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 Home Brew Forums > Starters and OG Calculation Question

05-30-2008, 07:46 PM   #1
polamalu43
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 Would a 2L 1.040 starter decrease the OG of a 1.070 wort?

Let’s say you’re making a somewhat big beer (OG above 1.070), and you want to make a starter. You make a two liter starter the day before and pitch the entire thing into your wort.

Wouldn’t this mean that whatever gravity that you took just prior to pitching would be slightly high?

In other words, if there are roughly 19 liters in a five gallon batch, and you draw your sample for an OG hydrometer reading from those 19 gallons, wouldn’t that reading change after adding 2 liters of starter (w/ an OG of 1.040)? The more dilute, 1.040 starter (2 liters) would mix with the 1.070 brew (19 liters), resulting in an OG lower than 1.070, right?

If so, how does one get a fully accurate OG reading when using two liter starters? Would you simply average it out? (i.e. [1.040*2 + 1.070*19] / 2 = 1.068).

I realize that this may be a bit technical, and that the effect of adding two liters of 1.040 liquid to 19 liters of 1.070 liquid might not drop the OG that much. Nevertheless, I was wondering what you all thought.

Thanks.

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Last edited by polamalu43; 06-03-2008 at 07:23 PM.

07-02-2008, 05:06 PM   #2
Alamo_Beer
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Have you checked out mrmalty.com and the starter guidlines over there? Theres also a cool pitching calculator that could help you

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07-02-2008, 05:12 PM   #3
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Quote:
 Originally Posted by polamalu43 Let’s say you’re making a somewhat big beer (OG above 1.070), and you want to make a starter. You make a two liter starter the day before and pitch the entire thing into your wort. Wouldn’t this mean that whatever gravity that you took just prior to pitching would be slightly high? In other words, if there are roughly 19 liters in a five gallon batch, and you draw your sample for an OG hydrometer reading from those 19 gallons, wouldn’t that reading change after adding 2 liters of starter (w/ an OG of 1.040)? The more dilute, 1.040 starter (2 liters) would mix with the 1.070 brew (19 liters), resulting in an OG lower than 1.070, right? If so, how does one get a fully accurate OG reading when using two liter starters? Would you simply average it out? (i.e. [1.040*2 + 1.070*19] / 2 = 1.068). I realize that this may be a bit technical, and that the effect of adding two liters of 1.040 liquid to 19 liters of 1.070 liquid might not drop the OG that much. Nevertheless, I was wondering what you all thought. Thanks.
Well, my thought is that it wouldn't affect the OG at all. I mean, the OG is the OG. You're not adding 1.040 wort to it- your starter should have fermented out, so you're actually adding some yeast slurry and beer. The beer will only ferment to the FG that the attenuation would allow. So, assume your starter DID start at 1.040- but finished at 1.012. You're simply adding 2 liters of yeast slurry and 4% ABV beer. So, if your recipe is actually for 1.070 beer, and the FG is 1.012, that is a 9% ABV beer. So, you added 2 liters of 4% beer to 5 gallons of 9% beer. That really is not very significant.
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