Correction: Oxygenation

In my writeup of oxygenation, I screwed up some of my basic chemistry.  A mole of O2 masses 32 grams, not 16 as I used.  That will halve the times listed:  To get one ppm of oxygen in 20 liters (five gallons plus about a quart) at a flow rate of 1/32 liters per minute, you’ll need half of 1.2 minutes, or about 0.6 minutes of oxygen flow.  Round up to account for inefficiency and you can just about say 1 minute per ppm desired.  For 8 ppm, use about 8 minutes.

It’s been 40 years since high school chemistry.  I apologize for the error.

Oxygenation vs. Aeration

Got this guy over the summer:


That’s a William’s Brewing Big Oxygen system hooked up to a 20 CF oxygen tank.  So the question becomes how much oxygen to use.  Warning:  Chemistry and algebra follow!

The desired oxygen level is about 8 ppm.  You can almost reach this by using air, either through extended shaking or using a aquarium pump and an airstone, although it’s not sufficient oxygenation for a larger beer.  And it’s inexact.  If you’re shaking or using air and your lag times are variable, look to dissolved oxygen as the cause:  The oxygen running out is the yeast’s signal to switch over to anaerobic fermentation, the one that makes beer.

References call for oxygenating for a minute at a flow rate of 1 lpm.  This makes some awfully big bubbles in the wort.  The bubbles aren’t the problem, their surface area is.  Bigger bubbles mean less gas in contact with the wort and the gas can only dissolve if it’s in contact so smaller bubbles are better.  So I set out to find out how much oxygen for how long I’d need to get first 8 ppm of oxygen in solution, then for later ease of calculation 1 ppm.  I’ll work through the 1 ppm example.

The regulator is adjustable for different flow rates.  Lower flow rates mean smaller bubbles.  Ideally, the wort should dissolve everything and the bubbles should not reach the surface.  Since 1/32 LPM (liters per minute) is the lowest flow rate, I decided to base my calculations on it.  So to start, how many of you remember the ideal gas law?  Thought so, it’s PV=nRT.  I’m interested in a couple of things about oxygen:

A mole of oxygen (if you don’t remember what a mole is, look it up) masses 16 grams and occupies 22.4 liters at standard temperature and pressure (273.15 degrees Kelvin, or zero degrees Celsius, at a pressure of 1 bar).  Units don’t matter so much since we’ll be working with proportions.  I live in Denver at 6,000 feet where the pressure averages 0.81 bar and normally work around 72 degrees Fahrenheit, or 295 degrees Kelvin.  The math is simple proportions from that point on:  22.4 liters*295/273 *1/.81.  This works out to 30 liters per mole, closely enough, or 30 liters per 16 grams of O2.

To achieve 1 ppm, or 1 mg/l, of oxygen in a 20 liter batch (about 5 gallons plus one quart, close enough for homebrew) I need 20 mg of oxygen.  Converting that to liters, multiply by 30 liters per mole, divide by 16,000 mg/mole.  That gives 0.0375 liters.  At a flow rate of 32 minutes/liter, that gives me a requirement of 1.2 minutes of flow to achieve 1 ppm of O2 in solution at a flow rate of 1/32 LPM.  For 8 ppm, I’d need 9.6 minutes, rounded up to 10 because the transfer process isn’t perfect.  I could do it in 5 by upping the flow to 1/16 LPM but at risk of losing more oxygen to air.  May try it if I’m ever in a hurry.

Never thought that high-school chemistry would come in handy, did you?

For reference, at sea level, a minute at that flow rate is enough to get you 1 ppm.

Brew Day: Dusseldorfer Altbier

Lots of peace and quiet in the basement, and an uneventful brew day.  Leads us to an ancient brewer’s curse:

May your brew day be exciting.

Lots to be said for a boring brew day with no equipment malfunctions, no missing ingredients, nothing wrong with anything and even, unheard of here in Colorado, no wind to fight with.  Peace is a wonderful thing.  Brewing in the zone is zen.

A couple of process changes:  I did First-Wort Hopping for the beer.  I want bitterness but no harshness so I went with the old German way of hopping.  Nothing new there but during the lauter, I put the kettle on a hot plate turned up to full.  This kept the wort at or above 175 degrees and should have bound more hop acids to sugars, giving me more of the good stuff from the hops.  Time will tell.  Second in my drive to drive harshness from my beers was mash capping.

To cap a mash, you add crystals and dark malts at sparge or second runnings.  I did this with the CaraVienne and Blackprinz.  The result was a beautiful wort, about exactly the right color, but the roasted and crystal grains in minimal contact with water.  Should make for a smoother beer.  Again, I’ll report in about two months – the Altbier, while an ale, needs to cool condition for a while.

Tools You Need: A finishing Hydrometer

Ever take a hydrometer reading with your standard triple-scale and wonder if you were reading 1.012 or 1.014 or something in between?  After a bottle bomb and several over-carbonated beers, I got rather tired of guessing if the beer was finished or not, went out and spent 20 dollars on a tool to prevent the problem, a finishing hydrometer.


The scale runs from 1.020 to 0.980 in one degree increments.  That should cover nearly every beer and wine unless it’s either very thick or very highly attenuated.  The scale is extremely easy to read.  With it, you can tell very easily if the beer is finished or still fermenting.  The graduations are far enough apart you can even estimate a half-degree of specific gravity. Its only downsides as far as I can tell are a sample takes just as much as a regular hydrometer – about 4 ounces – and the instrument is very delicate.

Nosy’s evaluation of this piece of gear:  Worth the money.

Helles Update

I checked again tonight.  No more fermentation, gravity settled around 1.009, taste is dry and nice.  So much for my imagined diacetyl and a warning:  Last night I was sure the beer was history.  So I found something.  It has a bit of an estery character, not much at all and possibly the result of a few days fermenting at 76 degrees – my basement’s ambient temperature this time of year here.  But in my certainty that the beer was going bad, I found what I expected.  This is a lesson to me and to all brewers:  Appearance matters.  If your beer is clear and bright and nicely colored, a judge or consumer is going to expect it to taste good.  As will you.  So a key to brewing is to get the appearance right.

The beer is back in my lagering fridge for a quick crash of the yeast, then bottling in time for serving at the Oktoberfest party on October 3rd.

How to Tell Your Helles is Toast

I find myself in a bit of a jam.  I brewed a Helles for an Oktoberfest party coming up in less than a month.  Got it chilled, got it lagering, took it out of lager to warm up for bottling, everything fine, right?  Then it starts bubbling again.  Slowly, but bubbling, the gravity starts to drop from 1.012 to 1.007.  Now I’m getting the dreaded hint of cheddar cheese.  I’m not used to beers failing for sanitation but I guess it’s inevitable.  Brew long enough and some bug will get into the beer and set up shop.

I’ll let it go and see what happens but I don’t think I’ll be serving this in October.  I have a Schwarzbier that may be ready by then.  But to supply the party, I may be buying beer.  Haven’t done that in years.