Manual calculation of FG with only knowing Lbs of each grain

[dn151864]

Hey everyone,

I'm reading the book Designing Great Beers. Currently on chapter 6 - hitting target gravity.

I'm brewing a beer this weekend that I received the ingredient list from the Brooklyn Brew Shop Beer Making Book. It's the Rye P. A.

Either way, I thought it'd be fun to run the calculations in the book using the ingredient list I have.

9lbs Maris otter malt
2lbs rye malt
. 8lbs caramel 60
.5lbs caramel 20

I looked up online, and found the extract potential of each of these maltsto be (respectively) 1.038, 1.029, 1.034, and 1.035.

I will be making a 5 gallon batch and I'm assuming I'll have a low efficiency of .68 (first time making a 5 gallon all grain batch) just to be conservative.

Now, I haven't gotten too far into the book but it seems like all of the examples he uses, he tells you the final gravity. I want to find my potential final gravity. Is that possible to do?

I'd like to manually calculate this out. Do you have any good resources to learn the equations and how and why the equations work?

Thanks!

 

[RedlegEd]

Hey everyone,

I'm reading the book Designing Great Beers. Currently on chapter 6 - hitting target gravity.

I'm brewing a beer this weekend that I received the ingredient list from the Brooklyn Brew Shop Beer Making Book. It's the Rye P. A.

Either way, I thought it'd be fun to run the calculations in the book using the ingredient list I have.

9lbs Maris otter malt
2lbs rye malt
. 8lbs caramel 60
.5lbs caramel 20

I looked up online, and found the extract potential of each of these maltsto be (respectively) 1.038, 1.029, 1.034, and 1.035.

I will be making a 5 gallon batch and I'm assuming I'll have a low efficiency of .68 (first time making a 5 gallon all grain batch) just to be conservative.

Now, I haven't gotten too far into the book but it seems like all of the examples he uses, he tells you the final gravity. I want to find my potential final gravity. Is that possible to do?

I'd like to manually calculate this out. Do you have any good resources to learn the equations and how and why the equations work?

Thanks!

Hi. This about as good as you can get. Ed

 

[ajdelange]

0.68 is probably a good place to start for an initial guess at conversion. Add up the weight of all the grains and multiply by 0.68. That tells you how much extract you are likely to get. Add to this the weight of the water you will add (as reduced by boiloff and increased by added sparge) and divide into the extract. One hundred times this i.e. 100*0.68*Grain_Wt/(0.68*Grain_Wt + Water_wt) is the OG of the wort in °P. Multiply this by 1 - ADF%/100 where ADF% is the anticipated apparent degree of fermentation (from the yeast spec). The result is the AE. Use the Balling formula to calculate ABW and ABV from this and Bob's your uncle.

 

[dn151864]

Thanks!
RedlegEd. Thank you for the link. If it's coming from John Palmer it's gotta be good!

ajdelange, one question about what you said. "Add to this the weight of the water you will add" should I add the total amount used, as in the amount used for the mash and the amount for sparging? Or just use the total amount that I want (5 gallons) at the end?

 

[ajdelange]

"Add to this the weight of the water you will add" should I add the total amount used, as in the amount used for the mash and the amount for sparging? Or just use the total amount that I want (5 gallons) at the end?

I'm afraid I used misleading wording there. The weight of the water that should be used here is the weight of the water that enters the fermenter that is the weight of the water used for mashing minus the weight retained by the grains plus the water added for sparge minus the amount lost in the boil and the amount evaporated in the fermenter. For planning these are things you must estimate.

to get an actual conversion efficiency numer measure the specific gravity of the wort, convert to density and multiply by the actual volume at 20 °C to get total mass. Now convert SG to Plato and multiply by °P/100 to get the mass of the extract. Divide that by the mass of the grains to get your conversion efficiency.