From the HBD Archive
From: hpfcla!hpcea!hplabs!rutgers!!akelei!crispy!dwight (Dwight Melcher)
Subject: What is your extract efficiency?
Date: 1989-02-06 22:08:52 GMT

Hi everybody,

I have a question for those who do all-grain brewing:

What is your typical extract efficiency?

"Why do I ask?" you say to yourself. Well, I've been all-grain brewing
for some time now with great success. I find the extra effort worth
the improvements in the brew (not to mention the extra control over the
final product.) There is only one area that I'm still not sure
about. It seems that my extract efficiency is always lower than most
books say it should be. Before I go any further, here is my
understanding of "extract efficiency".

Extract efficiency is the weight of sugar you actually extract
from a known weight of grain divided by the theoretical maximum
weight of sugar possible to extract from the grain.

To clarify, say you have some Klages pale malt. One can look in a
brewing book to find the laboratory maximum extract yield per pound of
grain of various types. Pale malt, for example, can yield 65-70% (that
is, 1# of grain can give you .65-.7# of sugar). Now, this is the
amount of sugar you would expect to get if your mashing/sparging etc. is 100%
efficient. So, one way to calculate extract efficiency is:

S = pounds of sugar you end up with in your primary fermenter

G = sum(pounds_of_grain[i] * lab_max_yield_const[i])

efficiency = S / G

Getting S is as simple as knowing the SG and volume of your wort before
you pitch. I know Noonan's book has a table listing the #/gal sugar
for a variety specific gravities. The CRC handbook of Chem. and Phys.
does too. There are a number of other ways to calculate extract
efficiency, involving division of SG's (make sure all the volumes are
the same!) but for brevity, I won't go into them.

So, the crux of the question is this: most books seem to imply that
ones extract efficiency should be in the 80-90% range, while my extract
efficiency is always around 70%.

Here are some general areas that probably affect ones extract efficiency
and my humble observations about my techniques:

* Grain Grinding - I use a Corona mill. Perhaps I'm not grinding the
grains finely enough? From what I've seen of other grists, my grind
appears OK.

* Mashing: I always get a negative iodine test within 15-30 minutes of
reaching saccharification temperatures, so I'm confident conversion
is complete before I sparge.

* Sparging: I suspect this may have the greatest influence on the final
extract efficiency. My sparging technique follows Noonan's
book reasonably closely, and my lauter-tun is a "zapap" style
(that is, two 5 gallon buckets, one inside the other).
Any hints or tips in this area would be appreciated.

* Boiling, etc. : the usual. The stuff one does after sparging
doesn't have much impact on extract efficiency anyway.

So, if everybody else is getting extract efficiencies in the 70% range,
I'll just relax and assume these other sources are a little off.
Otherwise, I'd be interested in hearing your techniques that lead to
a higher extract efficiency.

Dwight Melcher

ps. Now, don't get the idea I'm a white-knuckle homebrewer or anything.
I'm quite relaxed about brewing, so suggestions to the effect "add more
grain to compensate", or "boil down to bring the gravity up", or "relax",
are less interesting than a discussion of the topic :-).

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