Author Topic: Calculating fermented sugar  (Read 1013 times)

Offline muddypuddle

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Calculating fermented sugar
« on: March 14, 2011, 01:37:29 PM »
i brewed a huger beer- 1.128 og into primary. after 5 days, it was down to 1.054 and I added ~2lbs of dark candi syrup (1.032 gravity each). week later it was down to 1.020 and i added ~2 more pounds of the dark syrup. 5 more days and it is back down to 1.020.

anyone got an equation to determine total gravity/fermented sugar?

i am planning on transferring to 2ndary on Wednesday or thursday.

thanks-

Phil

Offline tschmidlin

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Re: Calculating fermented sugar
« Reply #1 on: March 14, 2011, 02:24:10 PM »
If you know your volume and you know the SG of the dark candi syrup you can figure it out.  It's going to be something like:

(Vi*SGi+Vs*SGs)/(Vi+Vs)=SGt

Where V is volume, SG is expressed in points, subscript s is syrup, subscript i is initial, subscript t is total.  It will get you close, but it won't be exact because Vi + Vs != Vt
Tom Schmidlin

Offline muddypuddle

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Re: Calculating fermented sugar
« Reply #2 on: March 15, 2011, 10:44:15 AM »
If you know your volume and you know the SG of the dark candi syrup you can figure it out.  It's going to be something like:

(Vi*SGi+Vs*SGs)/(Vi+Vs)=SGt

Where V is volume, SG is expressed in points, subscript s is syrup, subscript i is initial, subscript t is total.  It will get you close, but it won't be exact because Vi + Vs != Vt

ok let me work this out online so all can see my inferior math skills!

one thing i am confused on is Vs.  is that volume of syrup?  not sure how to calculate that as it is 4# of syrup at 1.032/pound.  but i'll give it a go.

(6.5*1.128 +4*1.032)/(6.5+4)=
(7.332+4.128)/10.5=
11.46/10.5=
1.091 = SGt

is that right?

Offline tschmidlin

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Re: Calculating fermented sugar
« Reply #3 on: March 15, 2011, 11:58:02 AM »
No, you can't substitute pounds for gallons, and also the gravity of the syrup is probably not 1.032, that is probably the potential SG.  The way you've got it the gravity dropped when you addded syrup :)  If the potential SG of the syrup is 1.032, that's per pound in one gallon of water - you can estimate that 1 lbs of syrup is 1/12 of a gallon, based on honey weighing about 12 lbs per gallon.  This gives us an estimated gravity of 1.384, which is a bit less than the SG of honey.  4 lbs is about 1/3 gallon, so it becomes:

(6.5*128 +(1/3)*384)/(6.5+.33)=
(832+128)/6.83=
960/6.83=140.6

So you can estimate your OG was 1.141

There's a lot of estimates in there though.
Tom Schmidlin

Offline muddypuddle

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Re: Calculating fermented sugar
« Reply #4 on: March 15, 2011, 12:35:11 PM »
No, you can't substitute pounds for gallons, and also the gravity of the syrup is probably not 1.032, that is probably the potential SG.  The way you've got it the gravity dropped when you addded syrup :)  If the potential SG of the syrup is 1.032, that's per pound in one gallon of water - you can estimate that 1 lbs of syrup is 1/12 of a gallon, based on honey weighing about 12 lbs per gallon.  This gives us an estimated gravity of 1.384, which is a bit less than the SG of honey.  4 lbs is about 1/3 gallon, so it becomes:

(6.5*128 +(1/3)*384)/(6.5+.33)=
(832+128)/6.83=
960/6.83=140.6

So you can estimate your OG was 1.141

There's a lot of estimates in there though.


yeah, thanks dude.  i knew it would bean esitimate and it actually is not that far off of just calculating gravity as if you put the syrup in the boil. i think that was calculated at 1.135 or 38.

thanks for your time

Offline tschmidlin

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Re: Calculating fermented sugar
« Reply #5 on: March 15, 2011, 03:01:47 PM »
Good point, it should be really close, especially if you calculate it for the higher total volume.
Tom Schmidlin