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	FORUM ON BEER, HOMEBREWING, AND RELATED ISSUES
		Digest Janitor: janitor@hbd.org


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Contents:
  potassium meta bisulfites (larry.suarez)
  RE: Dr. Cone Q&A (eIS) - Eastman" <stjones at eastman.com>
  Bottle conditioning lagers ("Fred Scheer")
  yeast pitching/ MHing (Marc Sedam)
  Electrical Element Wattage Density ("Dan Listermann")
  re: you've got mail (Rama Roberts)
  CO2 Safety (again) (Calvin Perilloux)
  Oxygen ("Ronald La Borde")
  O! O, nO! It's nOt O2! (Pat Babcock)
  CO2 effects ("Pete Calinski")
  Oxygen Toxicity ("John Adsit")
  Bubbles, Tiny (and big) Bubbles ("Dave Burley")
  Toronto Tips (Bob Hall)
  240V vs 120V... ("Mike Sharp")
  Dr.Cone Responds-Follow Up Questions- Steve Alexander ("Rob Moline")
  Dr. Cone Responds-Top 5-David Sweeney ("Rob Moline")


* * * * * * * * * * * * * * * * * * * * * * * * * * * * *
*           The HBD Logo Store is now open!             *
*            http://www.hbd.org/store.html              *
* * * * * * * * * * * * * * * * * * * * * * * * * * * * *
*   Beer is our obsession and we're late for therapy!   *
* * * * * * * * * * * * * * * * * * * * * * * * * * * * *
* * * * * * * *       IN  PROGRESS!       * * * * * * * *
*          Dr. Clayton Cone Fortnight of Yeast          *
*      8/11/03 - 8/22/03 Yeast Questions Answered       *
* * * * * * * * * * * * * * * * * * * * * * * * * * * * *

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----------------------------------------------------------------------


Date: Mon, 25 Aug 2003 07:52:53 -0400
From: larry.suarez at gm.com
Subject: potassium meta bisulfites

Does anybody know how to adjust the sulfites levels in wine just before
bottling?




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Date: Mon, 25 Aug 2003 08:39:26 -0400
From: "Jones, Steve (eIS) - Eastman" <stjones at eastman.com>
Subject: RE: Dr. Cone Q&A

David Houseman makes a good suggestion to create an archive of the Dr.
Cone Q&As from this year's session.

I will be compiling all the Q&As from this session for my own use
anyway, and have a club web site available (on the HBD server), so I'd
be happy to make them available to anyone for downloading.

Steve Jones, Johnson City, TN
State of Franklin Homebrewers (http://hbd.org/franklin)
[421.8 mi, 168.5 deg] AR




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Date: Mon, 25 Aug 2003 08:40:24 -0400
From: "Fred Scheer" <fhopheads at msn.com>
Subject: Bottle conditioning lagers

After my HB lagers endfermented, and lagered for ~ 4 weeks, I start a new
HB lager. At the same day, I take the amount I want to bottle conditioning
out of lagering and let the temperature raise to ~ 50*F.
After the second brew reaches high krausen (usual the 3th day), I take
~ 1 liter of that wort and ad to the 5 gal I want to bottle.
I had no problems in the past with that procedure.
Thanks,
Fred Scheer



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Date: Mon, 25 Aug 2003 08:55:45 -0400
From: Marc Sedam <marc_sedam at unc.edu>
Subject: yeast pitching/ MHing

On mash hopping...

Thanks to Fred Scheer for his data point on mash hopping.  Fortunately, 
since I'm trying to build some kind of model to show why it might work, 
Fred's observation fits...maybe.  Fred, do you have any recollection of 
the water chemistry?  I use mash hops not for bittering, but for flavor 
and aroma.  My all mash-hopped pilsner is a big favorite of my friends, 
mostly for the hop flavor.

One other interesting data point from the mash hop archives.  I recently 
took a vacation to Pacific City, OR and stopped by the Pelican Pub and 
Brewery.  If your idea of a good time is staying in a nice inn with a 
great view of the ocean and a small brewpub across the street, I highly 
recommend the visit.  Pelican Pub makes absolutely wonderful beers and I 
was lucky enough to have a tour of the brewery with the brewer, Darron 
Welch.  

Darron has mash hopped his winter warmer for the past few years (I 
acquired two bottles..lovely) and noticed that the runoff was crystal 
clear.  I have noticed the same thing on a small scale and thought this 
too might be pH related...but Darron gave me a better 
explanation--surface area.  He proposed that the increased surface area 
in the hopped mash gave more places for proteins and particulates to 
settle.  It mirrors my observations and Darron mentioned that other 
breweries using mash hopping see the same thing.  So there ya go!

Regarding yeast pitching...

The conventional wisdom is to not repitch after your high-gravity 
fermentation.  I would say that a 1.060 IPA doesn't quite qualify as 
high-gravity, although others may differ.  What I have done in the past 
when dealing with this issue is to pitch a couple of quarts of starter 
wort on the big yeast cake the day before.  It gets the yeast chugging 
again, and the resultant high-gravity fermentation seems fine.  However, 
I would bet you could pitch the same yeast through those three batches 
without ill effect.

Cheers!
Marc

- -- 

Marc Sedam
Chapel Hill, NC




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Date: Mon, 25 Aug 2003 09:17:23 -0400
From: "Dan Listermann" <dan at listermann.com>
Subject: Electrical Element Wattage Density

 Dion Hollenbeck <hollen at woodsprite.com> posts on this subject.  For years I
have used common hot water elements to boil my brews.  I run them at 240V.
I have used a 5500W element and, if memory serves, it produced over 100
watts per square inch.  I never noticed scorching,  although there was beer
stone build up that had to periodically be removed.  I eventually changed to
4500 watts because the bigger one would boil over easily.  I am designing a
bigger system and will probably go back to 5500W.  I don't foresee any
problems if experience is any guide.

Dan Listermann

Check out our E-tail site at www.listermann.com

Free shipping for orders greater than $35
and East of the Mighty Miss.






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Date: Mon, 25 Aug 2003 08:20:57 -0700 (PDT)
From: Rama Roberts <rama at sun.com>
Subject: re: you've got mail

> I got about 5 from the HBD mail responder. As if the spam problem wasn't
> enough, this starts to make email unusable as a communication media.
>  All the best and a spamfree homebrew   Thomas

Its been getting bad for me too- I've affectively modified my spam filter
to catch the incoming sobig.f, but as janitor Pat mentioned earlier, its
the bounces or autoresponders complaining about the emails with your
address as the faked From address that really suck. They all look
different, so its hard to positively identify and filter them.

On a good note, Pat and I have been discussing a fix that will help limit
future spam. The HBD archives expose email addresses as Mailto links-
perfect for "scrapers" to harvest them and pass them on to spammers. Our
plan is to convert those addresses, for example:
	billgates at microsoft.com
to
	billgates AT microsoft DOT com

or some such to prevent automatic scraping.
Hopefully Pat and I will implement this quick fix in the near future.

- --rama



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Date: Mon, 25 Aug 2003 09:20:27 -0700 (PDT)
From: Calvin Perilloux <calvinperilloux at yahoo.com>
Subject: CO2 Safety (again)

"Tanksalot" in the previous HBD:

>> To test my theory I "poured" a glass of CO2 gas and 
>> inhaled it, obviously I'm still here.  The only sensation 
>> was the same you get from smelling the gas released by soda 
>> water.  I'm not a chemist, so maybe someone more familiar 
>> with gases (is that a word?) can jump in...

You didn't get a high enough concentration of CO2.  Really.
By "pouring" it, even though CO2 is about 1.5 times the
density of air, you're mixing it and reducing concentration,
probably below 20%, considering the effect you're talking about.
Try instead purging a container (of liquid) with CO2 so that
you get pure CO2 in there, and you'll get a nice nip in the
nose, or more.  I guarantee.  Don't do this with a container
you might fall into!  Let me assure you that Drew and Ed 
didn't have something else in their fermenters causing that.

John Koppens asks whether CO2's hazards come from air displacement
or toxicity.  I think it's a mix, and anyone considering this
issue can do some thorough Google checks and get lots of data
to add more detail to this:  

CO2 does have major effects even in concentrations where it's 
obviously not displacing enough O2 to cause such intense problems.
This could be because the concentration in the air is inhibiting 
the respiration of it from your lungs, possibly even dissolving
into the blood instead of out of the blood.  And the formation 
of carbonic acid on the tender tissues in your nose/eyes/lungs 
is also something that you won't find with an inert asphyxiant 
like nitrogen or argon. 

More safety data, and then I'll stop, lest this thread never die,
from the Canadian version of OSHA, some info on CO2 toxicity: 

http://www.ccohs.ca/oshanswers/chemicals/chem_profiles/
carbon_dioxide/health_cd.html

"Exposure to 10% for 1.5 minutes has caused eye flickering, 
excitation and increased muscle activity and twitching. 
Concentrations greater than 10% have caused difficulty in 
breathing, impaired hearing, nausea, vomiting, a strangling 
sensation, sweating, stupor within several minutes and loss 
of consciousness within 15 minutes. Exposure to 30% has quickly
resulted in unconsciousness and convulsions.  Several deaths 
have been attributed to exposure to concentrations greater 
than 20%. Effects of CO2 can become more pronounced upon 
physical exertion, such as heavy work." 

Calvin Perilloux
Middletown, Maryland, USA




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Date: Mon, 25 Aug 2003 12:21:24 -0500
From: "Ronald La Borde" <pivoron at cox.net>
Subject: Oxygen

I am as guilty as everyone else who keeps listing O2 for oxygen.
Apparently the atomic symbol is O, not O2.

I was looking around and came up with this reference:
http://pearl1.lanl.gov/periodic/elements/8.html

Ron
=====
Ronald J. La Borde -- Metairie, LA
New Orleans is the suburb of Metairie, LA
www.hbd.org/rlaborde





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Date: Mon, 25 Aug 2003 14:03:14 -0400 (EDT)
From: Pat Babcock <pbabcock at hbd.org>
Subject: O! O, nO! It's nOt O2!


Greetings, Beerlings! Take me to your lager...

pivoron at cox.net writes:

> I am as guilty as everyone else who keeps listing O2 for
> oxygen. Apparently the atomic symbol is O, not O2.

Oh, Gads! Who picked THAT nit?

Yes, yes, yes: the chemical symbol for Oxygen is O. However,
nature doesn't care what symbol we chose for it. She refuses to
allow Oxygen to travel alone. When you breathe it, it's coming
with another buddy; hence, in nature, it's O2. Molecular oxygen;
not atomic oxygen. Yeah, it's briefly O in the formation of
ozone (O3); however, O is not stable, and we do not add O to our
wort. We add O2. So stop picking nits already: when we're
talking about oxygenation, it is quite proper to refer to it as
O2.

Nyah.

Did you know that they've proven O4 exists?
(http://www.nature.com/nsu/011122/011122-3.html).

Back into the padded cell...

- -- 
 -
God bless America!

Pat Babcock in SE Michigan         pbabcock at hbd.org
Home Brew Digest Janitor           janitor@hbd.org
HBD Web Site                       http://hbd.org
The Home Brew Page                 http://hbd.org/pbabcock
[18, 92.1] Rennerian
"I don't want a pickle. I just wanna ride on my motorsickle"
                                   - Arlo Guthrie





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Date: Mon, 25 Aug 2003 12:13:54 -0400
From: "Pete Calinski" <pjcalinski at adelphia.net>
Subject: CO2 effects

This may be an old wife's tale but I was told that when the concentration of
CO2 in the lungs gets high enough, it forms carbonic acid and that causes
the burning sensation.

OTH, nitrogen does not have this effect so there is no warning that you are
not getting enough oxygen.  You just pass out.  Thus, you will see nitrogen
sensors in areas where nitrogen is stored.

Pete Calinski
East Amherst NY
Near Buffalo NY

http://hbd.org/pcalinsk


***********************************************************
*My goal:
*      Go through life and never drink the same beer twice.
*     (As long as it doesn't mean I have to skip a beer.)
***********************************************************



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Date: Mon, 25 Aug 2003 13:13:07 -0600
From: "John Adsit" <j.adsit at comcast.net>
Subject: Oxygen Toxicity


> From: "Tanksalot" <tanksalot at rogers.com>

> Kevin said, "actually even breathing O2 can kill you".  (I assume, Kev,
> that is a typo, as O2 is oxygen).

I believe the point was that anything is toxic under the right conditions,
and that is indeed true for oxygen.

Central Nervous System Oxygen Toxicity can occur when breathing too much O2
under more than one atmosphere of pressure.  It causes immediate seizures.
Scuba divers who use enriched air (Nitrox) need to know the depth limit for
the particular blend they are using, and they should track the O2 buildup
over repeated dives.  Seizures from CNS toxicity are usually fatal, since
the diver will probably drown.

Pulmonary oxygen toxicity causes damage to the alveoli in the lungs, and it
is associated with breathing high concentrations of O2 at normal pressure
over a prolonged period of time (like days).

Of course, this is not something that brewers need to worry about, unless
they take up diving as well.  But the actual point is valid: enough of
anything under the right conditions can kill you.

John Adsit
Boulder, CO
j.adsit at comcast.net
 .




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Date: Mon, 25 Aug 2003 18:51:16 -0400
From: "Dave Burley" <Dave_Burley at charter.net>
Subject: Bubbles, Tiny (and big) Bubbles

Brewsters,

/Fredrik is counting CO2 bubbles in the airlock. I did this at the beginning
of my brewing career also, so I understand.

One thing you must remember is that CO2 is soluble in water/beer and this will
skew your results, as the fermentation can proceed for a while before any
bubbles come out.  Temperature is a problem to be accounted for, as solubility
of CO2 is temperature dependent.

But the largest variable and least accountable for variable is the fact the
CO2 in a water system is slow to come to equilibrium ( and thank goodness!)
were it not, we would get a shower of beer every time we opened a bottle.

You could try agitation during fermentation or other mechanical means to bring
the CO2 to equilibrium, but this has apparently ( IOW , jury is still out in
my book)  been shown to have adverse effects on beer quality.

Point is, bubble counting is not a good measure of fermentation rate until the
fermeting fluid is saturated and not even then due to the non-equilibrium
release of CO2.

Keep on Brewin'

Dave Burley




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Date: Mon, 25 Aug 2003 19:00:02 -0400
From: Bob Hall <rallenhall at toast.net>
Subject: Toronto Tips

My wife and I will be in Toronto for a few days in September and will be 
staying at the Delta Chelsea, 33 Gerrard Street West. We won't have a car, 
so any tips about brewpubs, beer bars, or beer supply stores in that part 
of town would be appreciated. Many thanks.

Bob Hall,
Napoleon, OH



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Date: Mon, 25 Aug 2003 18:06:51 -0700
From: "Mike Sharp" <rdcpro at hotmail.com>
Subject: 240V vs 120V...

I had to chime in on Dion's cautionary post...

>>Gary Smith writes:

GS> I would like to find a leg from the other side of the breaker box,
GS> add another Solid State Relay and connect it as 220V just to
GS> accelerate the ramping times during mashing somewhat.

And Dion emphatically states:

"DO NOT, I repeat, DO NOT do this."

And also states:

"Caramelization and localized denaturing of enzymes
are sure to happen if you run the heater element at its full heat
capacity on 240V."

I have to respectfully disagree.  Nobody said anything about
running the heater element at full capacity...he simply said he
wanted to run it at 240V.  He's using a PID controller, not
connecting it across the line.  Line voltage and power are not
related here, because the power is controlled by time domain
proportioning.  Depending on the tuning of the controller, he can
run the heater at any wattage from zero to 6000W. It entirely
depends on the proportion of the "on" time to the "off" time.
This can be set in the controller.

Let's say he wants to slightly increase the ramp rate.  What he
really wants is, say, 1800 watts instead of 1400 watts.  Assuming
he has a cycle time of about 1/2 second, at 240 volts
he'll have to set the maximum percent so that the max "on" time is
about 23% to produce 1400 watts of heat, or 30% to produce
1800 watts.

On an Omege controller (well, on the CN7700 series), you do this by
specifying the the value in the Maximum/Percent High submenu.

The actual maximum watt density he can use without carmelization
is going to be dependant on several factors, one of which is flow
rate.  But in his case, I see nothing wrong with using 240volt on the
heater, when a PID controller is involved.  Obviously there is a maximum
desireable watt density, and he'll have to determine his maximum
ramping rate some way.

Personally, I prefer instrumented heating elements.  These have a
thermocouple installed inside the rod, bonded to the surface. These
are nice because you know exactly what the rod surface temp is.  But
Gary's heater rod can easily be run at 240v, using PID control.

Regards,
Mike Sharp



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Date: Mon, 25 Aug 2003 21:43:00 -0500
From: "Rob Moline" <jethrogump at mchsi.com>
Subject: Dr.Cone Responds-Follow Up Questions- Steve Alexander

		Dr.Cone Responds-Follow Up Questions- Steve Alexander

   Great thanks for considering my questions Dr.Cone.
   Many HBDers like to store yeast slurries.  Storage under finished beer or
deionized water at refrigeration temperatures is common.   Some homebrewers
reuse these stored slurries after as much as 60 days of refrigeration !   I
have very grave concerns about the vitality and viability after such long
storage and think that 30 days storage is pushing the envelope.
   1 - What is an acceptable  figure for pitched yeast viability (say by a
haemocytometer + MethylViolet stain count).   Is the commercial target of
90% viability too stringent  for the homebrewing  environment ?
   2 - What is the viability of properly rehydrated dried yeast like
Lallemand's ?
   3 - Please comment on  the expected vitality and viability of a wet
homebrew
slurry stored at refrigeration temperatures for various periods.  Obvious
there is no definite answer to such a general question, but perhaps you can
suggest how long is 'probably OK' ?  How long is 'likely too long' ?
   4 - Some yeast vendors package wet yeast in refrigerated 'pitchable'
tubes. Is there any means that they could employ to improve the yeast
storage
properties beyond that of a homebrewer's refrigerated slurry?  For example,
does anaerobic handling or phosphate buffers, etc improve 'fridge shelf life
of a wet slurry by a great amount ?.
   5 - Does the iodine test (iodine into slurry sample to detect glycogen)
have any comparative value to homebrewers as a quick and dirty test of
slurry
vitality ?   [Some sources state brief exposure to O2 will  rapidly deplete
yeast glycogen .]
   6 - What are the consequences of pitching low viability slurries given
that sufficient viable cells are pitched ?  If I pitched one unit of 100%
viable
slurry versus 3 units of 33% viable slurry what would be the expected
difference in the beer ?   Autolyse of non-viable cells ?  Other ?   Does
racking the beer off trub to a secondary prevent this harm ?

On a different topic ...
   Many HBers build up large yeast starters, but they do not wish to dilute
their 5 gallon batch of XYZ-style wort with several quarts of pedestrian
starter wort.    They wish to separate the yeast from the starter wort
before pitching.  Many will allow the starter fermentation to nearly
complete then refrigerate it and allow the yeast to sediment before
decanting and pitching .
   7 - Does the <attenuation, refrigeration, sedimentation, separation>
process hold potential harm for the yeast ?  For example is the yeast likely
to be
less vital than if pitched directly from a high kreusen starter ?

Yet another direction ...
   8 - Is there any significant advantage to *very* short 'lag times' (time
between pitching to first sign of  fermentation - usually CO2 outgassing) ?
Many HBers seem obsessed in reducing lag times from 8 hours to 5.
Personally I doubt it makes much difference so long as the lag period is
reasonably brief.
   I know that 8 koans in Cone's fountain is a bit, but hopefully some admit
concise answers.
thanks again,
 -Steve Alexander


Steve Alexander,
   Good straight forward questions.  I wish that I had good, simple, short
answers. You have a right to be concerned about the quality of the yeast
stored under refrigeration for as much as 60 days. Some people may tell you
that they do it all the time and still have successful fermentations with
it.  The gods must be looking after them.

   My answers below are shared comments by my collegue Dr. Tobias Fischborn.

   Ad 1) the viability for liquid culture (crop yeast) is also an
indication for the physiological state or vitality of the yeast.
If the viability is relatively low then there was something wrong (stress,
nutrient deficiency...) during the previous fermentation and the "viable
yeast"
is probably not in very good condition as well. Therefore a viability of
more than 90 % would be good standard to maintain.
   Ad 2) For dry yeast it is a bit different. Here some yeast will die
during the drying process and even more during the rehydration process.
But this is an unavoidable process related loss and does not say
anything about the physiological state of the viable cells. You will
always have higher numbers of dead cells in dry yeast. The vitality of each
live cell will be great.
Usually the viability will be greater than 85%. The viability will be above
90% after a few multiplication cycles.
   Ad 3) It depends on how you store your yeast. There are reports that you
can store yeast up to 1 year in distilled water if all sugars are
removed. We have a little program running to test this and after one
month the yeast is still fermenting well. But it is critical that all
sugars are removed. A lot of breweries keep their yeast for up to a
month under water (removing the wort/sugar residuals) without any
problems.
   Ad 4) to my knowledge they are no special tricks to improve shelf life
of commercial liquid cultures. These commercial cultures are propagated
in nutrient rich media under optimum conditions means the yeast is very
healthy when harvested and can be stored longer than crop yeast from a
fermentation.
   Ad 5) For the iodine test you need a microscope. Other wise you don't
know if the starch/glycogen you are detecting is inside living yeast or
if it is in the medium coming from starch residuals in the wort or
released from dead yeast. Oxygen will deplete glycogen in yeast.
   Ad 6) see ad 1. 100 % viable pitching yeast is very vital (healthy)
compared to the 30 % viable yeast. So even if you compensate with a
higher pitching rate you will have problems in the fermentation.
Autolyses of non-viable cells is definitely an issue.
   Ad 8) You are probably right!! I don't believe there is a significant
advantage in-between 5 hours and 8 hours lag time. It is when the lag
phase begins to extend well beyond this time period that you would begin
to suspect a weakening of the pitching yeast. The HBers that try to keep the
lag phase below 8 hours and moving down toward 5 hours are to be
complimented on their efforts. It means they are doing all they can to keep
a healthy yeast
for pitching.

Clayton Cone

- ---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.512 / Virus Database: 309 - Release Date: 8/19/2003



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Date: Mon, 25 Aug 2003 21:52:15 -0500
From: "Rob Moline" <jethrogump at mchsi.com>
Subject: Dr. Cone Responds-Top 5-David Sweeney

			Dr. Cone Responds-Top 5-David Sweeney

Dr. Cone:
   My brain is about to explode with all of the biochemistry (they don't
call it BICH for nothing!). I took it in college but try not to think about
those horrible days.
   In Fix's book _Principles of Brewing Science_, George outlines a list
of the most critical controllable elements of the brewing/fermenting
process for homebrewers, for example, fermentation temperature,
pitching volume, etc.
   Since I is a Aggie, I have trouble with lists larger than I can count
on one hand.  So my question is this: What are the top five
controllable variables (in order of importance) with regard to yeast
for the homebrewer?
David Sweeney
Texas Aggie Brew Club (TABC)


David,
   I agree.  My mind gets migraines too from trying to remember all the
biochemistry, metabolic pathways and genetics.  Thank goodness, some smart
fellows have figured it all out for us.  It has erased a lot of the
mysteries and explains why all the controls are necessary and what goes
wrong if you don't have controls.  Dr. Fix was great at explaining in layman
terms. I wish that I had his talent.
   I have spent over 55 years working with yeast: R&D, Q.C., production and
its
industrial application---baking, pharmaceutical, brewing, distilling and
winemaking. The one common denominator for a successful fermentation in each
field has been  "healthy yeast cell". Concentrate on starting with a healthy
yeast and ending with a healthy yeast. If you Re-pitch, store as cold as
possible (4C) and start with a new culture as often as possible. After 5
cycles you are taking a chance with infection build up.  After 10 - 15
cycles you are taking a chance with petite mutates, genetic drift, cell wall
hydrophobicity change and flocculation characteristics. If you are not
critical about fermentation time and the flavor profile you may get away
with more re-pitching cycles.  If you are critical about fermentation time
and flavor profile then you will hold re-pitching to a minimum.
   Temperature control is right at the top of the list of variables to
control,
starting with the mashing temperature. If you skip the protein enzyme phase
around 45C you will end up with a wort that is low in amino acid  nutrients
for the yeast. 68C mashing will give you an entirely different sugar profile
with less fermentable (more unfermentable) sugars than 60C mashing. Several
cycles with low nitrogen will begin to produce a weak yeast. An increase in
unfermentable sugars will lead to higher attenuation gravity and you will be
wondering why the fermentation does not attenuate.
   Good beer can be made from extracts, however, you must remember that some
to
all amino acids are tied up by the Maillard reaction during the preparation
and storage of the extract. Consider adding a well balanced yeast nutrient
like Fermaid K to an all malt extract fermentation especially if you are
going to Re-pitch.  This will go a long ways towards maintaining a healthy
yeast cell.  A product like Servomyces will give you yeast an added boost.
   Higher gravity wort with increased levels of sugar require more well
balanced nutrients supplementation, especially as you begin to re-pitch.
   Follow the yeast supplier's instructions very carefully for start up..
The
Active Dry Beer Yeast rehydration instructions are extremely important.
Success and failure begins at this point.
   With a healthy yeast, pitching rates are easier to estimate.  You do not
have to guess at how much over pitching that you need to make up for poor
yeast health, viability and vitality.
   You asked for the five most important variables to control in order of
importance and I have talked around your request by emphasized the health of
the yeast cell. With a healthy yeast, controlling the variables becomes
meaningful.
   If I have to list five variable that should be given careful attention:

Wort preparation and composition
Yeast strain
Pitching rate (and storage)
Fermentation temperature
Well balanced nutrients
Oxygen (this can be considered a nutrient also)

   My answer may not be as precise as you would like.  Perhaps it will open
a
dialogue.
Clayton Cone
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