SeanTerrill.com » toys

Toys for Watts

webmaster — Tue, 13 Mar 2012 20:29:06 +0000

Get it? It’s a thermodynamics pun! How many brewing blogs give you wordplay like that? None of the reputable ones, that’s for sure.

Anyway… Last year I started experimenting with partial boils, due to not being able to use a garden hose in the winter. And that technique has been working well for me, though it has some limitations. It would result in an unworkably thick mash when brewing a big beer, for example. More importantly, I anticipate brewing a lot of test batches for Two Mile in the near future, and there’s always the possibility that some unforeseen flavor impact could rear its ugly head.

But even during one of the driest winters on record, the one thing Silverton has in abundance is snow. Sticking the kettle into a snow bank isn’t going to do much (snow being one of nature’s great insulators), but melting some of that snow is going to make a hell of a heat sink. So I have a new toy, a Little Giant water pump. It’s rated 63 gallons per hour at one foot of lift, which turns out to be a little less than I’d like for a five-gallon batch – it took 60 minutes to chill 5.75 gal of wort from 92°C to 11°C. The majority of the chilling was done in the first 20 minutes, though, so I consider that acceptable. Next time around I’ll try to position the heat exchanger so that the pump is fighting a little less static head. If I can get the kinks worked out this may become my standard wort chilling technique, at least during the nine months of the year there’s snow on the ground.

Reverse Mashing 2

webmaster — Sat, 15 Oct 2011 22:28:45 +0000

Background

Last time I toyed with the idea of “reverse mashing”, I found that an unheated kitchen isn’t a great place to do mashing experiments in the winter. Fortunately, I have a new toy available in the form of an oven with a “Warm” (170°F – 77°C) setting, and so I was able to perform two additional mashes utilizing longer rests.

Experimental Setup

For details on how the experiment was conducted, refer to the first post on the subject. Once again, the reverse mash was performed first, to determine the overall length of both mashes. Total time was 100 minutes, and the temperature profiles for all four mashes are shown below.

All other variables were kept constant between the two sets of mashes, with the exceptions of size and fermentation temperature. Since I needed starter wort for some upcoming brewing, I doubled the size of the mashes, to 1000 g of grain each. Fermentation took place in my new fermentation chamber, with the air temperature set for 20°C ± 1°C. The test worts were allowed to ferment for six days, then rested for one day at 8°C before gravity readings were taken.

Results

The reverse mash fermented from 12.0°P to 1.0093 SG, and the control from 12.4°P to 1.0068. As expected, the conventional step mash exhibited both higher efficiency and higher attenuation than the reverse mash. While the efficiency values for both new mashes are significantly improved, however, the attenuation values are similar. While increasing mash efficiency is desirable in most situations, home brewers may well find that a very short step mash provides fermentability on par with a more conventional longer mash, and that the time savings outweigh their comparatively modest financial investment. In a commercial brewing setting, however, the traditional lengthy mash with α- and β-amylase rests is clearly the better option.

Pass Creek Trail

webmaster — Sun, 21 Aug 2011 17:14:28 +0000

Thursday, I was able to get away from the brewery a little early, so I finally managed to get in a hike I’ve been trying to do all summer. Pass Creek Trail runs from Coal Bank Pass up to join the Colorado Trail. From the junction, there’s a quick but treacherous spur that runs most of the way up Engineer Mountain. A trail guide will probably rate the trail “Moderate-Difficult” or somesuch, but don’t be fooled – excepting the last quarter-mile, the trail is wide, well-maintained, and only a gradual (albeit continuous) climb. And compared to Rysy, which will probably forever be my benchmark for difficult hikes, even the summit is a walk in the park.

The peak itself was probably blocking a few satellites once I got near the top. While the trailhead elevation is two feet off of the published value, a look at the topo map confirms that I ran out of handholds at roughly 12,500 ft, about 500 ft below the summit. Getting accurate and timely elevation fixes continues to be a problem. I don’t know if that’s a function of the iPhone GPS chipset, the software, or both.

Name: Pass Creek Trail
Date: Aug 18, 2011 5:08 pm
Map: View on Map
Distance: 3.29 miles
Elapsed Time: 2:13:11
Avg Speed: 1.5 mph
Max Speed: 7.0 mph
Avg Pace: 40′ 26″ per mile
Min Altitude: 10,638 ft
Max Altitude: 11,864 ft

It’s the Little Fittings Too

webmaster — Wed, 13 Oct 2010 02:55:20 +0000

In preparation for my move to the Great White, um, West, I’m brewing two batches this week. First up: a Westvleteren 12 clone. (Rant: In “Belgian degrees”, wouldn’t 12° correspond to about 28°P? It should be called Westvleteren 9°! But I digress.) Stay tuned for an updated porter recipe on Friday.

Good news! It gave me a chance to snap a couple quick shots of my latest invention. Even after implementing my brilliant kettle draining apparatus, I was getting sick of worrying about all the trub getting sucked through the pump – not because I think the pump can’t handle it, but because I worry about crud providing a hiding place for contaminants. Enter the world’s cheapest tubing bender, and a simple length of copper tubing.

So, back to the beer. I overshot my gravity slightly and came in at 22.9°P (1.096). Operator error, really: I forgot that about 13% of the fermentables are coming from the sugar, and based my efficiency estimate on a 1.092 OG, instead of 1.080. My B. Otherwise, the day was completely uneventful, even boring. Not a good portent for my brewing career if I’m only interested when something goes wrong.

Westy 12 recipe (PDF)

The Future Is Gonna Be Incredible

webmaster — Fri, 24 Sep 2010 17:07:35 +0000

Or more sinisterly, who is safe from the man who controls a swarm of nanites with his thoughts? Snow Crash meets The Diamond Age.

BBR Interview 3

webmaster — Tue, 14 Sep 2010 00:25:26 +0000

James Spencer and I did another interview for Basic Brewing Radio, and this time it was even in person, which was a lot of fun. It deals with gravity measurements and some of the intricacies of using refractometers, and concludes with a call for additional data that will hopefully corroborate my final gravity correlation.

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

View Larger Map

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.

Update: 07 Apr 2011

I’ve tweaked the correlation and posted some results from other brewers, as well as an updated spreadsheet: Refractometer FG Results

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.