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Frugal Brewing: Choosing a Thermometer

New brewers will brew better with a good thermometer.

Dave Carpenter Apr 19, 2016 - 5 min read

Frugal Brewing: Choosing a Thermometer Primary Image

Cheap and frugal are very different things. To be cheap is to prioritize cost over all else. Being frugal, however, means not spending more than is necessary while still considering quality, time savings, performance, and other factors. An inexpensive stockpot whose handles fall off after only a couple of brew projects is certainly cheap, but to buy such an item is not frugal. After all, what good is a cheap brew kettle if you have to replace it within a couple of months?

It is this philosophy that leads us to take a look at thermometers. Those who are just starting out in brewing will do just fine with an inexpensive (cheap) thermometer. There are several kinds of thermometer technology from which to choose:

The standard-issue alcohol thermometer that comes with many homebrewing starter kits is familiar, cheap, and generally reliable. However, the alcohol inside the glass may have a low boiling point (depending on the type of alcohol used), which means it could vaporize and condense within the channel if not fully submerged. Repeated cycling of this boil-and-vaporize process can cause bubbles to form in the line of alcohol, rendering the thermometer useless. Also, glass thermometers can break easily.

Kitchen dial thermometers often feature an internal bimetallic coil, which consists of two different metals joined together. Because the two metals expand at different rates when heated, the helix twists proportionally to the temperature. This twisting turns the dial and indicates temperature.

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Thermistor-based thermometers measure temperature by way of an electrical resistor made of a semiconductor. The resistance of the semiconductor changes with temperature, so measuring the resistance allows one to infer the temperature. Thermistors are often very nonlinear, which means that they’re optimized for a fairly narrow range of temperatures, outside of which there might be less accuracy.

A thermocouple-based thermometer uses two wires of constant resistance located in the probe. When heat is applied to these wires, a small electrical current is created, and the temperature is inferred from the difference in voltage between the two wires. Thermocouples are usually fairly linear in their behavior, meaning that they act more or less the same over their entire temperature range.

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Meat thermometers, generally of the bimetallic coil or thermistor variety, are inexpensive and excellent for brewing because they cover a relevant range of temperatures:

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  • Specialty grains should be about the same temperature as medium-well to well-done beef (155°F/68°C).
  • The mash should be somewhere in the medium-well beef to ground pork range (148–160°F/64–71°C).
  • Sparge water shouldn’t get any hotter than ground turkey (170°F/ 77°C).

Beware of some candy thermometers, however. Their temperature range is often much higher and can be unsuitable for brewing.

A cheap thermometer can get you started, but for consistency and accuracy in all-grain brewing, a quality digital thermometer is an excellent investment. Grains mashed at 145°F and 155°F (63°C and 68°C) will produce two very different worts: Even a couple of degrees can make a big difference. The Thermapen digital thermometer by ThermoWorks is a popular choice for brewers who desire accuracy, repeatability, and ease of use.

Among the features of this thermocouple-based thermometer are:

  • Accuracy of ±0.7°F (±0.4°C) in the range of temperatures relevant for brewing.
  • Response time of less than three seconds to within 1°F (0.6°C) of the measured temperature.
  • Easy adjustability to work in both Fahrenheit and Celsius.

A Thermapen will set you back around $100, but its accuracy, response time, and ease of use make it a wise, even frugal, investment. Many homebrewers (myself included) have reported noticeable improvements after switching to a high-quality digital thermometer such as the Thermapen.

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