First wort gravity calculation
Can someone post the calculation for first wort gravity calculation.
First Wort Gravity Calculation
I am not aware of any calculations for determining the gravity of first wort. You have one equation and two unknowns. You're unknowns are the amount of malt you use and your brewhouse efficiency for the duration of the first wort runnings. Unfortunately as the grain quantity changes so does the brewhouse efficiency. Without a correlation between the two you can't predict what you will get. The composition and integrity of the grain bed and the physical characteristics of the malt are also variable and will determine the rate at which the extract is leached out of the lauter tun.
If anybody has a different opinion please feel free to post.
Kunze gives a general rule stating that the first wort gravity is 20 Plato when 100 kg malt is mashed with 3 hl water and then uses a ratio relationship to determine the mash thickness for a desired first wort gravity.
For example, if you want a first wort gravity of 24 Plato and want to calculate mash thickness Kunze suggests that the following is true:
Mash thickness = (3 hl water/100 kg malt)(20 Plato)/(24 Plato)
Mash thickness = 2.5 hl water per 100 kg malt
This can obviously be rearranged to caluclate first wort gravity from a given mash thickness. For example, if you use a 3.2 hl water/100 kg malt ratio you can caluclate first wort gravity by:
First wort gravity = (3 hl/100 kg malt)(20 Plato)/(3.2 hl/100 kg malt)
First wort gravity = 18.75 Plato
These calculations come pretty close to what I see in our brewery. I am not sure what Cargill's comment about brewhouse efficiency has to do with your question about first wort gravity. It does seem to me that the Kunze equation is based on typical malt and probably applies to a very narrow range of raw materials ... this probably works for most German beer styles.
Paul Mueller Company / Springfield Brewing Company