Ever find a great looking recipe - on a website, in a book, or elsewhere plug it into your brewing software - and the numbers just don't add up?
I'm specifically talking about the IBUs and the specific gravity.
It can be frustrating!
Here are the main reasons why that happens:
(Note: I've included screenshots from BeerSmith on where to look for these numbers. Any good brewing software will have these, however.)
1. Efficiency
Proper homebrew etiquette dictates that when you publish your recipe, you state your assumed efficiency. But a lot of brewers got bad manners!
Efficiency is the first place to look.
If you plug a recipe into your brewing software verbatim, and your gravity doesn't match up, it's likely because they assumed a different efficiency.
Of course, you can figure out the efficiency. You would need to enter their recipe, observe the original gravity, and tweak the efficiency until you hit their stated original gravity.
But that sure is a pain. So I'll say it again - for the good of homebrewers everywhere, state your efficiency!
Mash Efficiency
2. Extract Potential
This one is more elusive. Before I knew to look for this, I fumbled for hours trying to figure out why my numbers didn't match up.
My efficiency was correct. My volumes were spot on. My grain amounts matched exactly.
What was the problem? The extract potential in my brewing software was different than what the author assumed.
Just one point different, but it was enough to cause a discrepancy in the OG. The extract potential refers to fermentable sugar contributed by the grain.
We sometimes forget that in brewing we're dealing with living (or formerly living) things. Hops, malt, and yeast are not artificial ingredients made in a lab. That means they don't always behave predictably. Malt composition changes.
It's helpful to learn how to read a malt analysis sheet. Keep in mind that the extract is in reference to pure sugar (sucrose) which has a ppg (points/pound/gallon) of 46. The ppg is the number you want to focus on because it's the one you'll tweak in your brewing software.
I recommend getting familiar with certain types of grains. If you buy from a local homebrew store, use the same brand over and over again. Eventually you'll learn how it performs, not just in taste but in its extract yield.
This is an area where the art and science of homebrewing merge fun stuff.
Grain Potential
3. Alpha Acids
Alpha acids chemicals that contribute to the bitterness of the beer. Hops vary greatly in their alpha acid content depending on their variety. From the 3% A.A. Saaz hops to the 16% A.A. ultra potent Warrior hops.
But don't be fooled!
Just like the extract potential of malt changes, so does the alpha acid content of hops. Even within a single variety.
The default value for a particular hop in your brewing software is just that - a default value. Always edit that number to what is printed on the label of your hop package. That will ensure your IBUs match up.
Alpha Acid
4. Hop Formula
If your hop amounts, alpha acids, and volumes are correct and you're still not getting the right IBUs, then there's a good chance that you're using a different hop formula than the recipe author.
There are three main hop formulas: Tinseth, Raeger, and Gaeretz. Each will give you a slightly different IBU figure.
Most brewing software lets you easily switch between the formulas, so if your number is off, trying toggling through the formulas and see if you can get it to match up.
Personally, I use Tinseth and stick with that. There is no "correct" formula. It's more important to just pick one and be consistent in all your recipes.
Formula
5. Liquid volumes, especially "batch size"
Unfortunately there is no agreed upon definition of "batch size".
A few of the ways I've seen defined:
The reason is because this is where the composition of the wort gets locked in. Once you're done boiling, the gravity of the wort and the IBUs do not change.
As we know, boiling increases both the IBUs and gravity.
After the boil everyone has their own techniques: hopping, recirculating, whirlpooling, etc. If we all called "batch size" the volume at flameout it would cause less confusion.
Batch Volume
So there you have it. A few of the main reasons why your numbers may different from those in a published recipe. If I've saved someone from even a few minutes of frustration, I've done my job.
I'm specifically talking about the IBUs and the specific gravity.
It can be frustrating!
Here are the main reasons why that happens:
(Note: I've included screenshots from BeerSmith on where to look for these numbers. Any good brewing software will have these, however.)
1. Efficiency
Proper homebrew etiquette dictates that when you publish your recipe, you state your assumed efficiency. But a lot of brewers got bad manners!
Efficiency is the first place to look.
If you plug a recipe into your brewing software verbatim, and your gravity doesn't match up, it's likely because they assumed a different efficiency.
Of course, you can figure out the efficiency. You would need to enter their recipe, observe the original gravity, and tweak the efficiency until you hit their stated original gravity.
But that sure is a pain. So I'll say it again - for the good of homebrewers everywhere, state your efficiency!
Mash Efficiency
2. Extract Potential
This one is more elusive. Before I knew to look for this, I fumbled for hours trying to figure out why my numbers didn't match up.
My efficiency was correct. My volumes were spot on. My grain amounts matched exactly.
What was the problem? The extract potential in my brewing software was different than what the author assumed.
Just one point different, but it was enough to cause a discrepancy in the OG. The extract potential refers to fermentable sugar contributed by the grain.
We sometimes forget that in brewing we're dealing with living (or formerly living) things. Hops, malt, and yeast are not artificial ingredients made in a lab. That means they don't always behave predictably. Malt composition changes.
It's helpful to learn how to read a malt analysis sheet. Keep in mind that the extract is in reference to pure sugar (sucrose) which has a ppg (points/pound/gallon) of 46. The ppg is the number you want to focus on because it's the one you'll tweak in your brewing software.
I recommend getting familiar with certain types of grains. If you buy from a local homebrew store, use the same brand over and over again. Eventually you'll learn how it performs, not just in taste but in its extract yield.
This is an area where the art and science of homebrewing merge fun stuff.
Grain Potential
3. Alpha Acids
Alpha acids chemicals that contribute to the bitterness of the beer. Hops vary greatly in their alpha acid content depending on their variety. From the 3% A.A. Saaz hops to the 16% A.A. ultra potent Warrior hops.
But don't be fooled!
Just like the extract potential of malt changes, so does the alpha acid content of hops. Even within a single variety.
The default value for a particular hop in your brewing software is just that - a default value. Always edit that number to what is printed on the label of your hop package. That will ensure your IBUs match up.
Alpha Acid
4. Hop Formula
If your hop amounts, alpha acids, and volumes are correct and you're still not getting the right IBUs, then there's a good chance that you're using a different hop formula than the recipe author.
There are three main hop formulas: Tinseth, Raeger, and Gaeretz. Each will give you a slightly different IBU figure.
Most brewing software lets you easily switch between the formulas, so if your number is off, trying toggling through the formulas and see if you can get it to match up.
Personally, I use Tinseth and stick with that. There is no "correct" formula. It's more important to just pick one and be consistent in all your recipes.
Formula
5. Liquid volumes, especially "batch size"
Unfortunately there is no agreed upon definition of "batch size".
A few of the ways I've seen defined:
- Volume at flame out
- Volume into the fermentor
- Volume into bottles/kegs
The reason is because this is where the composition of the wort gets locked in. Once you're done boiling, the gravity of the wort and the IBUs do not change.
As we know, boiling increases both the IBUs and gravity.
After the boil everyone has their own techniques: hopping, recirculating, whirlpooling, etc. If we all called "batch size" the volume at flameout it would cause less confusion.
Batch Volume
So there you have it. A few of the main reasons why your numbers may different from those in a published recipe. If I've saved someone from even a few minutes of frustration, I've done my job.
