Technical Communications

Republished from BrewingTechniques' May/June 1994.

Warning: Kegs under Pressure

In regard to Martin Manning's article on modifying kegs for home brewing (March/April 1994), it must be noted that in all likelihood the keg will be under pressure when the home brewer gets it. New kegs are usually pressurized before leaving the factory, and - assuming that a legitimate source for used kegs is found - the pressure in used kegs can be considerable (keg beer is typically served at 10 psi, and the pressure rises at room temperature). This poses a serious hazard for anyone cutting into a keg.

The pressure can easily be bled from a Sankey keg by pushing in the ball in the valve. Likewise, Hoff-Stevens kegs can be bled with a nail or other narrow object pushed into the valve hole. Golden Gate requires a special tool or drilling (carefully) through the wooden bung.

-John Zanteson
Birmingham Brewing Co.
Birmingham, Alabama

Planispiral Wort Chiller

Many home brewers use an immersion-type chiller to cool wort to pitching temperatures. Immersion chillers do pose a few problems, however. One problem with the standard helical (spring shaped) chiller coil is the need to stir the wort during the chilling process for the wort to cool evenly. This necessitates removing the pot lid and exposing the cooling wort to airborne infection. Stirring also disturbs the settling break material, which can affect the clarity of the finished beer.

These problems can be circumvented by using a planispiral chiller design. A planispiral (flat spiral, like an electric stove burner) chiller positioned just below the surface of the wort effectively cools the top layer. This sets up convection currents as the cooled wort sinks to the bottom and warmer wort rises, eliminating the need to stir the wort for even cooling. In this way the break material is allowed to settle, and the lid need not be removed until chilling is complete.

Various methods may be used to suspend the coil in place. My own chiller is made of 25 ft of 1/4-in. o.d. copper tubing. The outermost coil is folded down to make a "foot" to support one end of the coil, and the other is suspended by the in/out tubes that bend over the lip of the kettle. A means of adjusting the height of the coil in the pot is beneficial, because it enables optimal positioning (just below the wort surface) for any final wort volume.

My technique is to remove the kettle from the heat, whirlpool the hot wort, let it sit for 10-20 min, then put the chiller in the kettle and chill the wort. Using this technique, I have found no need for kettle coagulants such as Irish moss, because virtually all of the hot break and much of the cold break settles out, and the cooled wort can be easily racked off the settled break material.

-Ed Hitchcock
Halifax, Nova Scotia

BruProbe Accuracy Misstated

I found your article in the March/April 1994 issue BrewingTechniques on building the BruProbe very interesting. Having built temperature sensors for myself and at work for measuring low-temperature superconductors, I believe there is a serious error in the article.

It states, "The hand-held readout indicates temperatures from 0 °F to 250 °F within 0.1 °F of accuracy." I think this line should have read "with 0.1 °F of resolution." This degree of accuracy is very hard to obtain; in fact, the sensor used (LM34) is not even capable of such.

From the data book, "The LM34 . . . provides typical accuracies of 1/2 °F at room temperature, and 11/2 °F over the full temperature range."

If I'm missing something obvious, please let me know. Also, I'd like to say I think the BruProbe is a great idea. Even with 11/2 °F of accuracy, I think it's plenty accurate for brewing purposes. Personally, I use a thermocouple probe (uncompensated) hooked to a digital voltmeter. It's good for about 1 °C (1.8 °F).

-Joseph Kral
Los Gatos, California

McIlvaine responds: As Mr. Kral points out, the word "accuracy" should, indeed, be replaced with "resolution" since the readout displays in 1 °F increments.

-Robert McIlvaine, Jr.
Brookline, New Hampshire

I am enthusiastic about Martin Manning's article on modifications for brewing vessels in the March/April 1994 issue (it immediately preceded my own article on the three-tiered gravity brewing system).

In retrospect, I wish that I had used Manning's modification instead of my own. Manning cut out a 12-in. circle in the top of the half keg, leaving the built-in handles, whereas I cut the top entirely off. I find that my mash-lauter tun is very heavy with 35 lb of wet grain in it, and the handles would make it a lot easier to transport.

If any readers are contemplating building a three-tier system and using Manning's kettle modification, some new dimensions to the brewing stand must be used. My kettles stand 18 in. from the base to the rim; a keg with handles stands 23 in. It would be necessary to raise the middle stand 5 in. and the top stand 10 in. to accommodate the additional height. The overall height, floor to top of liquor tun, would be 92 in. This could be a problem depending upon the ceiling height of the brewing room. If you used the Manning modification only for the mash-lauter tun, you would only need to raise the top stand 5 in., leaving a total height of 82 in.

These are just some considerations that need to be thought out when designing your own system.

-Bob Caplan
Rohnert Park, California

More on Recipe Formulation Calculations

The article "Recipe Formulation Calculations for Brewers" by Martin Manning (January/February 1994) was worth the price of my whole years' subscription! Being relatively new to brewing (one year), I have been struggling to bring all the various parts of brewing together into a united whole. Until I read this article, I was trying to work it out by trial and error with varying degrees of success. I have twice used Manning's calculation method and worksheet with very good results. Not only have my original gravities been within a degree or two of target, but my runoffs have been within a quart of calculated volumes.

And for everything gained, something must be given up. Because the water-to-grist ratio for mashing-in changes for different O.G. targets, I needed to change my procedure for adding my grist to preheated water. I now mash-in with cold water and heat to strike temperature on my burner (single-step infusion). But serendipity has added something even here.

Due to tenderness in my wrists and elbows, I had to motorize my grain grinding, resulting in a higher level of flour in my grist. I start my mash by carefully hand-kneading a small amount of cold water (1/2-1 gal) into my grist. Some sort of enzymatic or chemical action occurs at this point because the mash becomes noticeably warm. Using this technique I have eliminated dry flour pockets from my mash. I have also added a sort of running acid rest by slowing my 85 to 122 °F heating rate to 10-min. These procedures have resulted in two advantages: my sparge efficiency has noticeably improved, and my beers have improved, taking on what I can only describe as a "smooth roundness" or "mellowness." This seems to be independent of maltiness or hops.

The only drawback I've found with Manning's procedure is in the "Calculations of Extract Efficiency." I find measuring "Net Volume of Runoff" to within one cup to be impractical. I am leery of handling hot runoff because of the risk of oxidation and am unable to mark my brew kettle to that degree of accuracy. Instead I make an estimate of efficiency based on O.G. to the volume in my carboy, which is accurately marked. If my O.G.-to-volume is close to target values, then I know my assumed efficiency must be pretty close.

Thanks for the great article. Keep up the good work.

-Steven Kimple
Salem, Oregon

Manning responds: You can base your extract efficiency calculation on the cooled wort volume and its specific gravity, and many people do. However, I have two reasons for preferring to use measurements taken at the start of the boil. First, at that point you have an opportunity to make adjustments to both the boil time and hop rate such that your desired O.G. and estimated IBUs are closely matched. If you wait until the end, you will only be able to correct (by dilution) either the O.G. or the estimated bitterness, and then only in a downward direction. Second, it is the efficiency of the mashing and lautering process that one is trying to calculate and, subsequently, predict in future runs. Factors such as loss of extract to hot trub and spent hops, as well as extract added as kettle adjuncts, will only complicate the problem.

I doubt that I can measure volumes in my kettle to one cup accuracy. I quoted that figure, and the equivalent (for 1.050 wort) 0.0005 S.G. error, as requirements for determining extract efficiency to within 1%. If your kettle is cylindrical and flat-bottomed, a depth measurement using a ruler is a good way to get an accurate volume. You can then multiply the depth measurement by the cross-sectional area (volume per unit depth) to get the volume. To measure volumes in my converted half-barrel, I measure from the rim of the opening to the surface of the wort, then refer to a correlation curve to get the volume. The curve was constructed by first measuring the volume of water required to fill the domed bottom, and the associated distance from the rim. From there on up, the vessel is assumed to be cylindrical, using an appropriate mean diameter.

-Martin Manning
Cincinnati, Ohio

Issue 2.3 Table Of Contents
[Home]  [BrewingTechniques Library]  [Contact Us]  [Order]