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Steamboat Stagger

webmaster — Tue, 17 Aug 2010 16:07:26 +0000

Yeah, well, let’s see how you do at 6800 ft.

Name: Steamboat
Date: Aug 17, 2010 9:08 am
Map: View on Map
Distance: 2.05 miles
Elapsed Time: 19:24.8
Avg Speed: 6.3 mph
Max Speed: 7.4 mph
Avg Pace: 09′ 28″ per mile
Min Altitude: 6,698 ft
Max Altitude: 6,798 ft

Ten Deliveries

webmaster — Mon, 14 Jun 2010 04:24:12 +0000

What’s the point of having GPS on your iPhone if you aren’t going to geek out about stuff?

Name:    13 June 2010
Date:    Jun 13, 2010 6:17 pm
Map:    Google Maps
Distance:    48.3 miles
Elapsed Time:    1:50:30
Avg Speed:    26.2 mph
Max Speed:    55.1 mph
Avg Pace:    02′ 17″ per mile
Min Altitude:    656 ft
Max Altitude:    819 ft
Start Time:    2010-06-13T22:17:01Z

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Refractometer Estimates of Final Gravity

webmaster — Sat, 12 Jun 2010 01:05:27 +0000

A refractometer is one of the most useful tools a brewer can have. It allows for near-instantaneous measurements of specific gravity, without having to compensate for or adjust sample temperature or withdraw a large volume of wort/beer (a significant concern at homebrew scales). There are a few issues associated with accurately using a refractometer for brewing, though. First, a refractometer does not actually measure specific gravity, or sugar content. Instead it simply projects a line through a reticle, and relies on the fact that the refractive index of the fluid will move a line up and down the reticle. For a simple sucrose solution (the refractometers common to homebrewers are “borrowed” from the wine industry) the refractive index depends only on the sugar content and the temperature. Automatic temperature correcting (ATC) refractometers use a bimetal strip to cancel out the temperature variable (within a given range), meaning that the reticle can be marked directly in units of sugar content. Brewers’ wort, however, is not a sucrose solution, and so a “wort correction factor” must be applied. Generally this is done by dividing the refractometer reading by 1.04.

The second, more intractable problem with using a refractometer to determine specific gravity is that once fermentation begins, the beer becomes a three-part solution: sugars, water, and alcohol. There is no longer fidelity of measurement – that is to say, there can be more than one specific gravity that will correlate to the same refractive index. Generally speaking, however, only one of the potential data points will be sensible for a real beer. Making that assumption, it should be possible to develop a correlation between the measured refractive index and the actual gravity of the beer, as long as the alcohol content can be estimated. This means that if both pre- and post-fermentation readings are taken, the FG can be predicted. Various software packages and websites incorporate tools to do just that, all of which seem to use the same correlation:

FG = 1.001843 – 0.002318474*RI_i – 0.000007775*RI_i² – 0.000000034*RI_i³ + 0.00574*RI_f + 0.00003344*RI_f² + 0.000000086*RI_f³

Where RI_i and RI_f are the initial and final refractive indices, respectively, in wort-corrected degrees Brix.

I took pre- and post-fermentation readings of ten beers, with OGs ranging from 1.036 to 1.103, using both a refractometer and hydrometer. In every case the refractometer correlation provided an FG that was lower than the hydrometer reading, by anywhere from 0.5 to 8.5 “gravity points” (1000*(SG-1)). The mean discrepancy is 5.1 points. The main variable of concern seems to be the attenuation of the beer; the greater the attenuation, the larger the discrepancy. The results are plotted below.

Note that the discrepancy is zero at about 58% attenuation (71% apparent attenuation). I have no information on who originally developed the correlation, but my supposition is that they only tested worts with about this degree of fermentability. A logarithmic curvefit provides a reasonably good (R² ≅ 0.7) approximation for the offset that is needed; by adding this correction factor to the standard correlation, the maximum discrepancy for this dataset is reduced to only 2.1 points, and the average to 0.1 points. Unfortunately, the resulting equation is a bit unwieldy:

FG = (1.001843 – 0.002318474*RI_i – 0.000007775*RI_i² – 0.000000034*RI_i³ + 0.00574*RI_f + 0.00003344*RI_f² + 0.000000086*RI_f³) + 0.0216*LN(1 – (0.1808*(668.72*(1.000898 + 0.003859118*RI_i + 0.00001370735*RI_i² + 0.00000003742517*RI_i³) – 463.37 – 205.347*(1.000898 + 0.003859118*RI_i + 0.00001370735*RI_i² + 0.00000003742517*RI_i³)²) + 0.8192*(668.72*(1.001843 – 0.002318474*RI_i – 0.000007775*RI_i² – 0.000000034*RI_i³ + 0.00574*RI_f + 0.00003344*RI_f² + 0.000000086*RI_f³) – 463.37 – 205.347*(1.001843 – 0.002318474*RI_i – 0.000007775*RI_i² – 0.000000034*RI_i³ + 0.00574*RI_f + 0.00003344*RI_f² + 0.000000086*RI_f³)²))/(668.72*(1.000898 + 0.003859118*RI_i + 0.00001370735*RI_i² + 0.00000003742517*RI_i³) – 463.37 – 205.347*(1.000898 + 0.003859118*RI_i + 0.00001370735*RI_i² + 0.00000003742517*RI_i³)²)) + 0.0116

In order to spare anyone who might be interested some trouble, I’ve put together a simple spreadsheet that will calculate FG using both the old and new correlations, in addition to attenuation and ABV. If you end up using it for a significant number of batches, please share your results.

Update: 20 July 2010

I’ve since refined the FG correlation, using a more mathematically rigorous method. I leave the original post up for transparency’s sake, but if you’re looking for an FG calculator, please check out the new post.

Spreadsheet download:
fg_calculator.ods | fg_calculator.xls

Thermometer Calibration

webmaster — Mon, 24 May 2010 20:22:41 +0000

It’s spring cleaning time in the brewery. I’ve given the kegerator a good once-over, scrubbed the kettles shiny, replaced all the vinyl tubing, and so now it must be time for instrument calibrations. I check the hydrometer and refractometer every few batches because it’s so easy (use water and a 10% sucrose solution), but it occurred to me that I’ve never checked my thermometers. There are seven types that get regular use in my brewery:

My newest toy – a NIST-traceable waterproof digital probe model
A TruTemp-branded compact digital that set me back about $9
An AcuRite-branded digital “meat” thermometer
A no-brand kitchen probe thermometer from Walmart
An ordinary floating alcohol thermometer
Several LCD strip thermometers
The bulkhead thermometer in my boil kettle

Since the kettle thermometer requires about three gallons, and the strips five gallons, of liquid in order to be submerged, it didn’t really seem practical to check them against the others. All the others read to 0.1°C, except for the AcuRite (1°C) and the Walmart thermometer, which only does Fahrenheit and which I know not to be accurate anyway.

The other five thermometers were checked at four temperatures: 0.0°C (ice water), ~23°C (room temperature), ~59°C (mixture of ice-cold and boiling water), and 99.2°C (boiling water). That gives me, roughly speaking, fermentation and mash temperature calibrations for each, plus a couple of outliers for pretty curve fits. For the two middle values, the traceable thermometer’s readings were assumed to be correct, which given the readings at freezing and boiling seems justifiable.

Generally speaking, all the thermometers did well. Throwing out the no-name Walmart model and the surprisingly inaccurate alcohol thermometer, the maximum variation was 1.3°C, which isn’t great for lab equipment but is probably fine for brewing. Surprisingly, the AcuRite kitchen thermometer is every bit as accurate as the ISO 17025-calibrated lab thermometer, landing all four readings within its (admittedly larger) resolution. The TruTemp model turned out to be less accurate, albeit with a highly linear discrepancy. This is interesting because it could point to a design problem – assuming a linear voltage response for the thermocouple rather than doing a multi-point calibration. More to the point, it means that it can still be useful for brewing once the proper offset is applied.

Way to Go, Steve-o

webmaster — Thu, 29 Apr 2010 19:58:24 +0000

Why does Apple only stand up and say, “this is what we’re doing, and this is why” every year or two? When they do, it usually makes the hairs on the back of my neck stand up.

Thoughts on Flash

Flash was created during the PC era – for PCs and mice. Flash is a successful business for Adobe, and we can understand why they want to push it beyond PCs. But the mobile era is about low power devices, touch interfaces and open web standards – all areas where Flash falls short.

Build a Better Stirplate

webmaster — Mon, 26 Apr 2010 05:35:24 +0000

It probably isn't necessary to stir Iodophor.

OK, so the world probably won’t be beating a path to my door. But there’s a right way to do it, and a wrong way – and a lot of home brewers are doing it the wrong way.

The basic idea behind these homebrew stirplates is to control the speed of a motor (computer case fans being a cheap and accessible source) by varying the supply voltage. The best way to do it would actually be using pulse width modulation via a microcontroller, but I didn’t have one on hand, and energy efficiency probably isn’t a major concern for most people interested in powering a motor drawing around a couple watts. The simplest way to provide voltage adjustment (though not regulation, which I’ll get to in a second) is simply to put a resistor in series with the motor, which is what a lot of home brewers do. The problem with that (aside from the engineer in me hating the kludginess) is that electronic components are sold on profit margins more frequently associated with Wal-Mart stores, and are therefore made of plastic. If you have one lying around, or pick one up at Radio Shack, it will typically be rated 0.5 W, sometimes less. We’re going to be sinking around 12 V • 150 mA = 1.8 W into it. It will melt.

So, the bare minimum takeaway here is to use a potentiometer rated for at least 2 W continuous power. A better, or at least more elegant, solution is to incorporate some actual voltage regulation. Which brings us to one of the most useful components ever invented, the LM317 adjustable voltage regulator. The LM317 is capable of providing anything from 1.25 to (V_in – 1.7) V with good regulation (±1%), using only two resistors to set the output voltage:

V_out = 1.25(1 + R₂/R₁)

The basic schematic for the LM317. Note the potential problem with the value of R1.

Replace R2 with a potentiometer and you have a nifty little 1.5 A adjustable power supply using only three components. A couple filter capacitors probably aren’t necessary for our purposes, but they’re cheap insurance. The only downside to the LM317 as a regulator is that it’s inefficient; any excess current is dissipated in the regulator as heat. Again, that could be up to 1.8 W in this application. The most common regulator package is a TO-220, which can only safely dissipate around 1.5 W. So a heat sink is definitely a good idea. The LM317 has a built-in thermal shutdown, though, so you might be able to get away without a heat sink if you’re careful not to run the fan at very low speeds. If you do sink it, be aware that the tab on the TO-220 package is tied to V_out – so be careful to avoid shorts. In the photo of the internals, you can see that I sealed the heat sink bolt with heat shrink tubing just to be safe.

Technically, an LM317 can have a minimum load current as high as 10 mA, although most will be much lower. That puts the maximum value of R1 at about 120 Ω (10.4 mA). Note that the datasheet specifies 240 Ω because it’s lifted from the specs for the LM117, which tops out at 5 mA. It’s also worth noting that I’m using a 220 Ω resistor simply because I had a 2.5 kΩ pot and didn’t feel like buying another. Do as I say, not as I do.

Circuitry aside, the rest of the build is pretty easy. I had a plastic kitchen container that happens to be the perfect size for my 1 gallon starter jugs. I bought a pair of neodymium rare earth magnets, which are simply adhered magnetically to the hub of the case fan. At 4 pounds of lift each, they aren’t going anywhere. If the fan was attached directly to the container, the magnets would make contact with its surface, so you’ll need some sort of spacer. I used roughly 5 mm lengths cut from a plastic drinking straw. The magnets and the power supply both came from American Science and Surplus, and the only other thing I needed to buy was a stir bar: $6 on eBay. If you’re going to use your stirplate with a convex-bottomed vessel, it might be worth noting the type of stir bar that works for me. It’s 1″ x 3/8″ with a ring.

The stirplate internals. Blue LEDs optional but awesome.

The complete parts list would be:

Project box or other plastic container
12 VDC power supply (at least 300 mA to allow for power spikes on startup)
PC case fan
Mounting hardware for fan
LM317T
TO-220 heat sink
120 Ω resistor
1 kΩ potentiometer
Knob for potentiometer
0.1 μF ceramic disc capacitor
1 μF electrolytic capacitor
2 rare earth magnets
Magnetic stir bar

Plus wire, solder, perf board, etc. If you’re a tinkerer you probably already have some of this stuff on hand. Even if you had to buy everything online and pay shipping, it would only cost about $30. Tayda Electronics is a great source for components. Avoid Radio Shack like the plague.

Now that I’ve gotten off my lazy ass and put this thing together, I’ll be updating my aeration experiments with one last trial, to test my assertion that frequent shaking and a stirplate are equivalent.

Sunday Runday

webmaster — Sun, 18 Apr 2010 18:50:17 +0000

Now that my endurance is (nearly) where I want it, I’m trying to build in some pacing work. This is a course record for me.

Name:    5K
Date:    Apr 18, 2010 1:36 pm
Map:    Google Maps
Distance:    3.30 miles
Elapsed Time:    26:41.5
Avg Speed:    7.4 mph
Max Speed:    7.6 mph
Avg Pace:     08′ 06″ per mile
Min Altitude:    679 ft
Max Altitude:    797 ft

It’s the Little Fittings

webmaster — Fri, 16 Apr 2010 18:57:32 +0000

I know, my kettle is filthy...

When I moved off the stove several years ago, I picked up a cheap stainless steel kettle on eBay. It’s only 8.5 gallons, but it had a thermometer and ball valve installed, and the price was right – $99. The only downside was that it had the pipe nipple installed about ¾” off the bottom, meaning that for the past forty-odd batches, I’ve been leaving roughly half a gallon behind when transferring to the fermenter. I’d always planned to put in some sort of pickup tube, but since there was so little thread available, and so little room between the nipple and the bottom, I figured I’d either need to solder it, or use some bulky and expensive kludge. So that project was always on the back burner, if you’ll pardon the pun.

Then yesterday, while doing a whirlpool addition of cardamom to a tripel, one of the seed pods got sucked through the pump and clogged my chiller. Enough was enough. I ran to the hardware store and bought every brass pipe fitting known to man, thinking I’d be able to hack together something. Turns out all I needed was a single 90° female fitting. One of my concerns proved valid – there’s just barely enough thread for it to grip, and in the proper orientation it can’t be fully tightened – but it’s a perfect fit, sitting just a couple millimeters off the bottom, and apparently the threads are tight enough for the pump to pull a vacuum. I did a “dry run” (pun lovers are really getting their money’s worth today!) and it seems like my kettle dead space is now about 100 mL. Yay.

Truti Fruiti recipe (PDF)

Yeast Ranching and You

webmaster — Tue, 23 Mar 2010 16:38:09 +0000

With all the writing I’ve been doing about yeast lately, I thought it would probably be a good idea to outline my general yeast propagation and storage procedures. There’s an enormous variation, both philosophically and technically, among homebrewers – from directly pitching a smack pack to acid washing and storage in -80°C freezers. My own techniques are based on two sometimes contradictory goals:

Emulate professional brewers’ procedures whenever possible, in an endless pursuit of better beer.
Minimize the expense of brewing, in terms of both time and money.

#1 precludes simply throwing in a smack pack and hoping for the best, and #2 precludes buying new yeast every time I brew. So I find myself a reluctant yeast rancher. There are many ways of storing yeast, and all of them have been tried by other home brewers at one time or another, so I’m not going to go into details here. Suffice it to say that the cheapest and easiest is to store yeast slurries in an ordinary refrigerator. If you’re going to be using the yeast within a few weeks, you can even harvest it directly from the fermenter and re-pitch into the next batch. I don’t really brew often enough for that to be practical, and I also worry about the strain of repeated high-gravity fermentations causing mutations, so I propagate solely in un-hopped 1.030 starter wort. In effect, this means I’m always pitching first-generation yeast, although I’ll probably start over every few dozen batches anyway, just for peace of mind.

Except for when I’m starting a new strain from a smack pack, the cycle begins and ends with a 100 mL glass jar that’s stored in my beer fridge. It’s pretty important to get a reasonable estimate of the number of cells in the starting population; any errors here will be compounded throughout the rest of the process. For the sake of simplicity, I’m going to assume the slurry is a cylinder 3 mm in height and 6 cm in diameter. It’s almost exactly a month old, so the viability should be about 75%. Assuming a density of 4.5 billion/mL, there should therefore be about: π(3 cm)²(0.3 cm)(4.5 billion/mL)(0.75) = 29 billion viable cells. That’s enough that I’m going to step up only twice. For an older slurry (fewer than about 10 billion cells), I would do a three-stage propagation.

Unless poor planning or a heavy brewing schedule have drained my supply, I do all my propagations using the tail runnings from a previous mash that I store in the freezer. This is the ultimate cost-cutting measure; as I continue to use a particular strain, the yeast cost per batch approaches zero. These particular tail runnings are from a doppelbock, so they’re darker than usual. Since I’m going to be decanting the starters, that isn’t a huge issue – and this is being pitched into a stout anyway. For a very light beer I would have to plan ahead, or bite the bullet and buy some DME. They’re also higher-gravity than usual, at about 7°P (1.028). Ordinarily the tail runnings would end up closer to 3-5°P (1.012-1.020) and need to be boiled down by about half.

For the first stage I’m going to use 500 mL. (When building up from an older slurry I would start with 200 mL, then 500.) The chief drawback to using the MrMalty calculator for this kind of thing is that it won’t deal with starter volumes smaller than 1 L – presumably because that’s roughly the minimum size needed to get significant growth out of a smack pack. So for the first stage, I use the Wyeast calculator instead. As you can see, it predicts that my 500 mL starter will produce about 137 million cells/mL, or 68 billion total. So it’s basically back up to the cell count of a smack pack.

Now I can move back to the MrMalty calculator, manually setting the viability to 68%. For this particular beer, I therefore need roughly a 2.5 L starter. I’m using the “continuous aeration” setting, not because I am aerating continuously – only as much as foaming allows – but because that’s the setting that most closely matches my own slurry measurements, adjusted for 1.030 wort. My highly sophisticated aeration setup consists of an “Elite 800″ model aquarium air pump, with two 0.45 μm syringe filters in series, and a disposable plastic air stone. I like the disposable stones because they produce very fine bubbles, and can be thrown away instead of trying to sanitize the microscopic pores. The stainless steel nut is there to keep the air stone from floating to the top of the starter.

Be sure to allow enough time – 3-4 days per stage – to have the yeast ready by brew day. After each stage, I refrigerate the starter overnight, then decant as much liquid as possible, both to remove the alcohol and to maximize the surface:volume ratio. The whole idea here is to keep the yeast as healthy as possible, and avoid any potential long-term complications. Before cooling the final stage, though, I resuspend the yeast and pour off 100 mL of the starter into a jar. This keeps a protective layer of beer over the yeast for storage, and ensures you won’t select a substantial number of mutants that are either more or less flocculent than the population as a whole. The jar is then sealed, labeled with the strain, number of “generations”, and the date, and placed in the fridge for next time. Yeast stored this way can be revived and built back up to a pitchable population after well over a year.

Because I know you’re curious, the yeasts I’m currently keeping on hand are:

Wyeast 1028 London Ale (Worthington White Shield)
Wyeast 1056 American Ale (Sierra Nevada)
Wyeast 1084 Irish Ale (Guinness)
Wyeast 1272 American Ale II (Anchor Liberty)
Wyeast 2035 American Lager (August Schell)
Wyeast 2206 Bavarian Lager (Weihenstephan 206)
Wyeast 3787 Trappist High Gravity (Westmalle)
Wyeast 3864 Canadian/Belgian Ale (Unibroue)
Wyeast 3944 Belgian Witbier (Celis White)

With these nine strains I feel I can brew just about anything (at least anything I brew regularly), without having two that would be substantially similar.

Crescent Crawl

webmaster — Mon, 22 Feb 2010 00:53:09 +0000

Name: NOLA
Date: Feb 21, 2010 6:01 pm
Distance: 3.86 miles
Elapsed Time: 40:08.1
Avg Speed: 5.8 mph
Max Speed: 12.0 mph
Avg Pace: 10′ 24″ per mile
Min Altitude: 33 ft
Max Altitude: 108 ft

Click on this link to display the track in Google Maps. This link will be valid until Mar 23, 2010 5:47 PM PDT.