Author Topic: Inconsistent pH readings...  (Read 4470 times)

Offline Pawtucket Patriot

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Inconsistent pH readings...
« on: February 20, 2012, 11:47:24 AM »
I use Bru'n Water to predict my mash pH, in conjunction with actually taking pH readings using ColorpHast strips.  As long as I use +.3 pH correction with the strips, they support Bru'n Water's predicted mash pH 90+% of the time.

Today, I took a pH sample from my IPA mash and the strips indicated a pH of 5.6-5.7 (I almost always shoot for 5.3-5.4).  I was sort of skeptical of this reading, so I tried a second strip.  It ended up reading the same thing.  Out of curiosity, I took a sample of the first runnings and it was dead on at 5.4.  With my limited tech/science knowledge, I can't explain the discrepancy here.  Can someone explain why the sample from the mash might have been higher than the that of the first runnings?  Which one should I trust as an indicator of mash pH?  At this point, I'm more inclined to trust the pH of the runnings sample since it supports Bru'n Water's mash pH prediction.  But maybe the pH of the first runnings should be less than the mash pH?   ???

edit: One more thing -- I brewed almost this same IPA recipe a few months ago with 1% acid malt.  The mash pH was dead on at 5.4.  The only things I changed for today's beer was using a slightly darker English cara malt (approximately 17L darker), and 4% aromatic.  According to Bru'n Water, those changes resulted in a .1 pH drop, so I didn't use any acid malt this time (I use the acid malt ROT that each 1% drops pH by .1).

edit 2: Edited post to clarify that I'm referring to mash pH.
« Last Edit: February 20, 2012, 04:20:33 PM by Pawtucket Patriot »
Matt Schwandt | Minneapolis, MN
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Offline malzig

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Re: Inconsistent pH readings...
« Reply #1 on: February 20, 2012, 06:25:16 PM »
Depending on the particular mash and water combination, the pH can change over the course of the mash.  They're both probably right, it probably just took longer for the pH to equalize due to the dark malts than it did with the lactic acid on the acidulated malt.  It sounds like you're in the right range, though.

Offline Pawtucket Patriot

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Re: Inconsistent pH readings...
« Reply #2 on: February 20, 2012, 06:43:16 PM »
Depending on the particular mash and water combination, the pH can change over the course of the mash.  They're both probably right, it probably just took longer for the pH to equalize due to the dark malts than it did with the lactic acid on the acidulated malt.  It sounds like you're in the right range, though.

This is sort of what I suspect. It should be fine.
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Offline bluesman

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Re: Inconsistent pH readings...
« Reply #3 on: February 20, 2012, 06:55:57 PM »
If you are interested in getting accurate readings down to the tenth as I am, then I recommend buying a pH meter with resolution in that range. I have a Milwaukee MW101 that can be calibrated and is fairly accurate down to the +/- 0.1 range. You will be able to count on your readings whereas pH strips can be a little subjective in their results.

http://www.amazon.com/pH-Meter-Point-Manual-Calibration/dp/B0009YH06Y
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Re: Inconsistent pH readings...
« Reply #4 on: February 20, 2012, 07:19:17 PM »
That meter has been on my wish list for a while. But I just bought a thermapen and I need to wait a little while before I make another gadget purchase.

How are you guys taking mash pH samples anyway?  I just take a tablespoon of wort off the top of the grainbed at the end of the mash. Is there a better method?
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Offline majorvices

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Re: Inconsistent pH readings...
« Reply #5 on: February 20, 2012, 07:24:39 PM »
I think I spent $60-70 on my bench meter. well worth the investments. Those colorpHast strips are trash IMO. I keep some "just in case" something goes wrong with my meter but the color never looks the same as the color key and I just hate 'em.

edit: I just looked at those thermapens. Personally I think your money would have been better spent on a pH meter.
« Last Edit: February 20, 2012, 07:56:39 PM by majorvices »
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Re: Inconsistent pH readings...
« Reply #6 on: February 20, 2012, 08:22:02 PM »
edit: I just looked at those thermapens. Personally I think your money would have been better spent on a pH meter.

Actually, I love the thermapen!  Taking temps is so much quicker and easier with it.  But a pH meter is likely in my hopefully-not-too-distant future. ;)
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Offline narcout

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Re: Inconsistent pH readings...
« Reply #7 on: February 20, 2012, 09:12:43 PM »
I've found that the Colorphast strips read within around .1 of my MW101 (after applying the +.3 correction factor).

How are you guys taking mash pH samples anyway?

When I use the strips, I just dip them in the mash for a few seconds.  When I use my meter, I dip a small tasting glass in the mash and stick it in the freezer for a few minutes until it comes down to an acceptable temperature.

Offline tygo

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Re: Inconsistent pH readings...
« Reply #8 on: February 21, 2012, 05:17:30 AM »
I dip a tall shot glass into the mash, trying to pull a sample with mostly liquid to the extent possible.  Then I chill it down in a 1 qt pyrex measuring cup filled with ice and water.  Just a minute or two of swirling the glass in the ice bath brings the temp right down.  I'm using an MW101.
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Offline majorvices

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Re: Inconsistent pH readings...
« Reply #9 on: February 21, 2012, 05:20:44 AM »
edit: I just looked at those thermapens. Personally I think your money would have been better spent on a pH meter.

Actually, I love the thermapen!  Taking temps is so much quicker and easier with it.  But a pH meter is likely in my hopefully-not-too-distant future. ;)

Priorities man! Getting accurate pH reading is better than a quick temp read.  ;)
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Offline bo

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Re: Inconsistent pH readings...
« Reply #10 on: February 28, 2012, 09:04:06 PM »
The Thermapen is not only quick but very accurate. IMO that's more important than Ph, which is probably not a problem anyway.

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Re: Inconsistent pH readings...
« Reply #11 on: February 28, 2012, 09:16:35 PM »
The Thermapen is not only quick but very accurate. IMO that's more important than Ph, which is probably not a problem anyway.

My $7 lab thermometer is quick enough and 100% accurate - I use it to calibrtate all my installed dial thermometers regularly. I check ph all the time and I am surprised at how often it doesn't check out. YMMV. IN fact I brewed a side batch recently and checked the pH and noticed it was only off a little and the beer never did have a good hot break and the final batch ended up tasting alright but had a stubborn haze. I guess  the mash temp checked out at least.
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Offline bo

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Re: Inconsistent pH readings...
« Reply #12 on: February 28, 2012, 09:26:08 PM »


My $7 lab thermometer is quick enough and 100% accurate -

Unless you check it to something that's NIST traceable, you don't really know.

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Re: Inconsistent pH readings...
« Reply #13 on: February 29, 2012, 05:39:28 AM »
well, I have two of them and if they are both off they are both off the same. I don't have any issues with FG so I feel confident they are fine. I calibrate often, probably not as often as I should. Regardless, I'd rather be off a couple of degrees than have my pH reading off. I give myself a 2 degree leeway on temp anyway just for sanity's sake.

I certainly don't think pH is less important than temperature. They are both obviously important.
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Offline bo

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Re: Inconsistent pH readings...
« Reply #14 on: February 29, 2012, 06:12:38 AM »
I have a cheap digital thermometer that's also very accurate, but I still check it against a glass/mercury standard that is certified.