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Starting this as a general discussion on mash PH for the more experienced brewers to help out the newbies (Like me) to understand the finer points of checking and adjusting mash PH to improve their beers.

So to start off.

I have bought one of the cheap yellow PH meters off trademe to start checking my mash PH an improve my process. I brewed a simple SMaSH brew today with Gladfields Pilsner malt.

I tested the mash at mash temp (67 degrees C) and had a result of 5.5. I then cooled a sample to room temp (about 23 degrees) and the meter said 6.1. This is a massive difference in PH and 6.1 is a long way from ideal.

My meter does not come with Automatic temperature correction (ATC) so what was my actual mash PH?

And what do I need to do to get an accurate reading of mash PH?I really want to get this right before I start adjusting my mash PH

All help appreciated.

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Have you calibrated the meter with ph solutions?

Yes, the meter was calibrated to a buffer solution at 6.0 PH at room temp




The links I posted are to a website with a great overview of the importance of pH in beer. I find with Wellington water, with pale beers the mash pH starts off at a pH of 6 and needs to be acidified. The pH at mash temperature should be about 0.35 pH units lower than at room temperature. Make sure to calibrate the pH meter with a buffer solution of ph 4 and 7. Mash pH is very important and everyone who is serious about brewing good beer should buy a pH meter IMO. 

Gladfields is well known for having a mash pH about .3 higher than normal which will account for some of it. You can adjust it down with acidulated malt at the rate of 1% of your grain bill for every point you want to drop. So 3% will knock your pH down by approx 0.3.

It may also depend on your water - adding calcium chloride can help with acidifying the mash and bringing your pH down but you should probably do it as part of a wider effort to understand your local water.

My experience with pH meters has made me not trust the cheap ones - there's a recent thread here from someone from Chch who sounds as though they are pretty clued up about pH, meters etc. Maybe track him down and get an accurate baseline on your mash.

Thanks for those links Alex, I have read them, an will re-read them a few times for all that to sink in.

So what is clear now is that I need to test PH at room temp(20 - 25 Degrees) and achieve between 5.2 - 5.8 which leaves me at 6.1 so I need to drop my PH by at least 0.3

The first step in correcting my PH should be getting the water chemistry right. I live in Christchurch and our water chemistry looks like this:



pH after aeration


Acidity to pH 8.3 (as CO3)

1 g/m³

Total alkalinity to pH 4.5 as HCO3

52 g/m³

Turbidity (NTU)

Less than 1

Nitrate Nitrogen

1 g/m³


5.0 g/m³


5.0 g/m³


12.0 g/m³


Less than 0.1 g/m³


1.5 g/m³


1 g/m³


6.1 g/m³

Reactive silica (as SO2)

16.0 g/m³

Total hardness (as CaCO3)

45 g/m³

Conductivity at 20?C (mS/m)


So I should add Calcium Sulphate and Calcium Chloride to about:

80mg/l Calcium

80mg/l Sulphate

70mg/l Chloride

does that sound about right for a reasonably hoppy light beer?

Then if I use 3-4% Acid malt in my mash I should be in the ballpark.

John Palmer also has some good information on mash pH.  Check this link: http://www.howtobrew.com/section3/chapter15-3.html

Right at the bottom of the page there is a great excel spreadsheet to help you calculate required adjustments.  Enter your water profile at the top, then your grain bill and it will calculate an approx mash pH.  You can then adjust the quantities of calcium sulfate, magnesium sulfate and calcium chloride.  A chloride/sulfate ratio above 1.3 can increase maltiness, between 0.77-1.3 is balanced and below 0.77 can increase bitterness.

I have recently brewed my first BIAB brew and took a sample at the end of the mash. Let it cool and then measured the pH with one of the cheap yellow pH meters (calibrated buffer powder of pH 4).

The pH measured 6.3 which seems high compared to what I have read I should be aiming for (5.3-5.8 pH).

A couple of questions:

Should I be taking a sample at the start of mash when grains are added or at the end like I did (60min mash)?

The mash used Auckland Water (Onehunga) with a pH of 7.7 with no other additions. Mash temp was 66degC. OG was 1.050. Grains were: 

Golden Promise (g): 3120
Gladfield Toffee (g): 230

Will this high mash pH ruin the brew, its currently in the fermenter and smells awesome?

Any ideas as to what I can do next time to get closer to the correct pH without adding acids to the water?

Thanks in advance

you could try thickening the mash and sparging if you are currently doing full volume mashes. I mash at 3l water per kg of malt.

Should help increase body too.

Thanks Harry, Yup was a full volume mash. Want to try and keep it simple, hence no sparge. I will try another full volume mash, and if the pH is still high next time will maybe try adding a sparge and reducing the mash volume. Cheers

From memory you need to wait at least 10-15 minutes into the mash for the pH to stabilise before taking a measurement - end of mash is probably fine although too late if you're wanting to do something about it.

Try and find a water report for your area and plug into a calculation sheet - this one is good: http://www.ezwatercalculator.com/ mg/L is pretty closet to ppm so you can transfer them straight over.

6.3 is quite high as you say - it's unlikely that it'll 'ruin' your beer but if you want sharp clean flavours in hoppy beers you really want to get down to the lower end. It's a bit of effort to figure out your water calculations but once you've figured them out you can use them for every brew (unless you switch between light hoppy beers and darker ones - then you might want to figure out some different profiles).

Perhaps start out by adding 200g of acidulated malt to your next grain order and see how you go? Salt additions can also make a big difference to more than just the pH - again once you've figured them out you can use them over and over.

Cheers Sam,  Have just thrown the 'Onehunga, Auckland' water numbers into the EZwater and it looks like my pH should be a lot lower (5.78). I could only find a water report from 2012 so a little bit old.

Starting Water (ppm):
Ca: 8.26
Mg: 7.82
Na: 20.2
Cl: 20.5
SO4: 12.9
CaCO3: 58.3
Mash / Sparge Vol (Ll): 20 / 0
RO or distilled %: 0% / 0%
Total Grain (kg): 3.4
Adjustments (grams) Mash / Boil Kettle:
CaSO4: 0 / 0
CaCl2: 0 / 0
MgSO4: 0 / 0
NaHCO3: 0 / 0
CaCO3: 0 / 0
Lactic Acid (ml): 0
Sauermalz (oz): 0
Mash Water / Total water (ppm):
Ca: 8 / 8
Mg: 8 / 8
Na: 20 / 20
Cl: 21 / 21
SO4: 13 / 13
Cl to SO4 Ratio: 1.59 / 1.59
Alkalinity (CaCO3): 58
RA: 48
Estimated pH: 5.78
(room temp)

I will have another go in the next week or so and take a reading after 10-15 minutes and see how that goes. My next step will be adding 2-3% acidmalt to the grain bill! My water looks very soft so could benefit from some Gypsom or Calcium Chloride to get it into the 'Pale Ale' water profile.

No worries, yeah you can get some variation depending on the time of year and where your water comes from. Your CaCO3 is quite high so I wouldn't be surprised if you need a fair amount of acid malt - maybe right out to 5% (have a play with the spread sheet).

I'd be tempted to just give it a punt unless you're doing dark malty beers a little too low wouldn't hurt - I generally target 5.3 (calculated not measured).


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