Starter Doubling

[ShaunG]

OK so in reading up on starters (for lagers in particular) I'm seeing the progression but missing the math on proper doubling.

If I make a starter and crash it then siphon off the old wort, make new oxygenated wort and pitch it, do I get the same rate of growth? The calculators I've looked at have 1st phase growth at double or so but the 2nd pitching doesn't produce nearly so much.

For my 15gal batches, should I just skip to the end and make a 6 Liter starter as a single generation?

[NateBrews]

For the size of batches you are talking about, you are going to need much more than a single 6L starter. To do it in a single step, you would need to grow 2 smack packs in a 16L+ starter on a stir plate and let that grow up.

At that point, why not grow up a batch of yeast for a smaller beer, a couple 2L steps or something on a stir plate pitched into a helles or pilsner at 1.045. Let that ferment out and harvest the yeast from that and use that to pitch into your bigger batch (though I'm still not sure that you would have enough yeast at that point for a 15g batch of something around 1.055). At least that way you get another batch of beer out of it rather than just making 4-5 gallons of wort and throwing it away.

[brewinhard]

For the size of batches you are talking about, you are going to need much more than a single 6L starter. To do it in a single step, you would need to grow 2 smack packs in a 16L+ starter on a stir plate and let that grow up.

At that point, why not grow up a batch of yeast for a smaller beer, a couple 2L steps or something on a stir plate pitched into a helles or pilsner at 1.045. Let that ferment out and harvest the yeast from that and use that to pitch into your bigger batch (though I'm still not sure that you would have enough yeast at that point for a 15g batch of something around 1.055). At least that way you get another batch of beer out of it rather than just making 4-5 gallons of wort and throwing it away.

+1.

[gwk453]

For lagers my batch size is 13 gallons / two 6.5 gal acid carboys.
I start with 2 fresh packs (I won't buy lager yeast over 45 days old)
My LHBS usually has very UGLY dates on their lager yeast, so I buy from a larger volume dealer and have it shipped.
Experiment to find out who can get you the fresh yeast overnight with just ground shipping.
I make 3 step starters on two separate stir plates, at the same time, one flask per yeast pack, with/ 1/8 teaspoon nutrient & 5 drops of Fermcap for the 1 & 2 l. flask, 10 drops for the 3 l. at 65 F.
1 l. for 48 hr.
2 l. for 48 hr.
3 l. for 48 hr.

Then chill to settle, rack off or decant brew day, draw 1000 ml./ 3 l. flask off the boil pot and chill to pitching temp, add back to each of the 3 l. flask, and put on the stir plate to oxygenate and activate the yeast prior to pitching.

I don't rack off from one step to the next, too much diddling can lead to contamination in my opinion. I would rather just Star San my flasks.
The first step is about 900 ml, so when I move to the 2 l., I just prepare ~ 800 ml. of water with the full weight of DME for a 2 l. starter which would be 200 grams, boil 6 min.
So when you add the original 1 L. flask to the 2 L. flask, it wont over fill.
And you do the same when going from 2 - 3 l. taking into consideration of the volume ~ 800 ml. with 300 g. of DME.
I end up with at least 1/2 in. of yeast on the bottom of the 3 l. flask

Using Tasty's fermentation schedule, I have had blow outs, with very little activity after 6 days.
Yes it is time consuming, but as Nate said you need a lot of vigorous yeast to ferment lagers.
I would rather spend my money on the extra DME and watch it grow than buying more yeast.
(My LHBS has only one or two packs 95 % of the time) You also do not know how the yeast was handled temp wise!
It may well be dead in the pack when you pitch it! So I grow it to see what I got. I too have bought dead lager yeast.
I have a separate temp controlled fridge just for lagers, pils, and bocks.
Spending about a week with yeast prep is a grind, but it has a positive effect on what goes in your glass.

Gary