Category Archives: Laboratory

This is a category reserved for items related to my published lab experiments, though the category name should speak for itself.

Temperature Data, Part I

Johnson Controls A19AAT-2C

I brewed a pumpkin ale on October 5 and have had it in an old refrigerator controlled by a Johnson Controls A19AAT-2C thermostat ever since.  I finally got around to installing two digital temperature sensors a couple of days ago: one inside the fridge and one hanging outside to measure ambient temperature.  Now that a full 24-hour period has passed, I have some data!

Using a simple spreadsheet program, I graphed the temperature data for yesterday.  I’m interested to see how far the temperature fluctuates given the ambient temperature and how well the Johnson Controls thermostat works.

I already see one problem: it’s Autumn here in South Georgia, and the outdoor temperatures vary from below to above the ideal ale fermentation temperature nearly every day.  The thermostat only tells my refrigerator when to turn on, and can’t do anything when the temperature is too low.  I’m searching for a heater now…


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Extract to Grain Conversion

Last night I was putting together a new recipe for this year’s Pumpkin AleBack in 2012 I made a decent one with dried malt extract, but since I’ve stepped up to all-grain brewing I need to convert the recipe from extract to all-grain.  I came across this old article at BYO on converting an amount of extract to an equivalent amount of grain, and there’s a technical aspect of this that I like. It goes something like this:

A pound of dried malt extract (DME) brings a gallon of water to a specific gravity of 1.045.  That, we say, is 45 points.  One pound of the 2-row grains I intend to use will bring a gallon of water to 1.036 SG, equalling 36 points, but only at 100% efficiency.  Assuming my home brewery will only get 75% efficiency, I will get 75% of those 36 points, which is 27.

Stay with me here…

We divide those two values (the DME points and the grain points) to get a percentage of points that the DME has over the grains:

45/27 ≈ 1.67

My original recipe calls for 3 pounds of DME, which when multiplied by 1.67 is 5.01.  This means I will need 5.01 pounds of grain to get the equivalent amount of fermentables I would have with 3 pounds of DME.

While I enjoy all the math and science that brewing lends I can’t help but sit back and say to myself, “Dude…  You’re making homebrew.  It’s supposed to be fun – not rocket science.”

And I say “self, I agree.”  There is some interesting fun with trying the math, but realistically there is no way (in my home brewery) to accurately gauge mash efficiency.  Hell – I might be doing something accidentally right to get 89%, but who knows?  Even if I sweat over the details and get exact measurements of grain according to the formula output, I’ll never really know if my all-grain batch came out just the same as the extract.  In all likelihood the product will be good and at least similar to the extract batch, and the details won’t keep me up at night.

Those kinds of details matter to professional brewers, but I doubt they use malt extracts in their pilot systems.

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DraughtKeg Disassembly

The Story

My family has four refrigerators.  One obviously in the kitchen, one I bought for my computer shop, one in my wife’s classroom, and one tiny fridge I picked up for $25 to put my lunch in at work.  I had this tiny refrigerator in my office for a couple of years and decided to take my shop fridge to work because it’s bigger.  Now I have this small and nearly useless fridge in my house with few ideas about what to do with it.

The DraughtKeg is a proprietary 5-liter package of beer that appears to be from Heineken and is pressurized with an internal CO2 cartridge.  It comes with a few plastic pieces used to serve beer directly from the keg, but it is also compatible with the Krupps BeerTender appliance.  There are several other brands of beer available in DraughtKegs, but I’ve only seen Heineken, Heineken Light, and Newcastle Brown Ale with my own eyes.  I’ve noticed the DraughtKeg in stores for a while now, but since my mind has been on kegging homebrew lately I wondered if the keg itself could be reused for kegging homebrew.  It turns out that it’s not, but if you ever wondered what’s inside one of these you don’t have to spend your own $20 on one to find out.

The Disassembly

I purchased this DraughtKeg at my local Publix supermarket and spent a couple of days emptying it.  Five liters is 14.09 twelve-ounce servings; I think it took four days or so.  When it finally tapped out, I grabbed the camera and some tools.  The only thing stopping a project to reuse the keg is the internal CO2 cartridge.  It can’t be removed through the 1″ hole in the top.  It is also glued to the bottom, which would make sanitizing the keg quite tedious if not impossible.  The slideshow below will walk you through disassembly:


While the DraughtKeg is convenient, it’s not eco-friendly.  It’s made of recyclable steel – which is perfectly fine – but it would be nice if it were refillable.  I’m not asking them to change it, but I’m not encouraged to buy another one.  My next bit of research for this little endeavor involves a 2.5-Gallon Cornelius Keg, but that may be too big for my tiny fridge.  We’ll see.

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