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HOMEBREW Digest #4903
HOMEBREW Digest #4903 Sun 04 December 2005
FORUM ON BEER, HOMEBREWING, AND RELATED ISSUES
Digest Janitor: pbabcock at hbd.org
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Contents:
re: Make it stooopppp!/hydrometers/more ("steve.alexander")
Re: Make it stooopppp!/hydrometers/more ("A.J deLange")
Refractometer use during and post-fermentation (Michael Owings)
Eating Hops ("Jay Spies")
hydrometer - Howto calibrate ? measurement temp! ("steve.alexander")
Northern Brewer Sponsors HBD For 2006! ("Pat Babcock")
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----------------------------------------------------------------------
Date: Sat, 03 Dec 2005 02:47:00 -0500
From: "steve.alexander" <-s at adelphia.net>
Subject: re: Make it stooopppp!/hydrometers/more
John Peed writes ...
>Steve, I don't understand why you want to monitor the fermentation
Ellen Parr sums it up, "The cure for boredom is curiosity. There is
no cure for curiosity".
>it seems a very invasive activity to me. I mean, one of the
>first things a neophyte brewer should be told [...]
I wasn't suggesting that an an*l probe of your fermenter was a
matter for neophytes.
>If I were trying to make a bajillion gallons of Budweiser every day
We've much more important work at hand ... we're trying to make 10
gallons of really good beer per month. Which would you rather have ?
This isn't about process control, but about knowing.
>A hydrometer alerts you to major discrepancies so you can
>correct them.
Baloney ! I'd wager that 92% of HBers take an SG reading and
50% take an FG reading and no-one (well maybe AJ) tests FG till it
either stops or sticks. The hydrometer merely confirms the
diagnosis - it's not predictive.
>So no offense, but please, stop splitting hydrometer points
It'll stop soon enough. Close your eyes till the wailing and
gnashing of teeth ceases.
- ---
AJ deLange writes ...
>[...] I never got #4897!
Neither did I !
>[...] I've got a couple of
>observations. First is, that as I have noted before, one must have a
>fairly good hydrometer (or preferably narrow range set of hydrometers)
I've got a pair of Ertco's and the first (1.000 -1.070, resolution 0.0005,
and same for accuracy (hah!)) has a calibration error very close to 1.75SG
degrees ! Someone had a BT article a few years back and they went through
half a dozen brewing hydrometers (from GW Kent I think) and all had serious
calibration errors.
>It is the position of the ASBC that readings "only slightly less precise"
>than [...] 0.000 08 for digital density meters.
Lessee, 0.080 SG degrees is less than atmospheric pressure variations will
cause on a hydrometer - so I'd say the ASBC guys were "slightly less than"
sober when they said that. If they meant 4 times less accurate is
"slightly" - OK, but that's pushing the point.
>Steve mentioned a lot of factors which bear on the workings of
>hydrometers.
Right - and part of my thinking is that there are many factors that impact
hydrometer readings in the 0.1SG degree range which are not
always accounted for by the HBer.
>A properly made hydrometer inserted in a sample at the
>proper temperature (ASBC wants attemperation to 0.1 C)
Oh come now AJ - surely you realize that's nonsense. A 0.1C difference
in temp results in roughly a 16ppm error in an SG reading. Normal
atmospheric pressure changes can cause several times that amount of error.
>Clearly with sugar content (Plato scale hydrometer) there is no issue
>with respect to apparent/true
Right - and a point well taken. It's useful and practical to convert to
Plato right off. Density and SG change w/ temp - Plato does not.
>With a specific gravity scale true/apparent isn't much of an issue
>[...] but
>there is a problem in entering the ASBC tables (20C/20C) with a
>hydrometer calibrated for some other reference [...].
...
>I was a little puzzled by Steve's comment about the Plato tables
>indicating thatthe SG of sucrose solutions do not change in proportion
>to pure water
Perhaps I didn't state it well, but that is the issue. I think it's
in one of Hardwick's books and the 60F (from memory) was probably not
Plato's digression, but adapted from ...?Balling? ... and interpolated
to 15.6C. Anyway the point is the two different tables don't match
the temp expansion of water. So you can't really convert wort SG
between temps using only the temp coefficients for water. Yet another
small source of error accumulation.
>I thought Steve's most interesting comment was about the potential for
>yeast to effect the hydrometer reading. As the hydrometer displaces
>yeast when it is lowered into the sample if the yeast have an effect it
>will be seen. Intuition says that as yeast are in suspension until they
>floc and then they either go up (top cropping) or down (bottom cropping)
>and take a fairly long time to do that they must have a density pretty
>close to that of beer. Furthermore, as a barrel of beer gives me only
>perhaps 600 ml of compacted yeast they are a small percentage (about
>0.5%) of the total volume and shouldn't have much effect.
1/ I believe you'll find that yeast have an SG a bit greater than even
heavy gravity wort, and merely ride CO2 for suspension and 'surfacing'.
Could be wronng but it seems reasonable.
2/ The differences in density doesn't have to be so very great. If your
0.5%(5000ppm) of yeast are only 10% more dense than the wort/beer then
the excess of about 500ppm gives a 0.5SG degree error ! We are measuring
small difference here and little things count. How long will to take
SG=1.1 yeast to settle in a SG sample tube ?
>I opined the other day that one ought to be able to easily acheive 0.2P
>accuracy
0.2P ~= 0.8SG degree just under 1SG degree -I agree that's about the level
where the going gets tough.
>with a hydrometer without taking too much care.
Right - but this means calibrating the hydrometer, controlling temperature
and degassing .... then of course reading correctly through the meniscus.
>I took a sample into a hydrometer jar [...] I put enough
>sample in the jar that the fluid displaced overflows the top (as the
>ASBC likes)
Funny but my hydrometer mfgr suggest sighting from below then bringing up
your field of vision the lower side of the liquid surface. They claim
their procedure is adapted from a NIST circular.
>I read 6.2P. Then [...] 6.33 P [...] Accuracy of better than 0.2P
>For precise work yeast should be removed.
Thanks, I appreciate the confirmation.
>Now as we are all good scientists
And I thought we were all "penny stox players" ...
>Finally let's observe that if we start with 10P wort and have a standard
>deviation of 0.1P in our hydrometer readings
Hold that thought AJ - what if the average HBer doesn't have a density
meter to calibrate against and is off by 0.2P or 0.3P ? Also they are
using a little $6 hydrometer where the meniscus 'blind spot' spans 2SG
degrees - 0.5P. My NIST referenced ERTCO has systematic error around 0.4P
so it's not unlikely. I certainly think 0.2P is do-able, but I don't think
it's quite so easy.
You seem to have both high resolution and very accurate hydrometers AJ
(is it 8P range, 0.2P resolution & accuracy ? Or have you calibrated these
?)-would you care to mention the type/vendor ?
-SteveA
------------------------------
Date: Sat, 03 Dec 2005 15:13:07 +0000
From: "A.J deLange" <ajdel at cox.net>
Subject: Re: Make it stooopppp!/hydrometers/more
steve.alexander wrote:
>
> I've got a pair of Ertco's and the first (1.000 -1.070, resolution
> 0.0005,
> and same for accuracy (hah!)) has a calibration error very close to
> 1.75SG
> degrees !
If you know you have a systematic error take it out!
> Lessee, 0.080 SG degrees is less than atmospheric pressure variations
> will
> cause on a hydrometer - so I'd say the ASBC guys were "slightly less
> than"
> sober when they said that. If they meant 4 times less accurate is
> "slightly" - OK, but that's pushing the point.
>
Don't think I agree with that. The length of the stem out of the liquid
depends on the atmospheric pressure through a term (1 -
air_density/fluid_density) in the denominator which means that it's
approximately equal to hf + hf*air density. where hf is how high it
would stand if air density weren't a factor. At 29" Hg air density is
.001170 and at 31" it is .001250 a change of .0001 so that if mid scale
on my hydrometer represents 5 cm extension I might expect a difference
of .0005 cm in stem height between the midst of the summer Bermuda high
and the eye of Katrina. As my stem is calibrated for about 1 cm per
degree Plato that amounts to .0005P (.000 002 SG) change due to a 3 or
4 sigma swing in atmospheric pressure. I'm sure the ASBC guys tipple at
their meetings (never been to one) but before a MOA is published it is
very thoroughly considered and subject to collaborative experiment.
>
>> A properly made hydrometer inserted in a sample at the proper
>> temperature (ASBC wants attemperation to 0.1 C)
>
>
> Oh come now AJ - surely you realize that's nonsense. A 0.1C difference
> in temp results in roughly a 16ppm error in an SG reading. Normal
> atmospheric pressure changes can cause several times that amount of
> error.
>
Well yes on the first part (about 16 ppm but not about being nonsense)
and thats why they want 0.1 degree attemperation. 16 ppm means 1.000016.
They talk about .00008 inter laboratory or 80 ppm. 16 ppm seems an
appropriate allocation to temperature error (but remember the 80 ppm is
for electronic meters which hold temperature to a millidegree). As I
showed above the atmospheric changes are not a factor.
>
> Perhaps I didn't state it well, but that is the issue. I think it's
> in one of Hardwick's books and the 60F (from memory) was probably not
> Plato's digression, but adapted from ...?Balling? ... and interpolated
> to 15.6C. Anyway the point is the two different tables don't match
> the temp expansion of water. So you can't really convert wort SG
> between temps using only the temp coefficients for water. Yet another
> small source of error accumulation.
As I recall the whole point of the Normaleichungskomission was to deal
with known errors in the Balling tables. These were mostly in the 5th
and 6th decimal places. Another fine point to consider is that the ITS
(International Temperature Scale) has been revised.
> 2/ The differences in density doesn't have to be so very great. If your
> 0.5%(5000ppm) of yeast are only 10% more dense than the wort/beer then
> the excess of about 500ppm gives a 0.5SG degree error !
>
>
That's about what I observed. I'm saying that's not significant for most
purposes.
>> I opined the other day that one ought to be able to easily acheive
>> 0.2P accuracy
>
>
> 0.2P ~= 0.8SG degree just under 1SG degree -I agree that's about the
> level
> where the going gets tough.
>
I guess my whole point is that a couple of tenths Plato is plenty good
for the purpose as hand. I propose ADF (1 - ratio of present to
original gravity) expressed as a percentage as the metric of
fermentation progress. If the two Plato readings are in error by 0.2 and
the OG is 12 then the standard deviation in the ADF is around 2%. Do I
really care if my observed ADF is 70 or 72%. No, I don't (though others
may and they can use pycnometers if they choose).
>
> Right - but this means calibrating the hydrometer, controlling
> temperature
> and degassing .... then of course reading correctly through the meniscus.
>
Well no, I purposely did not do the cleaning protocol nor calibrate the
hydrometers nor attemperate nor remove the yeast nor apparently even
read through the mensiscus correctly. I wasn't trying to see if I could
get "slightly less precise" than an electronic density meter. I was
trying to see if I would read within 0.2P of an electronic density
meter. I believe that if I did all those things I could get "slightly
less precision but IMO a large part of the value of a hydrometer reading
is that it is simple and quick. If I thought I needed 5 decimal places
I'd use the density meter. Anyone who thinks I'm crazy not to has
clearly never cleaned one.
>> I took a sample into a hydrometer jar [...] I put enough sample in
>> the jar that the fluid displaced overflows the top (as the ASBC likes)
>
>
> Funny but my hydrometer mfgr suggest sighting from below then bringing up
> your field of vision the lower side of the liquid surface. They claim
> their procedure is adapted from a NIST circular.
>
One should follow the manufacturers directions. When dealing with beer
we bow to ASBC and probably should be using ASBC hydrometers (which are
available but I don't know from whom - contact the society).
>
> Hold that thought AJ - what if the average HBer doesn't have a density
> meter to calibrate against and is off by 0.2P or 0.3P ? Also they are
> using a little $6 hydrometer where the meniscus 'blind spot' spans 2SG
> degrees - 0.5P. My NIST referenced ERTCO has systematic error around 0.4P
> so it's not unlikely. I certainly think 0.2P is do-able, but I don't
> think
> it's quite so easy.
>
My admittedly anecdotal experiment shows that you don't need an
electronic density meter to calibrate against if you have decent
hydrometers and use them properly. That is for the 0.1 - 0.2P level of
accuracy - you won't get to the "sligtly less precise" level without
calibration against pycnometer or electronic meter. The problem is that
without the more elaborate equipment you can never have full confidence
in your readings beyond that which comes from knowing you've bought
decent gear. A good set of brewing hydrometers won't break you but they
will cost you more than $6.
>
> You seem to have both high resolution and very accurate hydrometers AJ
> (is it 8P range, 0.2P resolution & accuracy ? Or have you calibrated
> these
> ?)-would you care to mention the type/vendor ?
>
I can't. The entire printed matter on them says "Balling saccharometer,
60F, Made in USA". There are three of them: 0-8.5P, 7.5 - 16.5 P and I
don't even know where the third one is at this point. As I mentioned
the scale is about 1 cm per degree and the stems are skinny (about 4 mm
dia.). I got them years ago from a mail order shop in Carolina
somewhere. I've noticed that Beer, Beer, and ... has a set and as I said
I believe ASBC has approved a set.
Cheers, A.J.
------------------------------
Date: Sat, 03 Dec 2005 12:12:09 -0600
From: Michael Owings <mikey at swampgas.com>
Subject: Refractometer use during and post-fermentation
Louis Bonham posted a formula sometime ago (search the HBD archives) that
can be used to correct a refractometer reading taken during fermentation
for alcohol produced, provided the starting gravity is known. I wrote a
small program to implement this, and ProMash includes a calculator that
handles this type of correction as well.
You do need to do a little calibration, as the formula will not be accurate
for all instruments. In my case, the reading is a consistent 2 or 3 SG
points (.50-.75P) points low, as compared against a narrow-range lab
hydrometer. The type and gravity of beer produced doesn't seem to affect
the error at all. In general, I add 3 points to any reading taken during
fementation.
Note that if you intend to use the refractometer during fermentation, the
suspended yeast will blur the line a great deal. You can mitigate (but not
eliminate) the blurring by filtering the sample through a couple of paper
towels or filter paper (coffee filters might work -- I just use a couple of
paper towels).
Otherwise, my $89 refractometer agrees with my narrow-range hydrometers to
around 1 SG point on unfermented wort -- regardless of composition. This
should be good enough for most homebrewers.
Hope that helps -- m
- --
Teleoperate a roving mobile robot from the web:
http://www.swampgas.com/robotics/rover.html
------------------------------
Date: Sat, 3 Dec 2005 14:41:33 -0500
From: "Jay Spies" <jayspies at citywidehomeloans.com>
Subject: Eating Hops
All -
This post just reminded me of my friend Sam, who I brew with, who is such a
hophead that during a brew session he'll take a whole hop or two and plug it
between his cheek and gum like tobacco... When I ask him how that tastes,
he simply responds with a loud whooping "HOPS, buddy!!" as a response.
Funny guy, a little off center, but funny.
You know what they say, you can take the boy out 'da country, but.....
Jay Spies
Head Mashtun Scraper
Asinine Aleworks
York, PA
------------------------------
Date: Sun, 04 Dec 2005 07:03:14 -0500
From: "steve.alexander" <-s at adelphia.net>
Subject: hydrometer - Howto calibrate ? measurement temp!
A.J deLange wrote:
> steve.alexander wrote:
>> I've got a pair of Ertco's and the first (1.000 -1.070, resolution
>> 0.0005, and same for accuracy (hah!)) has a calibration error very
>> close to 1.75SG degrees !
>
> If you know you have a systematic error take it out!
I do of course (they'd be useless without), but my point is that the
systematic error may be very high, and I don't recall ever seeing
hydrometers packaged with a calibration procedure. I seriously doubt
the average HBers calibrates, knows how to calibrate nor has the
tools handy to calibrate a hydrometer to any decent accuracy.
I hope AJ, who is much closer to he physical chem & instrumentation
issues than I am, will suggest a hydrometer calibration procedure that
an HBer, without access to "Lab deLange" can use to "easily achieve
0.2P accuracy". Yes, this is a challenge to AJ's thesis that 0.2P
readings are trivial, but meant to be a constructive and positive one.
Well degassed distilled water at spec temp is the obvious starting point,
but then to create a 'known standard' higher gravity fluid for the other
typically requires a relatively cheap volumetric measure and a considerably
more expensive mass measurement. I haven't carried through the error
terms with any care, but I expect that to make a stock 1L of 8P solution
accurate to some small fraction of 0.2P requires a scale capable of
measuring just over 80 grams to considerably better than 0.2 grams.
Some ~$100 scales will match that resolution, but accuracy statements
are hard to come by at that price. The liter volumetric needs to be
accurate to w/in a small fraction of 25ml for comparable accuracy.
Then there is temperature. This isn't exotic lab gear by any means, but
it's also not "kitchen gear".
Maybe there is a more accessible approach to calibration that I am
missing - using only thermal expansion of distilled water, or perhaps
a method relying on the limiting solubility of some solute ...
My *hunch* (and I'd love to be proven wrong) is that calibrating your
shiny new $20 hi-resolution hydrometer the first time to well under
0.2P will require a several hundred dollars of equipment and an
afternoon. Without the calibration you may as well see if a witch
will float in your wort - hydromancy.
>> Lessee, 0.080 SG degrees is less than atmospheric pressure
>> variations will cause on a hydrometer -
>
> Don't think I agree with that.
I need to review this (later). It may have been the GL-XMas Ale
mis-calculating that one but your outline analysis 'feels' wrong.
> As I recall the whole point of the Normal-Eichungskomission was to
> deal with known errors in the Balling tables. These were mostly in
> the 5th and 6th decimal places.
One table (not the one I was initially thinking of) appears in v1 of
M&BS appendix as table A.5. Ignoring the Balling & Baume columns it
claims is based on Dr.Plato's Normaleichungskomission work. I will
openly admit that I have never been happy with this table - something
about the explanation confuses to me. Still it *appears* to show, for
example an SG difference at 60F vs 20C of (1.0550 - 1.05476) several
tenths of an SG degree (4th decimal place) at reasonable brewing gravity.
It's too small to be temp correction. and oddly the Balling SG at 17.5C
for this row does not fall between the 60F(15.6C) and 20C figures.
Maybe I am misinterpreting whatever this table is trying to convey.
Let's not get caught up in the tables and miss the point; as brewers we
are measuring SG commonly from 1.005 - 1.060 in solutions that consist
of mostly (~85+%) water with the remainder being a complex mixture of
sugars, dextrins ethanol and a large number of lesser ingredients. If
you use your hydrometer away from it's reference temp and then
use a WATER expansion coefficient to "correct" the SG reading, then
you have committed a sin. The other 15% of "stuff" is quite unlikely
to contract and expand with temp in precisely the way water does.
It seems clear that this could create an impact in the tenths of an
SG degree range over 5C. Water density from 15C to 20C
changes from 0.999103 to 0.998207, so a temp correction table might
suggest you subtract 0.000896 when measuring at 20C using a 15C
referenced hydrometer. For pure ethanol the density is 0.79367 to
0.78945 at 15&20C so the SG correction needed for pure ethanol would
be 0.004220 - or almost 5 times as much. Now *IF* ethanol in a
water solution behaved the same, and if we made up a 7% ethanol
solution and measured it at 20C with our 15C hydrometer and
corrected using the water expansion correction - the error would
be about 0.000232. or about 1/4 SG degree across 5C in a 7% EtOH
solution. Then we have maltose, glucose and all the rest to consider.
A hydrometer with any scale comes to rest when the hydro mass divided
by the submerged volume equals the liquid *density*. This is true
regardless of temperature.
The "SG" scale merely relates this density reading to the density
of water at some spec temp and then gets all tangled up with the
issue of changes in Dw wrt temp since *usually* the liquid is
mostly water and this is then a decent first order correction.
The Plato scale relates the density to that of a sucrose solution
{with a certain percentage of sucrose extract per unit mass} with
identical density. This is a better model for wort than is water,
but there is no temperature characterization, and why read finished
beer density in terms of Plato? That's hilariously indirect. 2P
beer doesn't contain 2% of anything - it's merely a reference to
a similarly dense 20C sucrose solution.
Beer/wort is what we are measuring and this is neither water nor
sucrose solution. With a hydrometer of either sort, one can
accurately calculate the density of the beer/wort at the *measured*
temperature, but no other. Temp correction tables often supplied
in HB books or even from hydro manufacturers imply this can
be done, but it's really a crude estimate.
If we measure wort at 17C, then estimate its SG at 20C
by assuming it acts like water, and then estimate the extract%
assuming it acts like sucrose solution ... that's fine - but it's
several leaps of faith away from any literal observation.
-S
------------------------------
Date: Sun, 4 Dec 2005 22:08:12 -0500
From: "Pat Babcock" <pbabcock at hbd.org>
Subject: Northern Brewer Sponsors HBD For 2006!
Greetings, Beerlings! Take me to your lager...
I quick note to point out that the header of the Digest will
not be changing for 2006. Once again, Chris Farley and the
folks at Northern Brewer have come through to sponsor the
HBD again for 2006.
Being employed by an automaker, these times are particularly
scary - though I like to think that I'm indispensible to the
company, people have been losing their jobs all around me,
and I can't say with any certainty that I won't be next.
Sponsors like Northern Brewer help to ensure that the HBD
can continue if such a tragedy were to occur. And their
early renewal helps take the burden of supporting the HBD
off my mind for the year. My genuine thanks and
appreciation goes to them. So should yours - support those
who support you!
Thanks, Chris! And thanks again, Northern Brewer!
- --
See ya!
Pat Babcock in SE Michigan
Chief of HBD Janitorial Services
http://hbd.org
pbabcock at hbd.org
------------------------------
End of HOMEBREW Digest #4903, 12/04/05
*************************************
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