From the HBD Archive
From: Pete Soper <soper@encore.com>
Subject: Color computing
Date: 1989-09-14 21:27:31 GMT

Mike Fertsch recently described how to predict the color
of a beer by adding up the color contribution of ingredients
using their Lovibond numbers. I would like to add a couple of
details to this based on my experience. I've been working on
a spreadsheet for quite some time that among other things
does color prediction. I've had to add to it to compensate
for a few important factors.
First, wort darkens while you are making and boiling it.
The amount of darkening can vary over a broad range. If you
do full wort boil with a heating system that doesn't burn
the wort then a fudge factor of around 25% might be right.
That is, the color of the wort might come out 1.25 times as
dark as what you would expect by just using the Lovibond numbers.
For a very long and/or very concentrated boil (e.g. not
boiling all the water with the extract), on an electric stove
with the kind of pot that is prone to hot spots, the fudge
factor needed to account for this could be dramatically higher.
In addition to the boil, I believe that handling of hot wort
while making it from grain can also cause darkening, especially
the transfer from the lauter tun. However I have not tried to
quantify this.
The wort lightens in color during fermentation. However the
amount of lightening is so slight that I ignore it. For that
matter, if you had the equipment to filter the yeast out of
your beer you'd probably want to take that into account since
other material is filtered out too and this can affect the
color. I recently visited a brewpub in England where the
brewmaster was moaning about having to deal with this kind of
tradeoff. He had a starch haze, but in getting rid of it he
lost significant flavor. But enough of that.
The very dark malts can produce color contributions
that are hard to predict. The way you grind, steep and sparge
them makes a big difference in the amount of color contributed.
For example I sampled a club beer last night that had a color
of about 13 degrees L which is roughly half way between Bass
Ale (10) and Michelob Classic Dark (17). As I'm looking at
this beer I'm being told that its maker intended it to be a
Porter and included 8 ounces of black patent malt. Huh?
A quick bit of pencil work tells me this beer should be
around 50-60 degrees L, which is essentially black. A few
moments later the club member says "I just cracked the black
malt with a rolling pin". Mystery solved.
By contrast I very finely grind the small amounts of chocolate
malt I use for color adjustments and get the "expected" color
contribution. So my current bias is to grind the heck out of
dark malts as part of extracting all the color. However this
might be the WRONG thing to do if you do not have a
filter bed of some sort to prevent the solid material from
getting into your boiling pot. In this case, you'd perhaps be
better off crushing the grain and applying a fudge factor
of less than 1 based on experience.
Haze is another thing that you have to account for. If you
are making a very pale beer the slightest bit of haze will make
the beer appear noticably darker. Darker beers are also subject
to this but it takes a lot more haze to swing the apparent color.
A few months back I got a couple of cylinders and some
Michelob Classic Dark and followed the procedure that Breiss
developed and Fix described in "Zymurgy" 9 months to a year
ago. It works very well and is super for determining the real
effects of different dark malts depending upon how you use them.
So let me just run through a quick example to tie this together.
I recently made a 5 gallon batch with these ingredients:

7 pounds (normally crushed) 2 row 1.2L Klages malt
1/2 oz finely powdered 350L chocolate malt
8 oz (normally crushed) 3L wheat malt
8 oz (normally crushed) 40L crystal malt

Here are the contributions:

7lb klages X 1.2 = 8.4
.031lb choc X 350 = 10.9
.5lb wheat = 1.5
.5lb crystal = 20

for a total of 40.8

dividing by 5 gallons gives an expected color of 8.2L

Then applying a fudge factor of 1.25 for wort darkening, 1.0 for
the dark malt grind and 1.0 for haze gives me 10.3L and
this is about what the beer really looks like and what I was
after in the first place. If I had put the chocolate malt
under a rolling pin I might have only gotten 1/3 the normal color
out of it and so would have gotten 8.3L. Applying a .33 fudge
factor would have led me to use 1.5oz and so compensate.
Likewise, a longer or more concentrated boil (i.e. not boiling
all the water with the extract) might have given me twice the
darkening or a fudge factor of 1.5 so I'd want to use less
chocolate to tune the final color.

--Pete

----------------------------------------------------------------------
Pete Soper +1 919 481 3730
internet: soper@encore.com uucp: {bu-cs,decvax,gould}!encore!soper
Encore Computer Corp, 901 Kildaire Farm Rd, bldg D, Cary, NC 27511 USA

Back New Search

The posts that comprise the Homebrew Digest Searchable Archive remain the property of their authors.
This search system is copyright © 2008 Scott Alfter; all rights reserved.