current one is done).

I've asked about this before and people have said this would work but my question for the day is:  Is 1.020 too low?  I have 2 more liters that I was going to add in a few days to keep building up the population but should I up the OG of that?  Would 3 L of 1.020 be enough?  If not I have some DME I can add to bring it up when I boil it but I wondered if starting off at 1.020 was OK. 
Not that DME is expensive but I figured if this will work, why not.
Thanks

[denny]

1.020 is great.  That's about what they yeast companies use.

[gmac]

So should I just put in all 3 liters now then?  Is there any reason to do it in increments?

[Hokerer]

So should I just put in all 3 liters now then?  Is there any reason to do it in increments?

Isn't the general rule that you don't want to step up more than an 8:1 ratio?

[denny]

So should I just put in all 3 liters now then?  Is there any reason to do it in increments?

Isn't the general rule that you don't want to step up more than an 8:1 ratio?

I usually hear 10:1 as the ROT.

Graham, I'm a but confused...when you say "Pitch the starter" do you mean the smack pack?  I often pitch an Activator pack into 3 qt. of wort.  They may not have enough cells for 5 gal. of beer, but they certainly have plenty for 3 qt. of starter wort.

[tschmidlin]

5 to 10:1 is a loose rule of thumb, but it's hard to say what that means in this context.  You'd have to add wort until you had the cells in a solution at a density ~ the same as the starter had, then multiply that out by whatever ratio to figure out how much to add.

But if your starters are anything like mine in terms of how much gets left behind in the flask, adding a liter should be fine, and step it up from there.

Ultimately though, I don't know if 3 liters of 1.020 will get you enough yeast for a pitchable quantity, it depends on how much you're starting with and what you plan to pitch it in.  But you'll be ahead of the game, and can always add more steps until you have enough slurry.

[a10t2]

1.020 is great.  That's about what they yeast companies use.

Do you mean 1.002? I was under the impression they use sequential wort additions to keep the gravity below the Pasteur limit, while also oxygenating. All reproduction, no fermentation.

[denny]

1.020 is great.  That's about what they yeast companies use.

Do you mean 1.002? I was under the impression they use sequential wort additions to keep the gravity below the Pasteur limit, while also oxygenating. All reproduction, no fermentation.

I recall being told 1.020.  But I could be wrong.

[gmac]

Denny - about a week ago I pitched the smack pack into 3L of 1.040 starter.  I meant to brew earlier but work keeps getting in the way.  A couple days ago I put it in the cold room and now I have a nice thick creamy layer of yeast that I'm going to pitch today.  I'm looking to step up what is left in the bottom of the jug as Tom commented on.

So, I have no idea how much that will be in terms of ratios.  It's just what's left over clinging to the sides and bottom of the jug.  Based on the past, I'd guess maybe a teaspoon of slurry if it all ran together.  I could also leave a touch more and not wait for it all to run out. 

a10t2 - I measured the OG of the last 3 liters from the last batch sparge.  It was 1.020.  This is the final runnings (and I added a bit more water to get this) so I think it's pretty close to right. 

I have no means of oxygenating the beer beyond the intermittent shake method.  I was sort of thinking along the lines that Tom was about whether this would be enough but I can step it up more.  That's why I was wondering about adding 1L today and then fortifying the other 2 liters to get a bit more growth.

[gmac]

1.020 is great.  That's about what they yeast companies use.

Do you mean 1.002? I was under the impression they use sequential wort additions to keep the gravity below the Pasteur limit, while also oxygenating. All reproduction, no fermentation.

I recall being told 1.020.  But I could be wrong.

a10t2 - sorry, I see now you were replying to Denny, not me.  Thought you were implying my readings were wrong - which they could be...

Tom, the intent would be to pitch into another 5 gal batch at approximately 1.056-1.058 OG.  My effiency isn't 100% repeatable yet.

[Hokerer]

So, I have no idea how much that will be in terms of ratios.  It's just what's left over clinging to the sides and bottom of the jug.  Based on the past, I'd guess maybe a teaspoon of slurry if it all ran together.  I could also leave a touch more and not wait for it all to run out. 

With just a "teaspoon'ish" amount, you might want to keep your first step even lower than 1L - maybe 1/4 to 1/2 and then later on toss in the rest of that first liter along with the second and third liters for your second step.

[tschmidlin]

So, I have no idea how much that will be in terms of ratios.  It's just what's left over clinging to the sides and bottom of the jug.  Based on the past, I'd guess maybe a teaspoon of slurry if it all ran together.  I could also leave a touch more and not wait for it all to run out. 

With just a "teaspoon'ish" amount, you might want to keep your first step even lower than 1L - maybe 1/4 to 1/2 and then later on toss in the rest of that first liter along with the second and third liters for your second step.

I think a tsp of slurry is fine into a liter.  A white labs tube has what, maybe 50 mls of slurry?  That's only about 10 tsp and can be pitched directly into 19 liters of 1.040 wort.  Given the low (1.020) gravity of the starter wort, a tsp should be plenty of cells.

I don't know if you'll have enough yeast though, you'll have to eyeball it if you're not going to do cell counts.  Use the mrmalty calculator and estimate the slurry density, that should get you in the ballpark.  If you wanted to add a little DME to the 2nd two liters I think that would be fine, but I think I would only add about 100 grams or maybe less.

[gmac]

After all that, I overfilled the carboy so I have about 1/4 cup of slurry left over anyway.  I've added 1L of 1.020 to about 1/4 cup of slurry.  Should be enough yeast in that to get me going.  I'll spike the next addition with 100 g of DME. 
I must admit, I'm worried about contaminating the yeast.  Not sure how I would have but I must admit it concerns me.  How do you guys check if you've contaminated your starter?  I've just been smelling mine and if it smells nice and yeasty with no discernable vinegar or anything, in it goes.  I considered tasting the liquid I pour off but haven't.