The Latest

No, there’s nothing wrong with the Earth’s gravity, I’m only referring to Specific Gravity, the ratio of the density of a liquid to the density of water. In this case, the specific gravity I’m concerned with is the specific gravity of my two fermenting batches of beer.

The alcohol content of beer can be calculated based on two measurements of the beer’s specific gravity. The first, called Original Gravity (OG) is measured before fermentation starts. The last, called Final Gravity (FG) is generally taken at bottling or kegging time. Between these a brewer can of course take interim measurements. The reason for the change in specific gravity is that the amount of dissolved sugar in the beer at the start of fermentation makes for a higher density liquid than water, but as the yeast converts sugar into low-density alcohol, the density of the beer drops.

Basically, if the alcohol content at the start of fermentation is zero, then as the yeast creates alcohol the density of the beer drops accordingly, and a measurement of density makes it possible to estimate how much alcohol is present.

The alcohol content is estimated based on the difference between the original and final gravity measurements. I typically use software or a lookup table to estimate the alcohol content by volume (ABV) of my beer. The equations most software use are empirical and therefore approximate. I know of two, one simpler, and one more complex^[1].

1. ABV = (OG - FG) * 131.25
2. ABV = (76.08 * (OG - FG) / (1.775 - OG)) * (FG / 0.794)

Right now I have two 5 gallon batches fermenting. One is a Belgian Strong Golden Ale, which spent 3 weeks in the first fermenter, and has been in the second fermenter for about 3 weeks so far. The target time for secondary fermentation for this beer is approximately 2 months, so I’m still 5-6 weeks out from bottling unless I decide to bottle early.

The second batch is a simpler American-style (really, California-style) pale ale which is less complex. I expect to only do a single stage 4 to 5 week fermentation. This beer has been fermenting for 2 weeks so far.

Tonight I took interim gravity measurements of both beers to estimate how far along in the brewing process they are, and approximately how strong they will be when ready to drink. So far things appear to be going well, and I’m getting the itch to bottle these brews so I can start another.

Belgian Strong Golden Ale

Original Gravity (OG): 1.072
Gravity at transfer to secondary fermenter: 1.014
Gravity on April 14: 1.010

By the first equation, the percent alcohol by volume when I transferred it to the secondary fermenter was approximately 7.6%. By the second equation it was estimated at approximately 8.0%. As of today, the specific gravity has dropped further, to 1.010. By the first equation the beer is estimated to be about 8.1% alcohol, and by the second about 8.5%. Either way, this looks like it will be a very strong beer, and since it is so golden and used a Belgian yeast, I think Belgian Strong Golden is an apt description.

As part of the measuring the gravity of my beer I have to extract a sample. Some people sanitize all their equipment and return the sample to the fermenter, but I tend to only sanitize the thief^[2] used to extract the sample, and then drink it to gage how the flavor of the beer is developing. As of today, the Belgian ale is coming along nicely; it is pleasantly sweet with no off flavors. I’ll let it continue in the fermenter for a while longer, but I think it would be fine to bottle this before too long.

Pale Ale

Original Gravity (OG): 1.048
Gravity on April 14: 1.008

By the first equation, the percent alcohol of my pale ale is estimated to be about 5.3 percent. By the second equation, the alcohol content is also estimated to be about 5.3 percent. The beer is a very pretty pale golden, about what would be expected of the style.

As the fermentation is only two weeks in, it is expected that the beer is still a little rough around the edges. The sample I extracted for the measurements tasted generally good, but a bit watery and yet alcoholic. This could be a byproduct of higher than desired fermentation temperatures in the first two days of fermentation, but it may very well just be a young beer that needs a little more time to condition.

Right now I plan to bottle this brew at the end of April, and I’ll sample it again at that time. If the flavor seems good then, I’ll call it ready. If not, I’ll give it a couple more weeks.

— Steve

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1. I pulled the equations from one of many online brewing resources. In this case, Brewer’s Friend↩︎
2. A beer (or wine) thief. Basically a simple plastic tube to extract a sample of liquid from a fermenter. Some are based on creating a vacuum above the sample like mine (you stick it into the beer and let it fill, then cover a hole with your thumb like a straw), while others use a simple gravity based one-way valve.↩︎

Way back in January I wrote about getting my road bike tuned up for the season. Shortly after that we got a huge snowstorm that delayed my plans, and then I started riding my fixed gear bike instead.

As a result my good geared road bike sat about halfway put together for almost 2 months. At the end of March though I finished my mash tun project and while I was in a project mood tackled the road bike too.

I set up my work stand at the top of the driveway and cleaned and greased everything that still needed it. I reinstalled the cranks and put the new chain on. I finished adjusting the brakes, adjusted the derailers, and bent the front derailer cage slightly to accommodate the slightly shorter spindle in the new bottom bracket. That bend probably only put it back where it should have been in the first place and it works better than ever.

After all the mechanical bits were ready I spent an hour or so nicely wrapping the bars in bright yellow tape, and then finished the tape off with tightly wrapped twine. It looks great.

I’ve been on two decent rides since, and it’s smoother than ever. Eventually I may do some more work on it, such as installing a new drivetrain and new wheels, but for now my trusty Trek is ready for another year or two.

— Steve

Overview

The other day I pulled out my old Coleman cooler, which hasn’t been used since I went to Burning Man in 2006. After talking with some brewing friends I decided to use it as a mash tun. Coolers, both round and rectangular, are popular for mash tuns because they are inexpensive, easy to build, and well insulated, so they allow you to maintain temperature for an hour-long mash without having to continually apply heat.

At first I wasn’t sure what size the cooler was, so I poured water in from 5 gallon pail. At 10 gallons the water level was right at the first break in the cooler wall, and at 15 gallons it was nearly up to the next step in the wall. Clearly this is a 70 quart cooler. The photo below shows approximately 15 gallons of water in the cooler.

I emptied the cooler and came up with approximate measurements.

• Length: 24 inches
• Depth: 10 inches
• Height: 12.5 inches to seal (highest step in the wall)

I removed the drain plug inexpertly with a pair of pliers and the hole measured approximately a 3/4 inches in diameter. I also inserted a short dowel I had laying around to check whether I needed to make any height adjustments to get the a copper manifold to lay flush at the bottom. Luckily it looked like the height of the hole was perfect.

There are several ways to create a good grain bed and allow the sweet wort out but leave all the grain and husks in the tun. These include mesh screens, false bottoms, braided steel lines, and copper manifolds. They all work in approximately the same way, but based on my measurements, the shape of the cooler, and the recommendations of my friend John, I decided to build a copper manifold.

Construction

After work on Friday I drove down to Home Depot to buy supplies. I bought 10 feet of 1/2 inch type M copper pipe (typical household pipe) and a bunch of 1/2 inch fittings. A parts list for the curious is enclosed.

• 10 feet of 1/2 inch copper
• 4 elbows
• 5 tees
• 1 female 1/2 inch MIP to sweat fitting adapter
• 1 1 inch long 1/2 inch MIP brass nipple (almost too short)
• 1 pack of #15 O-rings
• 1 gigantic washer
• 1 1/2 inch ball valve
• 1 1/2 inch MIP to 3/8 inch barb adapter
• 10 feet of braided nylon hose.

I only actually need about 1-2 feet of the hose, but it came in 10 foot sections and I figured additional hose might come in handy. I had to make a second trip because my initial parts list had a 2 inch long brass nipple, and that proved to be much too long. I also picked up a hacksaw on my second way through. In hindsight a proper pipe cutter would have been better.

I got the valve assembled into the cooler on Friday night, and got all the copper pipe cut to the right lengths. A test fit showed everything was expected to work perfectly.

On Saturday morning I started working again. I washed all the copper parts in PBW, and scrubbed off the glue that held the UPC tags on the fittings. After rinsing and drying, I reassembled the manifold and crimped each connection lightly with a pair of pliers. It holds together well but can still be disassembled. This thing is supposed to leak so there was no point in soldering anything.

I decided to cut the slits in the manifold using my knockoff Dremel and standard Dremel cutting wheels. Eye protection is critical for these things, people. The wheels have a bad tendency to shatter without notice. I lost 4 or 5 cutting wheels to breakage, and wore several more down to mere nubs. It took a while but I think the Dremel was the right tool for this. A hacksaw would have been a lot more physical labor.

After I finished cutting the slits I used a small grinding tool to grind the burrs off of each slit, and then a nylon brush wheel to clean up after. There was still a lot of copper dust inside the manifold. I shook as much out as I could, and tried to rinse it out by forcing water through it with a hose.

Testing

After that I assembled the whole tun and did some checks. I filled the cooler with about 15 gallons of hot tap water (and concluded that it really might be over-large). I added PBW to wash the tub interior. I then took the temperature and closed the lid for an hour.

During this time the outside of the cooler never got warm to the touch except at the narrow point where the valve attaches. The valve did not leak. The temperature at the start was a hair under 122. The temperature after an hour was a hair under 120. This seems pretty good to me, and I’m excited to try it out tomorrow when I brew.

— Steve