Re: Fermentation won't start - HELP!

Fri Jan 03, 2014 10:46 am

LehighAce06 wrote:because of the half pound of dme used to make the starter.


Ah, I thought you were saying that the starter was increasing your gravity, rather than just not diluting it as much as water would have.

5 gal @ 1.097 = 485 total points - 20 points = 465 points

So the unknown gravity of your original 4 gal would have been 465/4 = 1.116 , and if you'd just topped up with water, you would have been at 465/5 = 1.093 instead of 1.096.
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Re: Fermentation won't start - HELP!

Fri Jan 03, 2014 11:03 am

that seems far too easy, but thanks! am i correct that a 0.5lb DME : 2L water starter is 1.040? i assume you got 20 points from 0.5gal (2L) x 1.040 gravity starter?

this would mean my gravity vs target is half because of the starter and half some other reason, perhaps over-lengthy steeping of specialty grains? regardless, i'm not going to worry too much about 7 points of gravity in something this high to begin with, as long as it ferments down as far as it should.
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Re: Fermentation won't start - HELP!

Fri Jan 03, 2014 8:37 pm

Most DME is rated at 44 pppg. That means if you dissolve 1 lb in 1 gallon, you'll get a wort of 1.044.
1 L is just a little more than 1 quart, so 2L is just a little more than half a gallon.
1/2 lb in a little more than 1/2 a gallon will come out a little less than 1.044, so close enough.
You REALLY don't know how many viable cells you have in your pack/vial, so honestly, you are talking about differences that fall way inside error levels.
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Re: Fermentation won't start - HELP!

Fri Jan 03, 2014 9:25 pm

awesome, that's all fairly simple to wrap my head around. i'm still curious why my gravity would've been 1.093 without the extra dme from the starter, rather than the projected 1.090, but i'm not going to worry too much about it at this point, i'm just glad my fermentation is chugging along (powerfully, by the way) ... i only hope it gets down as far as it's supposed to, and without too much on the ester side since i'm in the upper 60's degF.
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Re: Fermentation won't start - HELP!

Fri Jan 03, 2014 11:04 pm

LehighAce06 wrote: i'm still curious why my gravity would've been 1.093 without the extra dme from the starter, rather than the projected 1.090,


What efficiency was the recipe based on? Simple answer is that you got a higher efficiency than what it expected you to do. If this is repeatable across multiple batches, that is likely an indication that you and your system/process are more efficient, and you can tweak your recipe to be more in line with what you are really getting.

Among other things:

Crush
Temperature
Runoff
Ratio
Alignment of the moon
Whether you were wearing no pants or just :nutters:
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Re: Fermentation won't start - HELP!

Fri Jan 03, 2014 11:09 pm

I doubt I'm more efficient than suggested since I'm just starting, and I brew extract so no variance in mash process. I'm going to go with alignment of the moon, or maybe not wearing pants.
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Re: Fermentation won't start - HELP!

Sat Jan 04, 2014 10:44 am

LehighAce06 wrote:I doubt I'm more efficient than suggested since I'm just starting, and I brew extract so no variance in mash process.


In that case it is either a flaw in the recipe/calculation, or a mis-measurement of either the volume or the gravity (ie hydrometer calibration). It isn't that far off, you'd only be off by ~0.003 if we subtract the contribution from your starter (since it was only going for 4 hrs). This could be as simple as your volume being a pint under where you intended.
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Re: Fermentation won't start - HELP!

Sat Jan 04, 2014 11:05 am

In addition to what spider said, another common cause of "missed" gravity in extract batches is topping up and taking a gravity reading without thoroughly mixing the water into the wort. Then, you grab a small sample from either a concentrated part or a watery part and bingo, weird OG numbers. Even letting the wort sit a little can allow it to "layer" and if you draw your sample off the top it measures low or if you draw it off the bottom with a thief it measures high.

1.090 vs 1.093 is probably just a volume measurement thing, though.
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