Step feeding and working out ABV

[Jack_0106]

Quick one for you guys, bit of a newbie here,

I have a gallon straight apple cider going at the moment. OG was 1.050 and after a week it was down 1.004 giving me a rough ABV of 6%. I've added 7oz of white sugar to boost the ABV. From what I've read, that should equate to about an extra 2% abv in a gallon.

Does anybody know:

1 - Is that correct?
2 - Is there a formula/equation for working out how many gravity points a certain mount of sugar would add? For example, if I had my FG at 1.000 and wanted to raise it to 1.020? (In a gallon)
3 - How do you work out final ABV after step feeding?

Cheers,

Jack

 

[hottpeper13]

The sugar I use is pure cane juice sugar and that has a 46 GU per gal. so 7 oz is a little less then half so maybe 20 GU's. If it finishes at 1.000 then 20 x .132 = 2.64 abv.

 

[Jack_0106]

The sugar I use is pure cane juice sugar and that has a 46 GU per gal. so 7 oz is a little less then half so maybe 20 GU's. If it finishes at 1.000 then 20 x .132 = 2.64 abv.

Thanks Hottpeper - Can you work out ABV of step fed brews by doing this?

OG2 is gravity after adding sugars

(OG1 - FG1) + (OG2-FG2) * 131.25

 

[hottpeper13]

If you are always adding sugar it will ferment to 0 or .999,so FG will be that. In order to figure out ABV when done you need the amount of sugar added at each step and the total volume. I add sugar to the fermenter on most of my Belgian brews so the OG of the wort is 1.070,I add 2 lbs sugar and the volume is at 5.25 gal ,I've added 92 GU's to a 1.070 wort (even thou it's almost at FG) you divide the 96 by 5.25 = 17.5 add that to the 1.070 =1.087.5. This is the OG and then if you keep adding sugar it's GU contribution is added to OG-1. In my mind (witch sometimes is confused) there is only OG, and FG-1. Or maybe i should just sweep the broom!

 

[Jack_0106]

If you are always adding sugar it will ferment to 0 or .999,so FG will be that. In order to figure out ABV when done you need the amount of sugar added at each step and the total volume. I add sugar to the fermenter on most of my Belgian brews so the OG of the wort is 1.070,I add 2 lbs sugar and the volume is at 5.25 gal ,I've added 92 GU's to a 1.070 wort (even thou it's almost at FG) you divide the 96 by 5.25 = 17.5 add that to the 1.070 =1.087.5. This is the OG and then if you keep adding sugar it's GU contribution is added to OG-1. In my mind (witch sometimes is confused) there is only OG, and FG-1. Or maybe i should just sweep the broom!

Okay that seems pretty complicated...

I've two questions -

Where did the 96 come from?
Is there way of working out how many GU a measurement of sugar is in a gallon (for simplicity)?

 

[doug293cz]

Okay that seems pretty complicated...

I've two questions -

Where did the 96 come from?
Is there way of working out how many GU a measurement of sugar is in a gallon (for simplicity)?

I think the 96 was a typo, which should have been 92 (= 2 * 46)

46 (46.17 or 46.21 depending on who's value you believe) is the PPG of sucrose. This means if you mix 1 lb of sucrose with enough water (0.9261 gal) to make 1.00 gal of solution, the solution will have an SG of 1.046. Note that the sugar has an effective volume of 1.0000 - 0.9261 = 0.0739 gal.

Back to the 7 oz added to 1.0 gal of 1.050 cider: You originally started with 50 gravity points, and the sugar will add 46 * 7 / 16 = 20.125 more gravity points, and 0.0739 * 7 / 16 = 0.0323 gal of volume, so the new "effective" OG is:

New OG = 1 + 0.001 * (50 + 20.125) / (1.0 + 0.0323) = 1.0679 ~= 1.068​

​

So, you use 1.068 as your OG in the ABV calculation, and whatever your FG ends up at.

If we hadn't corrected for the added volume of the sugar, the new OG would have come out to:

New OG = 1 + 0.001 * (50 + 20.125) / 1.0 = 1.070​

​

This isn't a huge error, and you might be satisfied with the simpler calculation.

Brew on

 

[DuncB]

@VikeMan I think in another thread said that you could also calculate the alcohol with a method using both hydrometer and refractometer readings at the end of ferment. But I may be mistaken.
I'm keen to find out if this is possible as I chaptalised an imperial stout with about 2kg of dextrose and it will be ready to sample in a few months.

 

[Hoochin'Fool]

I whipped up a recipe in BrewersFriend, 17.3 oz cane sugar in 1 gal has OG of 1.050
If I add another 7 oz of cane sugar, OG goes up to 1.070, and if I then adjust batch size to 1.03, it goes to 1.068

(I originally did this in BrewTarget, and it says that the OG would be 1.062 -- didn't realize it was THAT buggy)

 

[DuncB]

Looks like I found the answer ( perhaps) here

https://www.musther.net/vinocalc.html
I'm not sure of the formula behind this.

scroll down to find this and put in the numbers
Alcohol from Hydrometer & Refractometer:

 

[VikeMan]

@VikeMan I think in another thread said that you could also calculate the alcohol with a method using both hydrometer and refractometer readings at the end of ferment. But I may be mistaken.
I'm keen to find out if this is possible as I chaptalised an imperial stout with about 2kg of dextrose and it will be ready to sample in a few months.

There are formulae for this. They are a sort of estimates on top of estimates kind of thing. Here's one:
https://www.vinolab.hr/calculator/alcohol-from-hydrometer-refractometer-en27
But in your case, if you knew the OG of the stout without the sugar, you could pop that into the FruitCalc spreadsheet, along with your Sugar Addition (select "Corn Sugar" from the "fruit" dropdown) and get a calculated effective combined OG.

FruitCalc Download

 

[DuncB]

There are formulae for this. They are a sort of estimates on top of estimates kind of thing. Here's one:
https://www.vinolab.hr/calculator/alcohol-from-hydrometer-refractometer-en27
But in your case, if you knew the OG of the stout without the sugar, you could pop that into the FruitCalc spreadsheet, along with your Sugar Addition (select "Corn Sugar" from the "fruit" dropdown) and get a calculated effective combined OG.

FruitCalc Download

Thank you I'll use both methods and see what numbers I get. The Vinolab looks similar to the Vinocalc one I found.

I used dextrose powder as my addition the corn sugar is related to the powdered not syrup values?

 

[VikeMan]

I used dextrose powder as my addition the corn sugar is related to the powdered not syrup values?

Yes, the one that says "Sugar (Corn Sugar)" in FruitCalc is the powder, i.e. Dextrose, aka Glucose, aka Corn Sugar.

 

[Jack_0106]

I think the 96 was a typo, which should have been 92 (= 2 * 46)

46 (46.17 or 46.21 depending on who's value you believe) is the PPG of sucrose. This means if you mix 1 lb of sucrose with enough water (0.9261 gal) to make 1.00 gal of solution, the solution will have an SG of 1.046. Note that the sugar has an effective volume of 1.0000 - 0.9261 = 0.0739 gal.

Back to the 7 oz added to 1.0 gal of 1.050 cider: You originally started with 50 gravity points, and the sugar will add 46 * 7 / 16 = 20.125 more gravity points, and 0.0739 * 7 / 16 = 0.0323 gal of volume, so the new "effective" OG is:

New OG = 1 + 0.001 * (50 + 20.125) / (1.0 + 0.0323) = 1.0679 ~= 1.068​

​

So, you use 1.068 as your OG in the ABV calculation, and whatever your FG ends up at.

If we hadn't corrected for the added volume of the sugar, the new OG would have come out to:

New OG = 1 + 0.001 * (50 + 20.125) / 1.0 = 1.070​

​

This isn't a huge error, and you might be satisfied with the simpler calculation.

Brew on

Thanks a mill Doug!