How to calc ABV if you add more sugar - Home Brew Forums

 Home Brew Forums > How to calc ABV if you add more sugar

01-14-2009, 01:07 AM   #1
sandman24
Recipes

Jan 2009
Austin, Tx
Posts: 26

Okay, so Ive read some recipes where you add additional sugars i.e. brown sugar, maple syrup, molasses... to the primary after so many days of fermentation. My question is how in the world do your figure out your ABV if your gravity readings are always changing?? Do you take a reading every time you add sugar? Is there a magic equation that I haven't read yet?
Thanks!

01-14-2009, 01:29 AM   #2
dontman

Recipes

Oct 2008
Philly, PA
Posts: 2,402
Liked 27 Times on 22 Posts

Yes there is a measurable amount of fermentable sugars to each item. i.e. cane sugar = 42 GU per lb. in a 5 gallon batch you divide the 42 by 5 = 8.4 = add 1.0084 to your OG.
__________________
On Tap: 1. Kelly R. IPA, 2. Roter Hund Hefeweizen, 3. Bud Killer Blonde, 4. Red Dog Pale, 5. Roter Hund Oktoberfest, 6. Pumpkin Ale, 7. McRed's Stout (with new nitro system and stout tap,) Cream Soda, 8. ESB # 3, & 9. Ordinary Bitter.

01-14-2009, 03:00 AM   #3
sandman24
Recipes

Jan 2009
Austin, Tx
Posts: 26

Is there a easier way to find the gravity unit of fermentable sugars for a noob??

Thanks

01-14-2009, 03:03 AM   #4
ArcaneXor

Recipes

Nov 2007
Posts: 4,572
Liked 118 Times on 105 Posts

Quote:
 Originally Posted by sandman24 Is there a easier way to find the gravity unit of fermentable sugars for a noob?? Thanks
By looking at this table and going by the third (or fourth) column:

http://www.howtobrew.com/section2/chapter12-4-1.html

http://www.northernbrewer.com/sugars.html also lists a couple, and brewing software such as Strangebrew Java 2.01 has a database of all sorts of ingredients that you can look up, add to a recipe, and calculate the resulting gravity.

01-14-2009, 05:17 AM   #5
Shawn Hargreaves
Recipes

Jun 2008
Seattle
Posts: 344
Liked 5 Times on 4 Posts

By far the easiest way is to enter this data into a brewing program like Beer Smith. Refined sugars have totally consistent and known fermentability, so its predictions will be very accurate for something like this.

Adding sugar is different to the original mash, where the software estimate can be thrown off by differences in your mash efficiency. But as long as you take a reading after the initial mash and boil, you can use that to calculate your efficiency and get the software set up right, after which it will accurately tell you the effect of adding extra sugars.