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Home Brew Forums > Home Brewing Beer > Brew Science > Proper use of a pH meter
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Old 11-19-2010, 04:20 PM   #11
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Originally Posted by EvilBrewer View Post
Hi, AJ,

I used your primer for a recent batch of an APA:
- 9lb American 2-row
- 1.5lb cara-pils
- 0.22lb sauermalz (roughly 2% of grain bill as per your advice)
- 1.25 oz Cascade (60min)
- 1.75 oz Cascade (1min)
- 1056 yeast w/starter
- 1 tsp CaCl2 per 5 gallons
- 1/4 tsp CaSO4 per 5 gallons

This actually overshot the acidity a bit. The mash pH was around 4.8. No worries...I will reduce the sauermalz next time.
I have to question the measurement. You have nearly a pale malt only mash and the pH of those is reasonably easy to predict. I question the measurement especially since:

Quote:
but it's like the malt and hops are somehow muted.
You have described the classic quality of a beer with too high of a pH.
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Old 11-19-2010, 04:41 PM   #12
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I have to question the measurement. You have nearly a pale malt only mash and the pH of those is reasonably easy to predict. I question the measurement especially since:



You have described the classic quality of a beer with too high of a pH.
That's fine but I'm pretty sure my measurements were accurate? Here's what I did:

Also..I will assume you've noted the sauermalz in my grain bill, which as you know lowers pH. As for the measurement itself, I calibrated with 7.01 and 4.01 solutions moments before my mash pH measurements.

I literally removed the pH meter from the buffer solution, rinsed with distilled water and then proceeded to take measurements of the mash (cooled to room temp). I checked the calibration of the pH meter afterward and it was still accurate.

I didn't strain off the grains when measuring...so it was kind of like putting my pH meter into 70F oatmeal. That doesn't matter though does it?
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Old 11-19-2010, 05:39 PM   #13
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Originally Posted by EvilBrewer View Post

....

This actually overshot the acidity a bit. The mash pH was around 4.8. No worries...I will reduce the sauermalz next time.
Something doesn't seem quite right here. If you mash base malt with DI water you should get a pH around 5.75 or so. Adding as much calcium as you did might be expected to lower it to 5.65 and the caramel malt might lower it another tenth at most depending on the particular malt to 5.55. Now using the rule of thumb for sauermalz 2% should drop 0.2 further to 5.35. You came in 0.55 below that and it doesn't compute. I've often seen the pH in a mash like the one you describe come out at 5.05 or 5.1 but after a few minutes it starts to climb and eventually settles in at 5.4 - 5.5. But you said it hung in there at 4.8 for the duration. Again, something doesn't seem right.


I didn't strain off the grains when measuring...so it was kind of like putting my pH meter into 70F oatmeal. That doesn't matter though does it?

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Originally Posted by EvilBrewer View Post
I tried to add some baking soda to bring it up, but I guess I didn't add enough and I was a little afraid of completely ruining the batch (that, on top of the fact that time was ticking away and by the time I'd cooled the third mash sample to room temp, it was like 15 minutes into the mash)...so I just figured I'd run with what I had. And that was a pretty solid 4.8 throughout the mash.
This is suspicious too. Baking soda is highly soluble and should result in an immediate increase in pH unless the amount you added was just too miniscule.



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Originally Posted by EvilBrewer View Post
Maybe I just need to be patient and let it age?

I guess my question is this: could these factors be a result of the lower than optimal pH??

Definitely let it age some. But in the interim try to resolve why the pH reading was so low. First step would be a buffer check (not recalibration). Just dunk the meter in 4 and 7 buffer (with DI rinse in between) and see what you get for readings. Then recalibrate and try measuring the pH of a test mash (same relative amount of base malt, same relative amount of cara) with DI water. Now add the calcium chloride and sulfate, stir and look for the change in pH. Some time for reaction should be allowed to pass. Finally add the sauermalz. If the pH winds up at 4.8 then I'll be surprised (I still get surprises from time to time) but at least you will have verified that the problem is indeed too much sauermalz. Perhaps the sauermalz you obtained had appreciably more lactic content than the nominal 2% w/w.

Since you have a pH meter you don't have to rely on the sauermalz guidelines in the Primer. Mash with the water treated to the 5 grams/5 gallon CaCl2 level and check pH. Have some sauermalz pre-ground and ready to go and add it if the pH is higher than you want. Do this incrementally so you don't overshoot the target. With a bit of experience you should have a pretty good idea of how much sauermalz is required for a particular beer and the pH measurement then becomes a check.

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I didn't strain off the grains when measuring...so it was kind of like putting my pH meter into 70F oatmeal. That doesn't matter though does it?
Shouldn't - that's the way I do it. If a piece of grain husk or non dissolved starch particle blocked the reference junction that could be an explanation as to why the pH read low and didn't change. Its a good idea to blast the business end to the electrode with a stream of DI water as from, for example, a wash bottle to be sure everything is rinsed off and the ref. junction is clear.
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Old 11-19-2010, 07:25 PM   #14
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Something doesn't seem quite right here.
~sigh~
Yeah sounds like it. Man, this is frustrating.


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Originally Posted by ajdelange View Post
This is suspicious too. Baking soda is highly soluble and should result in an immediate increase in pH unless the amount you added was just too miniscule.
I only added 1 gram of Baking Soda. I was paranoid that it would ruin my batch and was afraid to add more


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Originally Posted by ajdelange View Post
Definitely let it age some. But in the interim try to resolve why the pH reading was so low. First step would be a buffer check (not recalibration). Just dunk the meter in 4 and 7 buffer (with DI rinse in between) and see what you get for readings. Then recalibrate and try measuring the pH of a test mash (same relative amount of base malt, same relative amount of cara) with DI water. Now add the calcium chloride and sulfate, stir and look for the change in pH. Some time for reaction should be allowed to pass. Finally add the sauermalz. If the pH winds up at 4.8 then I'll be surprised (I still get surprises from time to time) but at least you will have verified that the problem is indeed too much sauermalz. Perhaps the sauermalz you obtained had appreciably more lactic content than the nominal 2% w/w.
I will conduct these tests this weekend...

The acidulated malt I used was Weyermann so that's probably not the culprit; my guess is that it's something I'm doing. Usually is the case! I will post my results ASAP.

Thanks for the advice.
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Old 11-25-2010, 02:34 AM   #15
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I will conduct these tests this weekend...will post my results ASAP.
AJ, et al.,

Okay, so I did a 1/10th sized version of this batch. The amounts are as follows...

** Original **
9 lb 2-row
1.5 lb carapils
0.22 Acidulated
3.5 gallon strike water
0.7 g CaSO4
2.4g CaCl2

** 1/10th batch **
0.9 lb 2-row
0.15 lb carapils
0.022 (10grams) Acidulated
0.35 gallons strike water (~1325 grams)
0.07 g CaSO4
0.24g CaCl2

pH Results from 1/10th batch:
-Doughed in with just 2-row and carapils, waited 5 minutes and measured pH (pH = 5.47)
-Added acidulated malt, waited 5 more minutes and measured pH (pH = 5.28)
-Measured pH at end of mash (pH = 5.38)

So, this seems more in line with your predictions, AJ. But I still can't figure out what went wrong on my brew day (see pH measurements/concerns in earlier post in this thread). The main difference between actual and test (aside from the proportions) is the equipment. On brew day, I used my 10 gallon Igloo MLT. For the 1/10th batch, I used a plastic bowl placed inside a small cooler for insulation. Temperature regulation was about the same for both. So, it's got me a little worried about my equipment...could my Igloo MLT be throwing off the pH somehow? I've not read anything about this but at this point I'm just searching for any flaw in my process.

The beer from my brew day is drinkable but it's not that good. It's very grainy tasting and the flavors of the malt and hops are very muted as I mentioned earlier. Slight astringency. Apparently these are characteristics of a high mash pH, but on brew day the measurements all came out much *lower* than optimal. Could these taste characterstics possibly be a result of low pH? It's also possible that my pH meter is junk even though I calibrate it every time it's used. I'm at a loss here.
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Old 11-27-2010, 02:31 PM   #16
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Could these taste characterstics possibly be a result of low pH? It's also possible that my pH meter is junk even though I calibrate it every time it's used. I'm at a loss here.
I'm guessing it is neither. You wouldn't be the first guy to get led down the garden path by a pH meter nor are you likely to be the last. I don't know how much experience you have with these things but please believe me when I say that experience is important. There is a bit of an art to pH measurement and experience is the only way to acquire it. When I wrote a few posts back WRT to the numbers you got that something didn't seem right that statement was based on nothing but experience. If I read 4.8 based on the mash you described I would distrust that reading based on experience and do the checks I recommended in order to find out what was wrong. With time you will know to do the same. Based on the failure of the pH reading to respond to the addition of bicarbonate I'd guess blockage of the reference frit by a particle of mash (husk?) material but of course it could have been something else. In the sense that an electrode with its reference junction blocked is going to give you a bum reading I suppose it is "junk", as long as the blockage exists, but once the blockage is reduced it will (and apparently has) become functional again.

So my advice is to take lots of pH readings not only at dough in but before the boil, after the boil (all cooled, of course), a few hours after pitching, throughout the progress of fermentation (until pH stops dropping) and finally of the finished beer. Record all these readings. You'll learn a lot and, more to the point, you'll get familiar with your instrument.
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Old 11-27-2010, 02:56 PM   #17
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In the sense that an electrode with its reference junction blocked is going to give you a bum reading I suppose it is "junk", as long as the blockage exists, but once the blockage is reduced it will (and apparently has) become functional again.
Yeah...this seems like the most obvious explanation. I did keep a spray bottle of DI water handy during my experiment like you suggested. I blasted the electrode a couple of times to get rid of any husks that were stuck up in there. Incidentally, the numbers came out as predicted...go figure

I can't say for sure it was the same problem during my brew day (in which the numbers were out of whack) but like I said...seems like the most obvious explanation.

The taste of the batch still concerns me. Based on the numbers that I got during my experiment, and given that the experiment was intended to mimic the brew day batch, I can assume the actual mash pH of my brew day was in the neighborhood of 5.2-5.3, which is in the optimal range as far as I understand. And yet the beer is not very good. Grainy, slightly astringent. Generally kind of bland. One of the posters said earlier that it was classic characterstics of a mash with too HIGH of a pH.

Any thoughts there? Should I be shooting for a lower mash pH range?
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Old 11-27-2010, 03:19 PM   #18
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pH isn't the only factor in brewing good beer. It's a sine qua non for sure but it's not the whole story. If you are getting pH in the 5.2 - 5.5 region then you have pH under control (IMO) and you can cross that one off your list of concerns. But in any case I think you should let the beer age for a month before you judge it. All beers improve with "lagering".

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Old 12-21-2010, 07:01 PM   #19
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...I think you should let the beer age for a month before you judge it. All beers improve with "lagering".
Just wanted to follow up...this beer is about 6.5 weeks old now and it's pretty good. I'm pretty sure I'm tasting some tannins, but it doesn't completely overpower the complexity of the malt and hops like in previous batches. It's definitely the best pale ale that I've ever brewed, and probably one of the best overall. That's pretty huge; I consider myself to be very discerning with the beers I brew.

I've done another batch of the exact recipe since then and I'm thinking it will be even better..was able to measure pH more accurately and it was in the proper range throughout the mash. I also increased the grain bill and intentionally under-sparged. OG came out the same as previous batch so it should be an apples-to-apples comparison. My theory is that I had been over-sparging my grain and extracting tannins...we shall see.

Anyway thanks for the advice guys!
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