Hi there gpupu
I've been lazy on answering questions the last few weeks so let me have a crack at this for you. (There are some hard concepts below so don't worry if it doesn't sink in straight away).
The first problem you have is that it's very hard to tell in most recipes you stumble across, what they actually mean when they give you a volume. For example, a brewer might say, I made 20.82 litres of beer but you have no idea if they produced 20.82 litres into bottles, 20.82 litres of wort into their fermenter, 20.82 litres in their kettle after chilling or even 20.82 litres at the end of the boil. It's a big problem when you are trying to copy a recipe.
The volume figure you really want to know, is the volume they had at the end of the boil after they had cooled it ("Volume of Ambient Wort (VAW). Let's say, that the brewer you were copying from did actually have 20.82 L of ambient wort. From Section K in your file, we can see that you are producing 14.17 L of ambient wort. As your question so rightly says, "Why am I needing more ingredients?"
Here's what is happening...
First, I am going to remove all your numbers in Section W. (see the file I have attached below.) You will notice the following occurs...
1. VAW changes from 14.17 L to 18.67 L. (Original recipe is 20.82 L)
2. Grain Bill needed drops from 4926 to 4178 grams (Original recipe is 5482 grams)
3. Hop Bill drops from 184.3 grams to 152.4 grams (Original recipe is 169.9 grams)
Notice now how things are now balancing? For example, 18.67 / 20.82 X 169.9 = 152.4
Forget about the rind - that is an error in Section F of BIABacus PR1.3T
- The formula is back the front. For example, on your orange zest, it is going 20.82 / 18.67 * 28 instead of 18.67 / 20.82 * 28 so proper amount to add would be 25.1 grams.
Okay, that makes sense so why are my additions in Section W Making Such a Difference?
There are two numbers in Section W that are resulting in the "apparent" discrepancy. They are the "Water Added During the Boil" and "Water Added to Fermenter".
Any dilution water you add is water that can't be used to wash the grain. This means you can't get the grain as clean. This results in a vicious cycle where you have to add more grain to get the amount of sugar you need from it for your brew. In your original file, you needed 4926 grams of grain versus 4178 grams of grain. If you exaggerate this concept into something easier to get your head around, imagine...
...if you put a tea bag in a mug and only filled the mug up a quarter, let it soak, pulled it and then topped up the mug. You are going to get weak tea. If you insist on using that method, to get the right strength tea, you might have to use two tea bags.
Okay, I get that but there must be something else?
Diluting in the fermenter, not only has the above effect, it also has one more. At the end of the boil, you end up with a much higher percentage of debris/trub than if you were not diluting in the fermenter. This higher percentage of trub means that the hop oils have more "crap" to stick to instead of going into your beer so, like the grain, you need to use more hops to compensate for this.
Putting It All Together
Any time you make a full volume variation in Section W, it will always cost you in either extra equipment, work, mess, quality and/or ingredients.
Have a read of this article
to work out how to get the right balance from the kettle size you have.
*The concepts I've explained above can take a while to get your head around so don't be worried if it doesn't sink in after just one read of the above and the article. Let us know though if some bits are still confusing once you've had a ponder over the above with a beer.
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