Today we’re diving into a topic that confuses brewers more than almost anything in water chemistry: alkalinity.

pH VS ALKALINITY

pH and alkalinity are not the same thing. pH is the ratio of acid to alkaline.

Alkalinity is the amount of alkaline that is present. Two completely different things.

Let me make this clearer with a couple of analogies.

CAR AND CARAVAN ANALOGY

Imagine you are towing a caravan.

The car pulling it is acid. The caravan is alkalinity.

If the caravan is light, even a small car can move it.

That is low alkalinity, and a tiny bit of acid shifts the pH easily.

If the caravan is heavy, the car struggles.

That is high alkalinity, and the pH barely moves even with a fair bit of acid.

That is alkalinity, resistance to lowering pH.

MARBLES ANALOGY

Now imagine marbles.

Red marbles are acid. Blue marbles are alkaline.

One red and one blue marble gives you a neutral balance,

I am using pH 7 here simply as a teaching analogy.

But the alkalinity is tiny, add one more red, and the pH shifts dramatically.

Ten red and ten blue, still neutral, but alkalinity is higher,

add one red and the pH only moves a little.

One hundred red and one hundred blue, still neutral, but alkalinity is huge,

add one red marble and the pH barely moves.

pH is the balance. Alkalinity is the amount.

THE THREE DEFINITIONS OF ALKALINITY

Water treatment people use three definitions.

Number one, Alkalinity is the water’s ability to resist a pH change.

Number two, Alkalinity is the water’s ability to neutralise acid,

in other words, how many bases in the water can mop up hydrogen ions.

In brewing, that is almost all bicarbonate.

Number three, Alkalinity is how much acid it takes to push the water down to pH 4.5.

Below that, alkalinity is gone, and pH falls very quickly.

Your water report’s alkalinity number is based on this pH 4.5 test.

pH 4.5 is the standard endpoint for total alkalinity titration.

We will go deeper into that another time.

WHAT ALKALINITY ACTUALLY MEANS FOR BREWERS

Alkalinity is your water’s ability to resist a drop in pH.

It comes from bicarbonate, carbonate, and a tiny bit of dissolved CO₂.

Here is an important detail, in normal drinking water, pH 7 to 9,

over ninety eight percent of the carbonate system is bicarbonate.

So for brewers, alkalinity basically is bicarbonate.

Bicarbonate is the primary buffering system in brewing water.

WHY ALKALINITY MATTERS

High alkalinity raises mash pH, it can make pale beers harsh, dull, or grainy.

Low alkalinity lets mash pH fall easily, great for pale beers,

but it can fall too low in dark beers.

Very low alkalinity, around 0 to 30 ppm, can make beer taste thin or watery.

Moderate to high alkalinity, around 100 to 200 ppm,

helps buffer the acidity of roasted malts in stouts and porters,

and it prevents acrid, burnt flavours.

Pale beers want low alkalinity.

Dark beers want moderate to high alkalinity.

 HOW TO ADJUST ALKALINITY

To lower alkalinity

Use lactic acid or phosphoric acid, acidulated malt,

or dilute with RO or distilled water.

Prefer lactic or phosphoric,

they are predictable, repeatable, and easy to calculate.

Why not rely heavily on acidulated malt?

Because its acidity varies between maltsters,

large amounts can add lactic flavour,

and it makes mash pH correction slow and imprecise.

Dilution

Dilution works well when you do not need a huge correction.

If your alkalinity is 100 ppm and you want around 50,

a simple one to one mix of tap water and RO or distilled water

will get you close.

De- alkalisation by boiling

You can also remove alkalinity by boiling. Bring the water to a rolling boil.

You may add a small sprinkle of chalk to speed things up,

but boiling alone will remove some alkalinity.

Boiling drives off CO₂, and once the CO₂ is gone, 

the water cannot hold as much bicarbonate.

Calcium and bicarbonate will crash out as chalky solids.

Let it cool, let it settle, and pour off the clear water from the top.

Done properly, this usually leaves you with around 60 to 90 ppm alkalinity.

To raise alkalinity

Use baking soda, it is the easiest and most predictable method.

You can use chalk, but it barely dissolves unless the water is carbonated,

so it is difficult to use correctly.

Slaked lime works too, but it is tricky, it's easy to over correct and can be corrosive.

Most brewers should stick to baking soda.

So in summary:

pH is the balance.

Alkalinity is resistance to lowering that balance.

And bicarbonate is the superstar behind it all.

In the next video, we will look at how alkalinity interacts with hardness,

and how Residual Alkalinity, or RA, predicts mash pH even better.

Every brewer seems to know that one guy who  says, 

“Mate, you ONLY need this magic number,” or 

“This ONE mineral is all that matters.” 

 Yeah… nah, not even close. 

 That’s marketing hype mixed with wishful thinking. 

Water chemistry is a team sport, not a solo act, and pH 

is one of the Most Valuable Players. 

From your mash, to the boil, into the fermenter, and all 

the way to that final pint, pH is quietly influencing 

everything, like a backstage manager that never sleeps. 

And sure, you might fluke a good beer without paying 

attention to it, but if you want to dial things in, fix 

problems, and make beer that tastes intentionally good 

instead of accidentally good, pH is your new best mate. 

This is Part 2 of my brewing water series, so if you 

missed Part 1, it’s worth watching. It’ll make some of the 

terms in this video make a lot more sense. And, like 

always, I tuck a bit of bonus science at the end for the 

curious minds who enjoy a nerdy nightcap. If you 

skipped that in Part 1, or haven’t watched it at all, there’s 

a link in the description. 

 Fun Fact - Oxygen means Acid Maker 

Alright, before we start throwing numbers around like 

we’re filing tax returns, it helps to understand why pH 

does what it does and what’s actually going on behind 

the scenes. 

 So let’s kick off with the basics. 

What does pH mean?

pH p=Power H=Hydrogen 

pH stands for the “Potential of Hydrogen” 

 More accurately, the "p" is a mathematical notation that 

stands for the negative logarithm (base 10) of the 

concentration or activity of hydrogen ions ([H⁺]) in a 

solution. Remember at School, yep one of those buttons 

on your calculator Log Sin Cos.  

 You might be used to hearing “acid and alkaline” but 

since we’ll be talking about alkalinity in another video, 

it’s less confusing to use the word "base" or “basic”. So 

you have acids and bases. 

 In simple terms, pH is a scale that tells us how acidic or 

basic water is. It’s based on the concentration of 

hydrogen ions present, acids gain hydrogen ions  and 

create hydronium and bases are created by losing 

hydrogen ions and creating hydroxide but because 

those numbers get incredibly small, we use a logarithmic 

scale to make it easier to work with. 

 A logarithmic scale simply means each 1 step change in 

pH represents a tenfold change in acidity. For example, 

something with a pH of 5 is ten times more acidic than 

something with a pH of 6. 

 If we look at the pH range from 0 to 14, each step is a 

tenfold change, which means the entire range spans a 

factor of 100 trillion. That’s an almost unimaginable 

difference. If pH 0 were represented by a single 1mm 

grain of sand, then pH 14 would be 100 trillion grains, 

enough to fill 40 Olympic swimming pools or build a 

small beach. If pH 0 was 1 second, then pH 14 would be 

over 3 million years. This is why the pH scale uses 

logarithms, to compress a truly enormous range into a 

simple number. 

Why does pH matter in brewing

pH is crucial because it affects almost every stage of brewing: 

1. Mash Efficiency 

Enzymes like amylase convert starches to sugars 

best in a slightly acidic range, around 5.2 to 5.6. 

Outside this range, enzyme activity drops, reducing 

sugar extraction, efficiency and ultimately affecting 

alcohol content. 

2. Flavour Development 

pH affects the taste of the final beer: 

 Lower pH can make beer taste sharp or tart. 

 Higher pH can lead to dull or soapy flavors. 

pH also influences hop utilization, too high or too 

low can reduce bitterness extraction. 

We will dive deep into pH and beer flavours in a 

future video. 

3. Yeast Health & Fermentation 

Yeast prefers a slightly acidic environment. Correct 

pH helps yeast ferment efficiently and reduces the 

risk of off-flavors or stalled fermentation. 

4. Microbial Stability 

A lower pH helps inhibit unwanted bacteria, 

improving the beer’s shelf life and safety. 

5. Clarity & Stability 

pH affects protein precipitation and polyphenol 

interactions, which influence clarity and haze formation. 

How to Measure pH

1. pH Test Paper or Indicator Sticks 

These strips change colour depending on the 

acidity or alkalinity of your solution. You dip the strip 

into your liquid and compare it to a colour chart. 

Each colour corresponds to a different pH. Though I 

am yet to find any with high accuracy. And with dark 

beers that can change the colour of the strip, 

accuracy is near impossible. 

2. pH Meters 

A probe is dipped into the wort or beer, giving a 

precise digital reading. Many, if not all serious 

brewers who care about their beer use pH meters. 

They are used through the whole process from 

mash to fermenter. A detailed test equipment video 

will be later in this series. A quick tip for those 

already using them, calibrate whenever you use 

them and make sure the calibration fluid is at room 

temperature around 20c or  68F and the same with 

the wort sample,  doesn't matter if it has ATC 

Automatic temperature correction or not, to get 

accurate readings it’s what you have to do.  

Tip 

To some people this might sound odd, but in brewing, as 

long as you’re starting with potable water, water that’s 

safe to drink, the actual pH of your tap water isn’t a big 

deal, it doesn’t matter. In most places it falls somewhere 

between 6.5 and 8.5 anyway. Once you add grain, the 

mash naturally contains buffers that pull the pH into a 

range that's easily tweakable when needed, so the 

starting water pH rarely affects anything by itself. 

Buffers, that brings us to Alkalinty, that's for the next 

video and it is hugely important.  

pH tells us the ratio of acid to base, but it doesn’t tell us 

how much total acid or base is in the water. That’s 

where alkalinity comes in.  

 In the next video I’ll show exactly why alkalinity matters, 

and why water with high alkalinity is much harder to shift 

in pH than water with low alkalinity.