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Mark

Homebrewer, eternal E'Lir, Physics, and Math Student.

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Overview

Preliminaries

Before we get started, I have to say something about the importance of having good information. Just like using any calculation, garbage in gives garbage out. If you tell the efficiency calculator that you have 5.5 gallons, but you actually have 5.7 gallons, then all of the calculations have a substantial margin of error. To that end I’m going to annoyingly list a couple methods of accurately measuring your volumes, how to read a hydrometer, and a refractometer.{: .notice}


Volumes

There are three common methods of measuring your volumes; dip sticks, rulers, and kettle etching. Dip sticks are usually a wooden dowels with notches placed every so often to indicate a volume for that particular kettle. A dowel for one kettle will not work for another kettle as the diameters of the kettle, and thus the height of one gallon of water will be different. My main issue with this is that very act of notching the dowel introduces an unnecessary source of error, so I don’t usually suggest going this route. Next up is the dip stick 2.0, also known as the humble ruler. While these are not pre-marked with volume measurements, they’re going to be much more accurate and versatile. Simply measure the interior of the kettle and use a little bit of math, the formula for the volume of a cylinder, to determine the volume of water or wort. Lastly kettle etching, while an interesting and useful project, it suffers from the same drawbacks as the lowly dip stick, low instrumental precision and being specific to the kettle applied. If you do go this route, I would suggest doing it in smaller increments, as measurement error is half the smallest unit of measurement on the instrument. With that said, there’s one more thing to be aware of, and that’s thermal expansion ie. Liquids expand as they’re heated and contract when they’re cooled. This means that anytime you measure the volume, you should also measure the temperature and record both of these values, then calculate the volume when at room temperature using the formula below.*

T = Temperature in Fahrenheit.
V = Volume when measured.
Volume_Chilled = V * ( 1.05606 x 10^-15 x Temp - 7.43014 x 10^-13 x A25 + 2.19998 x 10^-10 x A24 - 3.74236 x 10^-8 x A23 + 5.15858 x 10^-6 x A22 - 2.73712 x 10^-4 x A2 + 1.00452 )

Unless you’re extremely comfortable in your brewing setup, and don’t care about these calculations, then don’t eyeball your volumes.

Specific Gravity

Without a specific gravity reading, this entire post would be pointless. There are currently two tools typically used to measure your specific gravity, the hydrometer, and the refractometer.

Hydrometers

We’ve all used a hydrometer before, but did you know that for most hydrometers you’re supposed to read the gravity from the TOP of the meniscus and not the bottom? Weird I know. Moreover, you should ensure the sample is cooled to the reference temperature indicated at the bottom of the hydrometer. There are temperature adjustment calculations, but they’re not precise and introduce yet another point of error, however if you at least cool to room temp, it should be less than the instrumental error of the hydrometer scale (0.005 for most wide range hydrometers). The exception being short range hydrometers such as fg hydrometers that have higher precision due to the smaller range of readings.

Refractometer

Using your refractometer may seem like a simple process, but there’s a correction factor to account for. The wort correction factor is typically assumed to be 1.040 but will range with different worts, some have attributed relationships between SRM and the wort correction factor. My intuition is that it will instead depend on the sugar composition in the wort, and since dark beers are generally mashed at a higher temp, they have a greater number of long chain sugars and dextrins, so it may correlate better with mash temp or expected fg. The simple approach is to: 1) Calibrate your refractometer and hydrometer to zero using some water. 2) Make up some wort of known gravity using some water and DME. 3) Carefully measure the gravity using both instruments. 4) Divide the hydrometer reading by the refractometer reading, typical correction factors are 1.04 (sucrose based refractometer scales) or 1.00 (pre-calibrated in factory). Another thing to be aware of is the scale used during production of your hydrometer/refractometer, 25 brix should correspond to 1.106 and not 1.100. If it’s 1.100 then they used the old rule of thumb of multiplying by four, and so if this is the case you should always record the gravity reading in brix, and then convert to specific gravity using a tool of your choice. Lastly, you can use a refractometer to measure your final gravity but you have to use an accurate FG correction tool. The best ones at the moment are those based on the findings of Sean Terrill.


Efficiencies

Alright, now that we got the boring parts over with, time to talk about the important things, calculating the effectiveness of your brewing process and system. Now don’t get me wrong, efficiency chasing is not the goal of this article, but rather understanding your system and being able to make a change in order to produce consistent beer. There are multiple kinds of efficiencies, conversion efficiency, lauter efficiency, mash efficiency, kettle efficiency, brew house efficiency, and each one is useful in determining something about your process. Professional brewers have additional types of efficiencies, like casting and packaging efficiency, which accounts for loss of volume due to evaporation during whirl pooling and hop stands. Each efficiency will be explained in the order at which it comes up in your brewday. All calculations were done using a batch sparge simulator created by user Doug293cz over at HBT, that was based on the findings and simulations of braukaiser then adapted for variable grain absorptions, which I then implemented into my calculator at Priceless’ BiabCalc.

Conversion Efficiency

This calculation compares the total amount of extract available from your grains, the potential extract, to the amount of sugar converted from the mash. The measurements needed are the volume and gravity of the first runnings of the mash. For those that aren’t familiar, the first runnings are the sweet liquor (unhopped/unboiled wort) that is drained off from the mash before you lauter or sparge. If you BIAB, this would be the wort released after pulling the grain bag and squeezing or allowing it to drain via suspension. There are techniques and mash parameters that affect conversion efficiency, however the most important technique is a proper dough in. It’s not enough to simply mix together the strike water and grains like you’re making pancakes or muffins. You want that stuff to be completely homogenous, ie no dough balls. STIR THE CRAP OUT OF IT. The mash parameters that affect conversion efficiency are the grain crush, mash times, mash temps, diastic power, mash thickness, mash thickness, and mash pH. None of these variables will necessarily lower the conversion efficiency, but they all affect the speed at which the conversion occurs. By increasing your conversion rate you can increase your conversion efficiency given the same time period, and you can’t always mash longer as there is a point at which mashing longer will produce zero difference as the enzymes denature. Things that slow the conversion are: coarse grain crush, too high or too low of mash temps, low diastic power (low percentage of base malts in the recipe), thick mashes less than 1 qt/lb, thin mashes greater than 3.5 qt/lb and to a lesser extent poor mash ph. What I’ve read is that the mash ph will affect your flavor profile long before it significantly impacts the conversion efficiency. Do everything the opposite of the above to increase your conversion rate; mill finer, manage your mash ph, increase your diastic power or add enzymes, use a thinner mash in the 1.5-2.25 qt/lb range. Typical conversion efficiency is around 95%, with exceptional conversion rates being in the 97-98% range. Understand that each batch of malt will have slightly different grain specifics, and so your calculations are usually in the +-1% from that alone.

Calculating

T = Temperature in Fahrenheit.
V = Volume when measured.
Volume_Chilled = V * ( 1.05606 x 10^-15 x Temp - 7.43014 x 10^-13 x A25 + 2.19998 x 10^-10 x A24 - 3.74236 x 10^-8 x A23 + 5.15858 x 10^-6 x A22 - 2.73712 x 10^-4 x A2 + 1.00452 )

Troubleshooting

Check the crush, then check the crush again. Then look at your mash Ph, check the crush, then look at your water chemistry, and check the crush again. If you still have low conversion efficiency it could mean your grains have a different yield than what is in the computers grain database, you might have issues with your strike temp and accidentally denatured some enzymes by doughing in too hot, you might need to crush finer, or mash longer. If you have a refractometer, take a gravity sample every 5 minutes, when the gravity has stopped increasing, mash another 10 minutes, if it’s still the same then your mash is done and no further conversion is going to take place.

Lauter Efficiency

The next step in the brewday after draining your mash tun is the sparge, or maybe you’re doing no sparge aka full volume mashing? Either way, you still have a lauter efficiency! This is a measure of how effective your sparge is, depending on your technique and equipment it’s usually 70-80%. The required measurements are volume** and gravity of preboil. Losses in mash tun, or high absorption rates will kill this and bring this efficiency down very quickly. A proper batch sparge is just done exactly the same as the initial dough in, take your grains, combine it with some water, and stir the crap out of it. I recommend stirring with a whisk if possible. Let it rest for a few minutes, then stir the crap out of it again, then drain the second runnings. No sparge mash tun brews usually are around 69%, the same setup for BIAB is usually around 72% given the lower grain absorption rate. A batch sparge with a mash thickness around 1.5-1.75 qt/lb and near equal runnings should give about 80-81%* lauter efficiency. The same setup with a BIAB squeeze should increase that to about 86-87%* lauter efficiency. A fly sparge should at the very least increase your lauter efficiency by at least 3%, if you’re not at least matching the above batch sparge lauter efficiencies by fly sparging, you’re mash tun is probably not set up optimally for a proper fly sparge and you’re getting a considerable amount of channeling, my recommendation would be to do a proper batch sparge and see if you get better results.

Calculating

T = Temperature in Fahrenheit.
V = Volume when measured.
Volume_Chilled = V * ( 1.05606 x 10^-15 x Temp - 7.43014 x 10^-13 x A25 + 2.19998 x 10^-10 x A24 - 3.74236 x 10^-8 x A23 + 5.15858 x 10^-6 x A22 - 2.73712 x 10^-4 x A2 + 1.00452 )

Troubleshooting

There’s not much to do for troubleshooting this aspect, if you’re doing it correctly then it’s pretty straight forward. Batch sparge should have lots of stirring, fly sparging should have minimal chandelling and are usually performed slowly.

Predictability vs Consistency

I have been seeing some misleading posts lately regarding consistency in their efficiencies, and so I propose separating these two concepts. A consistent efficiency should only apply to doing the same recipe repeatedly, while a predictable efficiency should be able to take your average efficiency and your process into account and using a simulator like my own to predict what a comparable efficiency would be for this new recipe. Stating that “I always get 76%” is very misleading for new brewers, and doesn’t tell them anything about your setup or process, without providing significantly more information. While getting exactly the same efficiency is great for nailing down a particular recipe, it’s not that useful for those that don’t repeatedly do the same brew. Predictable would instead say “I usually get 76% on an average brew, so for this large grain bill I should instead expect 64%.” Predictability should be the goal for understanding your system.

Summary

You need three accurate measurements for any talk about efficiency; Gravity, Volume, and Temperature. Without gravity, and volume it’s absolutely pointless, while without temperature it’s inaccurate. The reason for temperature is that the calculations usually assume you’re entering chilled volume and so you need to calculate what the temperature would be once cooled.

Useful Measurements on Brewday

To fully understand your system, and to figure out what went wrong, you need at least three sets of data. First runnings gravity and the strike volume gives grain absorption rate, and conversion efficiency. Pre-boil gravity and volume gives total mash efficiency, if you also have the first runnings info then you can calculate the lauter efficiency as well. Post boil gravity and volume gives the boil off rate and mash efficiency.

Mash Efficiency

Mash efficiency, is the combination of conversion and lauter efficiencies. The formula is simply Mash efficiency = conversion efficiency * lauter efficiency. However it’s of little use to anyone trying to troubleshoot or understand their setup despite being the second most commonly mentioned variable and I won’t go on much about it besides its usefulness for scaling recipes.

Calculating Mash Efficiency

T = Temperature in Fahrenheit.
V = Volume when measured.
Volume_Chilled = V * ( 1.05606 x 10^-15 x Temp - 7.43014 x 10^-13 x A25 + 2.19998 x 10^-10 x A24 - 3.74236 x 10^-8 x A23 + 5.15858 x 10^-6 x A22 - 2.73712 x 10^-4 x A2 + 1.00452 )

Brewhouse Efficiency

Similar to Mash efficiency, there’s not much going on here. Any losses after the boil occurs will affect this number. For those with zero kettle losses, brew house efficiency = mash efficiency. While this is usually the reference point when people say “I get xx efficiency”, this is a pretty useless metric in my experience as unless you have significant losses after chilling, it’s not going to help much.

Calculating Mash Efficiency

T = Temperature in Fahrenheit.
V = Volume when measured.
Volume_Chilled = V * ( 1.05606 x 10^-15 x Temp - 7.43014 x 10^-13 x A25 + 2.19998 x 10^-10 x A24 - 3.74236 x 10^-8 x A23 + 5.

Myths, Mashout, and More

The first myth on the agenda is that BIAB gets low mash efficiency. This is just not true. I have never met any brewer that does biab regularly, and has consistently gotten less than 70% mash efficiency. The fact of the matter is that by squeezing the grain bag, they’re increasing their lauter efficiency. All other things held equal, there is no way that this can decrease any other efficiency measurement. Lower absorption rate = higher lauter efficiency.

The second myth is related slightly, thin mashes do not give lower/slower conversion rates. Likewise, enzyme concentration is not a convincing model that can predict conversion rates, otherwise we would all be doing super thick mashes. You need sufficient enzyme concentrations, don’t go over ~3.5 qt/lb mash thickness, and you need good water to grain surface area exposure. This can be done by an inline hydration like in professional breweries, by recirculation, mashing thinner or by a thinner mash. I recommend 1.75-2.25 qt/lb for good conversion efficiency without sacrificing too much lauter efficiency due to the decreased sparge volume and runnings ratio.

This might upset some people but a mashouts a purpose is NOT to increase efficiency, nor is it to change the viscosity and make rinsing the sugars more effective. A mashout denatures the enzymes and locks in the wort composition. This really only applies in my mind for fly sparging, or other slow sparging methods. If you’re doing biab, or doing a 5-15 minute batch sparge then there’s no need to mash out at all. If you’re reporting a efficiency gain from a mashout then the most likely explanation is either due to a second sparge volume or that you’re really extending your mash time and not getting full conversion in the original mash time and you’ll benefit as much or more by mashing longer, or crushing finer.

Lastly, it would be wonderful if everyone could stop saying I get xx efficiency, without saying which efficiency you’re talking about, when discussing their issues with new brewers. As that’s so arbitrary it’s all but useless. Instead discuss your conversion efficiency, lauter efficiency and your process so that they understand!