One for the PH boffins

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The Baron

The Baron

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Right is this correct what I have just found out that the mash PH levels generally required are between 5.2 and 5.5 are at the mash temp so if we cool the PH sample down to room temp the reading we get at 20c needs 3.5 adding to it. The reason I ask is I have just brewed and my cooled PH was 5.8 and its blagging my head if it is near correct or not. Help
 
No I've never experienced that.
pH decreases with an increase in temperature, but the solution doesn't become more acidic.
Test mash pH and use whatever compensation required to give an accurate reading for whatever you are using. What are you using to measure pH?
Lots of probes have ATC and as long as you aren't crazy high/low will handle things for you just fine.
If you are using strips or liquid indicator ... just don't sweat it so much.
Not only are they a only a very broad indicator ( ... looks like a 5 maybe?!) but the bit you use to test might as well have cooled to nothing.
Even when using a probe and a sample in a tube the sample volume is small enough to cool quite quickly.

Your mash pH sample was 5.8? This is a little high. It could have potentially increased quite a lot during the sparge. Was this straight from the mash or during the sparge? I do pre and post boil samples these days because it is enough and ... mash is quite often too late. I know that as long as my pre boil is healthy, my mash will have been fine because the sparge drags it back up. If not, adjust for next time.
 
Hi I use a digital PH meter that has been calibrated and the mash was measured about 15mins in and at the end with the same reading of 5.8. I did not measure after the sparge but do not do a intense sparge kjust a simple kettle sparge of about 10 litres over the grains
 
the baron said:
I have just found out that the mash PH levels generally required are between 5.2 and 5.5 are at the mash temp
Click to expand...
No, the recommended pH range (around 5.2 - 5.7) is for a mash sample taken at room temperature. Yeah 5.8 is a touch high but nothing to be concerned about really.
 
Thanks for that chaps you see so much conflicting info on the net that it can spook you even a well established brewer like myself with years under my belt. I have only just got the PH meter and it is the first time I have used it the good news is that it now reads after the sparge at 5.6 so it looks all good to me Thanks both of you
 
Hi Steve and stz
just to add to this this I found this comment on another forum so this person must have read the same info I had
“Hot wort will almost always provide a higher pH reading than the actual wort”

I’m not sure this is correct. From my understanding, hot wort (ie. wort at mash temps such as 150*) will have a *lower* pH reading than wort at room temps – typically around .35 pH lower. Meaning that if you’re shooting for 5.2 pH at mash temps, you want to really hit 5.55 at room temp. I’ve read wort at higher than typical mash temps (~170*), say for mashout have about a .45 adjustment factor.
Thanks Pete
 
Yeah you're right, at mash temperature the pH will read lower than it would if cooled to room temperature. Braukaiser says that the difference is generally accepted as 0.35 pH units, but from his experimentation reckons it's closer to 0.2 pH.

There seems to some confusion though, the optimum pH (around 5.5) is for a room temperature sample. So if you're testing at mash temperature it'll be something like 5.15 - 5.3.

I'd recommend testing at room temperature, it doesn't take long to cool a small sample in the fridge and it'll be easier on your pH meter.
 
So there is a little truth in it then Steve so my room temp PH was 5.8 so really circa 5.6. Thats good news that I am not that far out then Once again thanks
 
the baron said:
So there is a little truth in it then Steve so my room temp PH was 5.8 so really circa 5.6. Thats good news that I am not that far out then Once again thanks
Click to expand...
No I think you've misunderstood. When we read that the ideal mash pH range is 5.2 - 5.7, that is when measured at room temperature. If you want to measure pH at mash temperature (not recommended) then the ideal range will be about 5.0 - 5.5.
 
Doh let me get this right then Steve so my 5.8 @ room temp is 5.6 @ mash temp so I am 1 degree outside the advised parameters. Please I hope I have got it right this time
 
the baron said:
Doh let me get this right then Steve so my 5.8 @ room temp is 5.6 @ mash temp so I am 1 degree outside the advised parameters. Please I hope I have got it right this time
Click to expand...
That's it. And 0.1 pH isn't worth worrying about. Just take note of it and next time you brew something similar, reduce the alkalinity a little more.

Another thing while we're on the subject, is the confusion around ATC on pH meters. A lot of people erroneously think that ATC means they can test at mash temperature but the meter will display the pH adjusted to its room temperature pH. That's not what it does, I believe it's simply to improve accuracy when testing samples at a different temperature to the calibration temperature, but it'll still show the actual pH at the current temperature. In other words, always test at room temperature :D
 
Thanks Steve. How would you best adjust the PH if I needed to as I use the same water set up each time and do not adjust it. I know you are a expert on this forum re water but I do not have the time to go into it as my beers have always generally been ok but if I wanted just bring it down a couple of points to get it in the sweet spot what would you generally add to a 23ltr batch to do this and how much in my situation.Thanks Pete
 
There isn't really a simple one size fits all approach unfortunately, but since you now have a data point for that particular recipe then it's a simple fix.

The easiest is to replace a little of the base malt with some acid malt. Again according to Braukaiser (he's the real expert, I'm just an imposter who steals the findings of much smarter people :D) each 1% (of the grist as weight) of acid malt reduces the mash pH by approximately 0.1.

So an inclusion of 3% acid malt would give you a mash pH of 5.5. Of course that only applies to that particular recipe, or something similar, crystal or roasted malts will lower pH also, but it's extremely difficult (in practical terms near impossible) to estimate this effect with any accuracy.
 
Thanks Steve I know the PH will vary with the grainbill I just needed a reference point. I have some acid malt so will use that next time after testing the mash PH. It could be the start of me starting to understand water treatment you never know. Thanks for the invaluable advice
 
The standard advice to mash at between 5.2 and 5.6 pH is for samples cooled to 25 degrees C. All mash pH adjustment assistant software solutions make this presumption.

Wort is indeed more acidic at mash temperature, and thus if it reads ~5.2 pH at mash temperature and ~5.5 pH at 25 degrees C., both readings are factually correct.
 
I think I will stay with your first suggestion Steve and use acid malt. Ps I did us 5.2 for a while but did not have a PH meter to measure at that time whats your thoughts on that stuff Steve?
 
Acid malt provides lactic acid. Back in the days when I was brewing pilsner from pure rainwater I used to add it to the mash to reduce the pH. If you add more than a few ounces to a 5 gallon batch, you can taste it. It's not unpleasant, but it's noticeable.
 
An Ankoù said:
Acid malt provides lactic acid. Back in the days when I was brewing pilsner from pure rainwater I used to add it to the mash to reduce the pH. If you add more than a few ounces to a 5 gallon batch, you can taste it. It's not unpleasant, but it's noticeable.
Click to expand...
I also used narrow range indicator papers, but it's high time I upgraded to a decent pH meter. Can anybody recommend a good reliable model?
 

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