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 Home Brew Forums > low attenuation

11-30-2012, 11:37 PM   #11
TheBeerist
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How much yeast did you pitch? My calculations indicate that you would have needed 3 vials without a starter for a 1.080 beer. This could easily be the culprit.

What's the FG of your belgian trippel going to be? 1 vial for a starter may not be enough. 2 definitely will be. If you go with 1 vial, you're going to need a decent sized starter, 3-4L. 2 vials, a 2L starter should suffice.

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12-01-2012, 12:46 AM   #12
mccartney
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so if i take my OG 1.082 and convert it to brix, it would be 20.5, and convert my Current gravity of 1.037 to 9.25. if i put it into the calculator it says i have a current gravity of 1.007. if thats the case and i use the formula of
1.082 - 1.007 * 131 i have an abv of 9.825 % ? and that would mean i have attenuation of 91.4 %. is my math right?

im confused how the calculator makes my current gravity much lower

i havent thought ahead to the trippel yet but id hope the FG would be around 1.02 or so
how do you calculate how much yeast you need for the original gravity and the size of the starter?

Update: i just took a reading with a hydrometer and this being day 10 the reading is 1.025. so if i have 3 readings, one from a refractometer, one from a hydrometer, and one from an online calculator, why are they so drastically different? thats attenuation of 69.5% and abv of 7.467%. what do i trust?

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12-01-2012, 03:17 AM   #13
mgortel
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You trust your hydrometer reading......your refractometer is not wrong either....just that you have to perform the calculation correctly to get correct SG from brix conversion....once fermentation has begun....which is your case.

The refractometer reading is good for original gravity reading.....BEFORE there is any alcohol in it. Refractometer is calibrated for WATER with no alcohol...its just the way it works.

Once the beer has started to ferment and you have alcohol in there it will throw the refractometer readings off....that is why you need to use the calculator.

So you take a refractometeer reading before fermentation begins.... for your OG....in brix...and do the straightforward conversion to OG....which you said was 1.084

Now that it is 10 days later.....if you use refractometer...you are now getting a reading of a liquid with water and alcohol...so if you convert that to SG with your normal conversion (4 x brix or whatever it is....) you will get an incorrect value.

you the correct SG...

For the Norther Brewer Calculator link someone posted.....
Under "Brix to Gravity during and after fermentation converter"

Enter "20.5" for Original Brix
Enter whatever your current brix reading is in "Current Brix" and calculator will give you correct SG.

So if your current SG based on hydrometer is 1.025 I suspect your Brix reading with refractometer should be around 12.0

So it looks like you are at around 70% attenuation right now......

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12-01-2012, 03:48 AM   #14
mccartney
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ok this is great! i think despite not making a starter its actually going to turn out well. im glad to know that the real problem was the instruments i was using. if i have 70% att and its still slightly bubbling, maybe ill get it to 75 in a couple days. maybe think about secondary soon.
i hope i didnt get any infection opening the lid several times to get readings, but every time i did i used sanitizer on everything, so ill just pray no oxidization.
thanks to everyone for helping me with this problem

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12-01-2012, 04:24 AM   #15
mccartney
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so when thebeerist says for a 1.08 SG brew i need a 3 to 4 liter starter, is it really true i am going to add another whole gallon to my wort? does that mean i boil my wort down to 4 gallons to make a 5 gal batch? wouldnt that change the SG?

also while were talking about fermenting, this belgian trippel kit i ordered said estimated OG is around 1.076 ish. lets say hypothetically i made a decent starter, good aeration, even oxygenation. when the ferment starts slowing down, lets say i add 2 lbs of table sugar in a sterile solution. will that shock the yeast or will it start fermenting again? what repercussions would i face?

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12-01-2012, 11:01 AM   #16
WoodlandBrew
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As long as the alcohol level doesn't go above the level the yeast can take adding sugar after fermentation has slowed is what I would recommend. It will be less stressful on the yeast that way because the osmotic pressure is lower.

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12-01-2012, 01:33 PM   #17
mgortel
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You will not add all of the liquid you use to make the starter.

After your starter is complete....you will place it in the fridge and let the yeast settle to the bottom of the flask....give it like a day....then you will have all of the liquid setting above the yeast...then you decant the liquid out (just a fancy word for carefully pouring most of the liquid out without dumping the yeast)...but you have to leave a little liquid to suspend the yeast in. Remember you will need a day for each litre of starter you plan on.....so if doing a 2 litre starter you will need to start this at least 2 days ahead of brew day....I usually give it an extra day in case the yeast is slow to start.

Then you let it warm to room temp.....give it a good swirl to suspend the yeast in the remaining liquid...and pitch them suckers into your brew. SO you may be adding a pint or so of liquid.

Do a search on Fermentation and Yeast forum....you will find all kinds of information...it is quit easy....most important part as usual....sanitation!

Check out this link to Northern Brewer Yeast Starter kit....there is a good video on upper right of screen on how to do a starter

http://www.northernbrewer.com/shop/2000-ml-yeast-starter-kit.html

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12-04-2012, 08:56 PM   #18
mccartney
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ok so another question about adding sugar. if i do add a lb or 2 when the fermentation is dying down, how do i adjust the SG or atleast a certain gravity to compare the final gravity to for calculating attenuation and abv?

does that make sense?

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12-04-2012, 09:48 PM   #19
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Quote:
 Originally Posted by mccartney ok so another question about adding sugar. if i do add a lb or 2 when the fermentation is dying down, how do i adjust the SG or atleast a certain gravity to compare the final gravity to for calculating attenuation and abv? does that make sense?
Just add it to the OG that you measured.
x = number of pounds added
b = batch size (5 gallons)
43 = pppg for sugar
OG = original gravity that you measured before pitching.

OG + (x * 43 ) / b

So for a 5 gallon batch of 1.080 with two lbs of sugar the new FG is:

80 + (2 * 43) / 5 = 97.2 or a specific gravity of 1.097

Use the same FG that you originally calculated because sugar will ferment out nearly 100%.
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12-04-2012, 09:50 PM   #20
mccartney
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should i just pour the sugar in the wort or boil it in some water and cool first? and do i aerate or oxygenate again too?

also i dont remember how fermentable maltose is but im going to guess 75%. would that mean i would adjust the formula for adding malt as
og + (((x*43)/b)*.75) ?

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