Author Topic: Need help with RIS gravity  (Read 739 times)

Offline Jeff

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Need help with RIS gravity
« on: July 07, 2017, 06:16:20 PM »
I need help with estimating the current gravity of my RIS.  It's been in primary for four weeks.  The SG was 25.8 brix or 1.109.  The current brix reading is 15.  Plugging these numbers into the various online resources has given me FG's of anywhere from 1.030 - 1.050, and ABV's from 9-11.  I'm wanting to bottle this, but want to verify attenuation.

Offline 69franx

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Re: Need help with RIS gravity
« Reply #1 on: July 07, 2017, 06:38:30 PM »
Is your gravity stable? Have you taken multiple readings over a number of days? This is the only real way to know if it is done. Also, with your numbers in °Brix, it seems you may be using a refractometer for your readings. If so, you do need to use a calculator to estimate SG, and may also require starting readings with both hydrometer and refractometer.
Frank L.
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In the works: Hopefully brewing 10 gallons of Pilsner tomorrow for a family reunion in July, then back to IPA and  a barleywine to age

Big Monk

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Need help with RIS gravity
« Reply #2 on: July 07, 2017, 06:41:56 PM »
I need help with estimating the current gravity of my RIS.  It's been in primary for four weeks.  The SG was 25.8 brix or 1.109.  The current brix reading is 15.  Plugging these numbers into the various online resources has given me FG's of anywhere from 1.030 - 1.050, and ABV's from 9-11.  I'm wanting to bottle this, but want to verify attenuation.

My calcs show 1.038 and 62.9% AA. What was your FG goal? Did you run a FFT?

Offline Jeff

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Re: Need help with RIS gravity
« Reply #3 on: July 07, 2017, 06:42:18 PM »
When I plug 25.8 brix into calculator, it gives me an estimated SG of 1.109.  This is how I've been calculating my SG's.  Is there another step I'm unaware of?

Big Monk

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Re: Need help with RIS gravity
« Reply #4 on: July 07, 2017, 06:43:51 PM »
When I plug 25.8 brix into calculator, it gives me an estimated SG of 1.109.  This is how I've been calculating my SG's.  Is there another step I'm unaware of?

Are you talking °Bx or °P?

1.109 S.G. = 25.7 °P = 26.7 °Bx

Offline 69franx

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Re: Need help with RIS gravity
« Reply #5 on: July 07, 2017, 06:44:15 PM »
Also, what did your grist look like? High levels of unfermentables from caramel or roasted malts will yield a higher FG. And to answer the last question, yes. If you are only using the refractometer, it will give a skewed result due to the presence of alcohol. The calculator will be based off of starting hydro and refract readings. I am sure someone will post a link to Sean Terrill's online calculator
Frank L.
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In the works: Hopefully brewing 10 gallons of Pilsner tomorrow for a family reunion in July, then back to IPA and  a barleywine to age

Offline Jeff

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Re: Need help with RIS gravity
« Reply #6 on: July 07, 2017, 06:48:32 PM »
Refractometers measure brix right?  It read 25.8 post boil.  I estimated that as 1.109 SG which may have been wrong.  The current measurement on the refractometer is 15 which has held for almost two weeks.

Offline 69franx

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Re: Need help with RIS gravity
« Reply #7 on: July 07, 2017, 06:51:39 PM »
That current reading is skewed due to the alcohol present, while the SG was not skewed (no alcohol yet) the calculator from Sean will use a wort correction factor based on starting gravity to give a better estimate of actual final gravity.
Try this link:
http://seanterrill.com/2012/01/06/refractometer-calculator/
Frank L.
Fermenting:
Conditioning:
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In the works: Hopefully brewing 10 gallons of Pilsner tomorrow for a family reunion in July, then back to IPA and  a barleywine to age

Offline 69franx

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Re: Need help with RIS gravity
« Reply #8 on: July 07, 2017, 06:53:01 PM »
His default wort correction factor of 1.040 is generally a good place to start if you dont know your exact WCF, Big Monk can likely explain obtaining that number a little better than I can
« Last Edit: July 07, 2017, 06:58:25 PM by 69franx »
Frank L.
Fermenting:
Conditioning:
In keg:
In Bottles:  
In the works: Hopefully brewing 10 gallons of Pilsner tomorrow for a family reunion in July, then back to IPA and  a barleywine to age

Big Monk

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Need help with RIS gravity
« Reply #9 on: July 07, 2017, 06:55:01 PM »
Using Sean's calcs, which I have in my own personal calculator:

Your OG was actually 1.105 S.G.

Your current gravity is 1.042 S.G. corrected for alcohol.

That leaves you with a subpar 57.7 % AA. What yeast did you use? Recipe?


Sent from my iPhone using Tapatalk Pro
« Last Edit: July 07, 2017, 07:01:05 PM by Big Monk »

Offline Jeff

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Re: Need help with RIS gravity
« Reply #10 on: July 07, 2017, 06:58:28 PM »
That calculator gives me an FG of 1.042 and ABV of 7.9%.  Other calculators have given me FG's of 1.030 and ABV's over 10%.  It definitely tastes like it's way over 8%.  I'll have to post the recipe later.  It had a ton of grain...I think it was 48 lbs of grain in 10 gallons, and a ton of chocolate and roasted grains.

Offline 69franx

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Re: Need help with RIS gravity
« Reply #11 on: July 07, 2017, 07:00:22 PM »
I used the calculator and got the same results as Big Monk. As he stated, more info on your recipe, yeast, and fermentation schedule can better help us to help you
Frank L.
Fermenting:
Conditioning:
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In the works: Hopefully brewing 10 gallons of Pilsner tomorrow for a family reunion in July, then back to IPA and  a barleywine to age

Offline 69franx

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Re: Need help with RIS gravity
« Reply #12 on: July 07, 2017, 07:01:42 PM »
That ton of chocolate and roasted grains will not yield the same fermentability as your base malts and will tend to yield a higher FG. Post the recipe specs when you can and everyone can help trouble shoot it for you
Frank L.
Fermenting:
Conditioning:
In keg:
In Bottles:  
In the works: Hopefully brewing 10 gallons of Pilsner tomorrow for a family reunion in July, then back to IPA and  a barleywine to age

Offline Jeff

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Re: Need help with RIS gravity
« Reply #13 on: July 07, 2017, 07:03:19 PM »
Also, I used WLP001 slurry from a ten gallon cream ale.  I'm certain I didn't underpitch.  Beersmith says it needed 800 billion cells.

Offline 69franx

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Re: Need help with RIS gravity
« Reply #14 on: July 07, 2017, 07:07:19 PM »
I would say it was a grist issue just off the top of my head based on my experiences with WLP001, regularly getting 78-82% attenuation rather than the 57% you have, although I have not used it in that big of a beer before.
Frank L.
Fermenting:
Conditioning:
In keg:
In Bottles:  
In the works: Hopefully brewing 10 gallons of Pilsner tomorrow for a family reunion in July, then back to IPA and  a barleywine to age