This is an article of mine that appeared on HBT 8-12-2015. I thought I would also post it in this, the all-grain & partial mash brewing forum.
Why is my efficiency so low? Can someone explain my efficiency? I thought i understood efficiency. These statements are just some examples of the many threads relating to efficiency that I have seen on Homebrewtalk. It would seem the forum is replete with individuals scratching their noodles in an effort to solve a conundrum their brewing data has presented. Fortunately, there are many helpful members who are ready, willing, and able to crunch the numbers, point out possible errors, and in many instances solve the riddle.
The purpose of this article is not to explore brewing-science's formulae and mathematics, but to illustrate some simple steps involved in the collection and interpretation of useful brewing data. Many homebrewers, myself included, use brewing software to crunch the numbers and calculate efficiencies. Through accurate data collection and analysis, brewers can more easily localize problems with their equipment or methods and find effective solutions. Lets look at two important numbers, mash efficiency and brewhouse efficiency, and explore what each of them means.
Maximum Potential Gravity
Every grain has a variety of descriptive numbers associated with it. One of these is its potential gravity and is measured in points per pound per gallon (PPG). This is the theoretical specific gravity of a gallon of wort containing 100% of the potential sugars in one pound of the grain. A grain-bill’s potential gravity is the sum of the gravity points available from each grain-type. Unless you perform your own grain analysis, this number is dependent on the accuracy of two things; the malsters’ grain data and weight of the grain-bill. Accurately weighing each grain-type is therefore very important.
Specific Gravity
A representative sample of the sweet-wort is taken from the kettle, cooled to the calibration temperature of the measuring device and its specific-gravity measured. Hydrometers or refractometers can be used. I favor narrow-range hydrometers for their ease of use. Both the sample and hydrometer are cooled prior to taking a reading. If only the sample is cooled, adding a room-temperature hydrometer will induce a temperature change and small measurement error.
Volume
The volume of sweet-wort prior to the boil can be measured in a variety of ways. A calibrated dowel, ruler or sight-glass are popular methods. Another approach is to etch volume-markings directly onto the kettle. This is the method I chose. Owing to the high temperatures (~170°F) of the sweet-wort, pre-boil measurements must be corrected to account for volumetric shrinkage to the hydrometer’s calibration point. This correction, approximately a 2.5% reduction in volume from pre-boil temperatures is not automatically made by the popular brewing software I use.
Why is it important to measure mash efficiency?
Multiple enzyme mediated chemical reactions occur in a mash. These reactions produce the fermentable sugars and other compounds responsible for giving a beer its signature characteristics. Knowing how good a job we did at mashing (getting the sugars into our boil-kettle), can highlight procedural problems before and during the mash. Factors negatively impacting the efficacy and efficiency of a mash include:
After mashing and lautering, the wort is heated and boiling ensues with or without corrective measures. If mash efficiency is not in-line with the brewer’s objective, such corrections can include an addition of malt extract or an adjustment to the planned boil duration. This is a completely different, albeit related topic, beyond the scope of this article. When the boil is complete, the wort is cooled and transferred to the fermentor. Brewhouse efficiency can now be calculated.
Maximum Potential Gravity
This is the same measurement as previously calculated. It is based on the malsters’ data and accurate weighings of the various grain-types
Original Gravity
After the boil a representative sample of the wort is taken from the kettle or the fermentor. The sample is prepared in the same manner as before, allowing accurate measurement of the original gravity.
Volume
The volume of wort transferred to the fermentor is easily measured using calibrated markings on the fermentor. I ferment my beer in glass carboys and added etched volume-markings to them. Accurate markings eliminate any guesswork.
Why is it important to measure brewhouse efficiency?
Monitoring and maintaining a high brewhouse efficiency is extremely important for commercial breweries as it significantly impacts their overhead costs and bottom line. Efficiency related cost savings are minimal on the homebrewing scale. I would argue however, that there are important, non-cost-related benefits to developing more efficient brewing practices.
Knowing how good a job was done at getting the sugars into our fermentor enables the brewer to more accurately formulate recipes and water volume requirements at each stage of the brewing process. Assuming mash efficiency is known, the value can also highlight volume losses after the mash and areas where one’s methods could be improved. Factors negatively impacting brewhouse efficiency include:
With accurate data collection, and carefully directed refinement of the approach one takes to brewing, a greater understanding and control of its fundamental processes can be gleaned. Improved control of the home-brewery will inevitably lead to increased efficiency and a welcome additional byproduct; consistency. This is all-too-often overlooked when discussing efficiency numbers.
Unlike the astronauts in “The Simpsons” you don’t need to be "a mathematician, a different kind of mathematician [or] a statistician", but you do need to take accurate measurements. Consistent and predictable efficiency better allows us to craft beers with intended characteristics, not ones dictated by inaccuracies inherent in our home-brewery. Isn't that a worthy goal?
*Certain hydrometers are calibrated to read at the top of the meniscus. Verifying the calibration on your own device is warranted.
The Efficient Brewer
Why is my efficiency so low? Can someone explain my efficiency? I thought i understood efficiency. These statements are just some examples of the many threads relating to efficiency that I have seen on Homebrewtalk. It would seem the forum is replete with individuals scratching their noodles in an effort to solve a conundrum their brewing data has presented. Fortunately, there are many helpful members who are ready, willing, and able to crunch the numbers, point out possible errors, and in many instances solve the riddle.
The purpose of this article is not to explore brewing-science's formulae and mathematics, but to illustrate some simple steps involved in the collection and interpretation of useful brewing data. Many homebrewers, myself included, use brewing software to crunch the numbers and calculate efficiencies. Through accurate data collection and analysis, brewers can more easily localize problems with their equipment or methods and find effective solutions. Lets look at two important numbers, mash efficiency and brewhouse efficiency, and explore what each of them means.
Mash Efficiency
This is a measure of how effective your methods are at extracting the starches from the grains, converting those starches to sugars, and getting the resultant sugars out of the mash-tun and into your boil-kettle. In other words, how effective are you at getting the available sugars into your kettle. It’s no more complicated than that. To calculate mash efficiency we need to know three things.- The estimated maximum potential gravity points in the grain-bill.
- The specific-gravity of the sweet-wort
- The pre-boil volume of sweet-wort in the boil-kettle
Maximum Potential Gravity
Every grain has a variety of descriptive numbers associated with it. One of these is its potential gravity and is measured in points per pound per gallon (PPG). This is the theoretical specific gravity of a gallon of wort containing 100% of the potential sugars in one pound of the grain. A grain-bill’s potential gravity is the sum of the gravity points available from each grain-type. Unless you perform your own grain analysis, this number is dependent on the accuracy of two things; the malsters’ grain data and weight of the grain-bill. Accurately weighing each grain-type is therefore very important.
Specific Gravity
A representative sample of the sweet-wort is taken from the kettle, cooled to the calibration temperature of the measuring device and its specific-gravity measured. Hydrometers or refractometers can be used. I favor narrow-range hydrometers for their ease of use. Both the sample and hydrometer are cooled prior to taking a reading. If only the sample is cooled, adding a room-temperature hydrometer will induce a temperature change and small measurement error.
Volume
The volume of sweet-wort prior to the boil can be measured in a variety of ways. A calibrated dowel, ruler or sight-glass are popular methods. Another approach is to etch volume-markings directly onto the kettle. This is the method I chose. Owing to the high temperatures (~170°F) of the sweet-wort, pre-boil measurements must be corrected to account for volumetric shrinkage to the hydrometer’s calibration point. This correction, approximately a 2.5% reduction in volume from pre-boil temperatures is not automatically made by the popular brewing software I use.
Why is it important to measure mash efficiency?
Multiple enzyme mediated chemical reactions occur in a mash. These reactions produce the fermentable sugars and other compounds responsible for giving a beer its signature characteristics. Knowing how good a job we did at mashing (getting the sugars into our boil-kettle), can highlight procedural problems before and during the mash. Factors negatively impacting the efficacy and efficiency of a mash include:
- Poorly crushed grain
- An overly thick or gelatinous mash consistency
- Excessively low or high mash temperatures
- A large mash-tun dead-space
- Ineffective sparging methods
- Poor management of mash pH*
After mashing and lautering, the wort is heated and boiling ensues with or without corrective measures. If mash efficiency is not in-line with the brewer’s objective, such corrections can include an addition of malt extract or an adjustment to the planned boil duration. This is a completely different, albeit related topic, beyond the scope of this article. When the boil is complete, the wort is cooled and transferred to the fermentor. Brewhouse efficiency can now be calculated.
Brewhouse Efficiency
This is a measure of how effective your entire brewing process is. What portion of the total potential sugars made it into the fermentor. It can never be greater than your mash efficiency and is affected by volume losses during and after the mash. To calculate brewhouse efficiency we again, need to know three things.- The estimated maximum potential gravity points in the grain-bill.
- The original-gravity of the wort (OG)
- The volume of wort in the fermentor
Maximum Potential Gravity
This is the same measurement as previously calculated. It is based on the malsters’ data and accurate weighings of the various grain-types
Original Gravity
After the boil a representative sample of the wort is taken from the kettle or the fermentor. The sample is prepared in the same manner as before, allowing accurate measurement of the original gravity.
Volume
The volume of wort transferred to the fermentor is easily measured using calibrated markings on the fermentor. I ferment my beer in glass carboys and added etched volume-markings to them. Accurate markings eliminate any guesswork.
Why is it important to measure brewhouse efficiency?
Monitoring and maintaining a high brewhouse efficiency is extremely important for commercial breweries as it significantly impacts their overhead costs and bottom line. Efficiency related cost savings are minimal on the homebrewing scale. I would argue however, that there are important, non-cost-related benefits to developing more efficient brewing practices.
Knowing how good a job was done at getting the sugars into our fermentor enables the brewer to more accurately formulate recipes and water volume requirements at each stage of the brewing process. Assuming mash efficiency is known, the value can also highlight volume losses after the mash and areas where one’s methods could be improved. Factors negatively impacting brewhouse efficiency include:
- Mash efficiency (brewhouse efficiency can never exceed this number)
- Spilled wort
- Dead-space in the kettle, chiller and hoses
- Wort absorbed by hops
- Kettle-trub
With accurate data collection, and carefully directed refinement of the approach one takes to brewing, a greater understanding and control of its fundamental processes can be gleaned. Improved control of the home-brewery will inevitably lead to increased efficiency and a welcome additional byproduct; consistency. This is all-too-often overlooked when discussing efficiency numbers.
Unlike the astronauts in “The Simpsons” you don’t need to be "a mathematician, a different kind of mathematician [or] a statistician", but you do need to take accurate measurements. Consistent and predictable efficiency better allows us to craft beers with intended characteristics, not ones dictated by inaccuracies inherent in our home-brewery. Isn't that a worthy goal?
*Certain hydrometers are calibrated to read at the top of the meniscus. Verifying the calibration on your own device is warranted.
