Always Question Your Instruments, Brewing Water Tweaks and Fermentation Questions

I am about to brew my first all-grain batch of beer with reverse osmosis (RO) water. I used the EZ Water Calculator spreadsheet to determine mineral additions to the water. Since I am using RO water, I entered in zeros for all of the starting mineral contents. After entering in the grain bill and total water required for the brew day, it determines the amount of salts to add to the water. This, of course, is based on how the grains affect the pH of the mash as well as salts added, with the goal of predicting a mash pH in the range of 5.4–5.6. However, the calculator does not recommend adding any calcium carbonate or sodium bicarbonate to the mash or sparge water. So, here’s my question: Isn’t it recommended to add some alkalinity to the water in order to buffer against pH changes that fall below the optimum? Or is it really dependent on the grain bill, the grist ratio, and the salts added to the strike and sparge water? Here’s the grain bill:

6 lbs. (2.7 kg) pale ale malt
2.25 lbs. (1 kg) Munich malt (10 °L)
0.5 lb. (227 g) caramel malt (60 °L)
0.25 lb. (113 g) Carapils® malt
0.25 lb. (113 g) chocolate malt
0.38 lb. (172 g) white wheat malt

Robb Van Putte
Staunton, Illinois

Grain bill, grist ratio (mash thickness), and salt additions all affect mash pH. I am not going to address specific how-to details related to the EZ Water Calculator in this answer, but after playing around with this spreadsheet I can verify that the tool does not “suggest” salt additions to balance the pH; you need to enter values and use an iterative process to dial in the salts to hit your target before you brew. It’s important to understand all calculations in a spreadsheet that someone else wrote and EZ Water looks pretty solid, but I would like to know more about how mash pH is being modeled, but that’s a discussion for another day.

The higher acidity levels found in darker caramel and roasted grains may require some brewers to add a buffer like carbonates if they are using reverse osmosis or soft water.

The topic of residual alkalinity (RA) is really at the heart of your question and I will attempt to address RA without the use of much math. The term RA is used by brewers to predict whether brewing water will increase or decrease mash pH above a baseline mash using distilled or RO water. Malt labs around the world use standard lab methods to analyze malt and most of the tests run on malt begin by mashing a malt sample in distilled water. pH is one of the values reported on a standard malt analysis and is usually between about 5.7 to 6.0 for base malts (note that so-called congress mashes are very dilute, 8:1 water-to-grist ratio [3.85 qts. per pound], compared to brewing mashes). Brewing waters with negative RA values will lower the mash pH below lab values and waters with positive RA values increase mash pH above lab values.

Carbonates contribute alkalinity to water while calcium and magnesium ions in water react with malt phosphates to release hydrogen ions. Water has a positive RA when the alkalizing effects of carbonates are greater than the mash acidifying effects of calcium and magnesium. I am not going to get into the weeds of RA calculations because all concentrations are expressed as calcium carbonate equivalents (or calcium oxide equivalents if working with German hardness (˚dh) units) and that is a funky, confusing, and deep topic unto itself, but here is the formula for RA:

Residual Alkalinity (as ppm CaCO3 ) = [Total Alkalinity] – {([Ca+2] ÷ 3.5) + ([Mg+2] ÷ 7)}

Note: [x] denotes concentration expressed as CaCO3 equivalents

The divisors (3.5 and 7) associated with the calcium and magnesium concentrations relate to the solubility and acidifying power of calcium phosphate and magnesium phosphate. The bottom line is that RA is used to describe brewing water and how it relates to mash pH.

Most beer in the world loosely falls into the Pilsner style with malt bills almost entirely made up of pale base malt. In the world of specialty beer, recipes, like yours, are much more diverse and often include higher kilned base malts, like pale ale malt, crystal malts, and roasted grains, all of which are more acidic than pale base malts. What this means to the practical brewer is that Pilsner-type brews almost always require some sort of acid addition, such as acidulated malt, lactic acid, phosphoric acid, or calcium additions to move mash pH into the desired range. Pale ales, amber ales, and brews with just a touch of roasted malts often require little to no acid additions because the special malts used for these brews have sufficient acid to bring the pH into the right zone. And when it comes to darker brews, such as dunkel, porter, and stout, carbonate additions may be required if water does not have enough residual alkalinity to offset the acidic, roasted malts used for these styles. And this is what you have asked about in your question.

Here are a few pointers about the latest version, EZ Water 3.02, that may help you out. This calculator does have a place to adjust the pH up by adding slaked lime, baking soda (my preferred salt for this purpose), or chalk. For your recipe, I started with RO water, entered your grain bill (I used the pH data for Vienna malt for pale ale malt considering similar toast levels), assumed 12 L of water for mashing and 12 L for sparging, then added 3 grams of calcium sulfate and 3 grams of calcium chloride. This combination gave me a mash pH of 5.41, which is right in the sweet spot for mash pH.

To switch things up a bit, I increased the roasted malt to a pound (0.45 kg), bumped the crystal malt up to a pound (0.45 kg) and took out the wheat malt. When these changes are made, the predicted mash pH drops to pH 5.3. This is an example where adding alkalinity is needed to buffer the mash pH up. Step 4b in EZ Water is where you can add in alkalinity, and 2 grams of baking soda added in cell E44 gets the pH back up to 5.41. I hope this answer helps to clarify the oftentimes murky topic of brewing water!

I made a yeast starter two days before using 1.5 l of water and 151 g of dried malt extract (DME) (about 3 pints water to 3⁄4 cup DME). After cooling the starter wort and adding the yeast (WYEAST 1098), I put it on a stir plate for 18 hours and then into the fridge. I brought it up to room temperature on brew day, decanted the liquid and pitched.

The recipe said to ferment at 68 °F (20 °C), so that’s what I set my Inkbird/Fermwrap to. Within minutes, the temperature shot up to 85 °F (29 °C). I know that temperature rises during fermentation, but is this rapid increase normal and/or a sign of healthy yeast?

Tom Winiecki
Boulder, Colorado

My column usually lacks a theme within a single issue and my answers tend to be long, but this short answer is going to contribute to a theme in this issue about trust, as in don’t blindly trust what your instruments are telling you.

To recap your question, your measured wort temperature quickly jumped to 85 °F (29 °C) after fermenter filling and yeast pitching, and you want to know if this makes sense. The healthiest and hungriest yeast pitches are simply incapable of very quickly increasing wort/beer temperature from 68 °F to 85 °F (20 °C to 29 °C). There is a way to estimate the heat of fermentation using ASHRAE (The American Society of Heating, Refrigerating, and Air-Conditioning Engineers) data and if anyone out there wants to send in a question about this, ask! But for now, I am going to bunny hop over this rabbit hole. Perhaps the blended temperature of your wort was around 85 °F (29 °C) and you did not discover this until your Inkbird was turned on.

I tend to be a skeptic about observations that don’t seem to make sense.

When an observation seems to be impossible, for example when a pot of water is put on the stove and the measured temperature jumps from 70 °F to 170 °F (21 °C to 77 °C) in a matter of minutes, the likely cause is a measurement error, such as a temperature probe in contact with the vessel surface or a wonky thermometer, instead of an incredible heating rate. A healthy mistrust of instrumentation readings is a quick way of resolving the improbable.

There are numerous scenarios that could explain what happened to this brew, but running through a list of what-ifs is probably not going to help you much in the future. I am a pipe toucher when it comes to process walks in breweries and food processing plant . . . I quickly touch pipes, tank tops, and vent stacks to get a sense of what is happening. This is no joke. A hand tapped on a surface is very revealing about what is happening in the thing being touched. I think I learned this from watching my dad touch the window of the car on road trips before the advent of the modern automobile cockpit. Back in the old days, a finger on the window was a pretty good indicator of ambient temperature. The 20th century human also used this crude temperature measuring method to estimate the temperature of bottles and cans of beer. Since beer bottles/cans in a cooler of ice are often cold on the surface, but warm in the middle, some folks resorted to shaking cans/bottles to equilibrate the sample for a better reading; this of course lead to the awesome drinking game called Beer Hunter.

I’ve noticed over the years that, for some time after my beer hits its terminal gravity, it continues to bubble away and generate foam. It’s not an occasional thing. I’m pretty sure it happens every time, or at least most of the time.

In my simplistic understanding of fermentation, yeast attacks the available sugars and turns them into alcohol and carbon dioxide. So why do I continue to see so much CO2 production after the yeast has ceased producing alcohol?

Gordon Maxwell
London, Ontario

If fermentation is truly complete, what you are seeing in your airlock is most likely the signs of carbon dioxide in the beer equilibrating with the environmental conditions of temperature and pressure. While it may seem that freshly fermented beer should already be in equilibrium with the environment, it’s probably not because carbon dioxide is constantly produced during fermentation and leaves beer in a super-saturated state. The airlock activity is a visual indicator of gas leaving the beer. But this should not be producing foam because the movement of gas out of the beer into the environment is slow.

I tend to be a skeptic about observations that don’t seem to make sense. In this case, you are seeing foaming at the surface of your beer after fermentation is complete. If this was caused by degassing, one would expect beer in a glass to continually foam after a glass is filled. This does indeed occur for some time, but not for long because the rate of de-gassing slows as the carbon dioxide concentration in the glass drops. Beer in an atmospheric fermenter has much less dissolved gas than beer in a bottle, so it’s reasonable to conclude that the foam you see is probably not from simple de-gassing if the foaming persists for hours or days after terminal. Seems to me that the beer is still fermenting.

Hydrometers are great tools, but one of the limitations of their use, especially at home where beer volume is limited, is that relatively few data points are taken to track the course of fermentation. If your observation was limited to a few batches, I would suggest that you may not have enough data towards the end of fermentation to be confident that you have actually hit terminal gravity. For others reading this answer, however, I am suggesting that many brewers declare that terminal gravity has been reached before it actually has based on a couple of data points, or no data points and other metrics like fermentation duration and/or airlock activity. For the sake of discussion, I will assume that the hydrometer reading is relatively constant for a couple of days, but visual cues indicate otherwise.

The proper method for using hydrometers in beer begins with degassing the sample. An easy way to do this is to pull a sample that is a bit greater than the volume of the hydrometer tube, put the sample in a large container (a beer pitcher works great for this), and aggressively pour the sample into a second, clean, dry pitcher (don’t want to dilute the sample with water). This rough pouring process is repeated for another 9 pours. The idea is that 10 aggressive pours between pitchers results in flat beer that is equilibrated with the environment, and therefore cannot degas when a hydrometer is dropped into the sample.

I am going to assume that your samples have not been de-gassed before measuring. Carbon dioxide bubbles escaping from a sample can adhere to the surface of hydrometers and buoy the hydrometer in the sample, resulting in a measurement error that is greater than the actual sample density. Hmmm, this problem would actually make a fully attenuated beer appear to be fermenting as the gas levels drop over time and the buoying effect of carbon dioxide bubbles ceases to cause this error. That’s the opposite of what you are seeing!

Another explanation is that your samples are at different temperatures and you are not accounting for the change in temperature. Liquid density increases as temperature decreases towards its maximum density. Hydrometers with built-in thermometers make it very handy to measure density and temperature at the same time, and then correct the density measurement if the sample is at a different temperature from the hydrometer’s calibration temperature. Since this is normally the case, this style of hydrometer is very convenient.

The information above may or may not give some ideas that help you with your conundrum. The takeaway point is that questioning the basics is a key part of troubleshooting. When the basic indicators disagree, the problem is usually with one of the indicators. Instruments are invaluable tools, but they have a way of spawning red herrings!

I received this phone call a little over a year ago from a colleague. This sticks in my mind as a perfect example of a technical problem that is presented with just enough bias to lure the most suspicious fish:

I just had a question from a customer about a major problem with a whiskey fermentation. The mash was made of 45% distillers malt and 55% flaked corn, which the distiller boiled just to be sure the starch was gelatinized, the mash thickness was 3.2:1, and the mash was held at 152 °F (67 °C) for 90 minutes before cooling to 80 °F (27 °C) into the fermenter when yeast was pitched. The problem is that the fermentation seems to be over, but the final gravity is way high. The distiller is pretty sure the malt was low in enzymes. Any other ideas?

On the surface, this question looks like a no-brainer. Of course the enzymes in the mash were deficient, right? 55% enzyme-free adjunct, longer than normal mash at a moderate temperature perfect for producing highly fermentable wort. And the distiller even cooked the flaked corn just to be sure that the corn starch was gelatinized before bringing down to mash temperature and adding the malt.

The first part of this discussion began by talking about the malt. Distillers malt with a diastatic power (DP) of 260 and alpha amylase level (DU or dextrinizing units) of 60 was used for this mash. Was the adjunct ratio too high? At 55% adjunct, the blended DP was 117 and the blended DU was 27. A value of 60 is the lowest DP that brewers consider manageable and DU should be at around 30 at the minimum. Distillers will reach for exogenous enzymes when the mash is below these general guidelines. So no major concern with the DP in this mash, which is a measure of both the beta and alpha amylase activity. But the DU level, at 27, is a touch low. Too little alpha activity can limit starch breakdown during mashing. One viable suggestion for this and future mashes is to add some fungal alpha amylase to boost the alpha from the malt. But what did distillers do before this was an option? Hmmm, let’s keep that idea in the parking lot for the time being.

Here’s another legitimate question: Are the DP and DU values from malt specifications or from malt “COAs” (certificates of analysis)? The difference between the two designations is that a malt specification defines the typical analytical values for a malt type produced by a given maltster, whereas a malt COA is the actual laboratory data associated with a specific lot of malt. This is like guessing your kid’s height and weight based on your family’s history versus actually measuring your kid’s height and weight once they’re fully grown. In this case, we were looking at a malt COA. Furthermore, when the COA for this particular lot of malt was compared to previous lots of the same type, the lab values were similar. Probably not a problem with the values.

A healthy mistrust of instrumentation readings is a quick way of resolving the improbable.

Onto another usual suspect in fermentation issues, the yeast. Always a great question and in this case the distiller actually performed a forced fermentation to confirm that the final gravity was really it for this fermentation. Although not too common at home, forced/accelerated fermentations are easy to perform by simply over-pitching a wort or beer sample and fermenting the sample on a stir plate. The purpose of the method is to identify the final gravity ahead of the brew being fermented so that there is no guessing about the end of fermentation. In this case, what appeared to be the FG was indeed the FG.

Our advice ended up being pretty simple; drop an amyloglucosidase depth charge into this batch and move on. After all, this was a distiller’s wash and any differences between this spirit and others could be later blended. But the lingering question about what actually happened remained. Being the skeptic, I suggested delicately asking the distiller to consider shining a flashlight on the measured temperature. Blaming instruments can come across as pretty desperate, but sometimes the elephant in the room must be addressed. My colleague explained that this was a new operation with very high-zoot equipment that cost a small fortune. New, expensive pieces of kit normally are pretty trustworthy when it comes to instruments, so probably not the problem. With not having much more to add, it was time to move on to other business.

About two months pass and my phone rings while cruising around in Chicago while searching for a parking spot, and it’s the same colleague who brainstormed with me about the high FG wash. “Hey, Ashton, this is going to put a smile on your face. Remember the distiller? Well, his thermometer was way off and his 152 °F (67 °C) mash was more like 165 °F (74 °C)!” The primary moral of the story is to always question instruments. Always. And the secondary moral is to beware of bias introduced from questions. In this case, the distiller gave us his assessment along with the problem; sometimes the original assessment is the only thing considered and the problem is never solved.

Issue: May-June 2020