# if you add the whole starter?

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#### bailey mountain brewer

##### Supporting Member
HBT Supporter
So here is my scenario.. 15gal batch so i am for 16.5 in the fermenter when i plan on a big dry hop, i build a 4000ml starter using all the typical calculators to get proper yeast cells .. thats simple. now say i came up a little short on my volume in the fermenter and rather then lose the volume i have basically a gallon of wort in the starter. so if im at 16gal of 1.074 wort and want to had half of the total starter instead of decanting off the entire thing to bring up my volume is there a way to factor that into my gravity readings to get a more accurate ABV? so 16gal at 1.074 + .5gal of 1.010 = 16.5gal of 1.0??? sure i could pull a sample after the starter is mixed in and before fermentation kicks off but i guess im looking to find a number before it happens so i can decide which i prefer, the abv loss or the volume loss.

#### KeizerBrewr

##### Pot stirrer
HBT Supporter
That is a very large, complex question. How many steps did you need to get the starter to hit your pitching rate? If you wanted to, your last step could be the morning of brew day, so only a few hours goes by before pitching and that will be something you can pitch in it's entirety. I'm sure roughly just over a gallon of mostly consumed starter wort going into 15 or so gallons won't hardly effect the OG, by maybe a few points at most. I am interested in this as well. Anyway, that is my .02.

#### Vale71

##### Well-Known Member
((16.5*1.074)+(0.5*1.010))/(16.5+0.5)=1.072

Edit: fixed mistake, one gallon starter instead of half gallon

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OP

#### bailey mountain brewer

##### Supporting Member
HBT Supporter
thanks @Vale71 that is exactly what i was looking for. for some reason i was struggling with the math on it but this explains it perfectly.

#### Vale71

##### Well-Known Member
Density is weight divided by volume. You add all the weights (which you get to by multiplying partial density by partial volume) and then divide by the total volume (which is simply the sum of all partial volumes).

OP

HBT Supporter
Got it

#### Vale71

##### Well-Known Member
By the way, in my opinion you're quite underpitched at that density and batch size but that's another issue.

OP

#### bailey mountain brewer

##### Supporting Member
HBT Supporter
it was a hypothetical ... dont have any exact numbers with me. i typically build up a couple times if im starting with new packs i use imperial yeast cause they start you with what they say is 200billion.

#### Gnomebrewer

##### Well-Known Member
((16.5*1.074)+(0.5*1.010))/(16.5+0.5)=1.072
This tells you the actual SG at the time of pitching, but a more relevant number for OG would use 1.040 as the gravity of the starter wort (or whatever the OG was of your starter). The starter already has alcohol when it's pitched; using it's FG as the gravity in your beers OG calculation won't ever account for the alcohol in the starter.

OP

#### bailey mountain brewer

##### Supporting Member
HBT Supporter
my typical process is to start with 1pack of 200billion cells, say its a month old or so, so about 156billion and build a 2L starter on the stir plate with 1.040 wort. this should give me 454billion i use that and pitch into a second 4l starter of 1.040 wort and back on the stir plate. this hits about 1050billion which should be plenty for my 16gal of 1.074

#### marc1

##### Well-Known Member
If you're doing this for ABV calculation purposes, you would also need to take into account the alcohol in the starter

OP

#### bailey mountain brewer

##### Supporting Member
HBT Supporter
right, and to be honest i couldnt tell you the last time i actually checked my gravity of the starter. again if you assume i start at 1.040 and it drops to 1.010 thats 3.9-4ish abv. but i dont have any clue if thats where they finish at for me maybe lower maybe higher but probably close.

#### Vale71

##### Well-Known Member
Just use the OG of the starter in the formula (if you haven't measured it you can just calculate it if it's a DME starter as there is no extraction efficiency involved) to calculate the beer's OG. It will be kind of a "virtual" OG as the starter has already fermented out and the measured OG wouldn't match this calculated OG. You'll basically be calculating the OG your wort would have had if you had dumped the same amount of unfermented starter wort in it before pitching. You can then use this calculated OG value plus the beer's measured FG value to calculate the ABV using the usual formulas/online calculators.

#### IslandLizard

##### Progressive Brewing
Staff member
Mod
my typical process is to start with 1pack of 200billion cells, say its a month old or so, so about 156billion and build a 2L starter on the stir plate with 1.040 wort. this should give me 454billion i use that and pitch into a second 4l starter of 1.040 wort and back on the stir plate. this hits about 1050billion which should be plenty for my 16gal of 1.074
A 5 liter 1.037-1.040 starter should give you your 816 billion cells (plus some extra) in a single step:
BrewUnited's Yeast Calculator

If you often brew 16 gallon batches, maybe use 2 stir plates, with 3 or 4 liter flasks.

#### jtgoral

##### Active Member
1,010 already has alcohol in it, one has to use starter's OG (1,035) in calculations. BTW, why anybody cares? Does it taste different?

In BeerSmith I just add starter's DME to the recipe and the software takes care of the calculations

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#### Beermeister32

##### Supporting Member
HBT Supporter
Starters have oxidized starter beer in them so I typically chill and decant the yeast slurry rather than pitching all the liquid - Just trying to reduce oxidized beer flavors wherever possible.

#### IslandLizard

##### Progressive Brewing
Staff member
Mod
Starters have oxidized starter beer in them so I typically chill and decant the yeast slurry rather than pitching all the liquid - Just trying to reduce oxidized beer flavors wherever possible.
That's the preferred way, indeed, and that's what many of us do.
But, from what I've read, adding as much as 10% oxidized starter beer  (adding ~2 liters of starter beer to ~20 liters of a batch of wort) [/Edit] doesn't seem to taint a batch enough to be noticed, apparently.

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OP

#### bailey mountain brewer

##### Supporting Member
HBT Supporter
Typically I do chill and decant. This was a what if scenario for me as I was curious how it would affect the final outcome. All these responses are great, I appreciate all the input, thanks all.

Cheers

#### jtgoral

##### Active Member
One adds yeast to the starter, yeast eats oxygen to multiply and once there is no oxygen it starts to eat sugar producing alcohol and CO2. CO2 fill all space above the fluid preventing air to touch the wort. So please somebody explains to me when the starter gets oxidized....

#### Vale71

##### Well-Known Member
CO2 fill all space above the fluid preventing air to touch the wort.
This is not what happens in reality, especially in agitated starters. Even in non-agitated starters air and CO2 will mix, as discussed countless times (sometimes to no avail) in this forum.

OP

#### bailey mountain brewer

##### Supporting Member
HBT Supporter
Yes I agree that starter wort is oxidized, I set my stir plate to run for 12 hours then just let it sit at room temp before eventually moving it to the fridge. Then on brew day I decant off and only pitch the yeast and enough liquid to swirl it off the bottom. It the past I have come up just a little short on volume which isn't a big deal, talking half a gallon in a 15 gallon final batch. So i was thinking i could just leave a half gallon in my starter and dump that in to top it off. This would not be my entire starter size as it it usually a little over a gallon. Does this amount result in oxidation to the final product? Or just lower my abv?

#### jtgoral

##### Active Member
This is not what happens in reality, especially in agitated starters. Even in non-agitated starters air and CO2 will mix, as discussed countless times (sometimes to no avail) in this forum.
I use an airlock when doing starter. I thought CO2 pushes all air out and no air comes back in.