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General Category => Ingredients => Topic started by: Hokerer on January 09, 2010, 11:48:41 PM

Title: Correctly reading ph test strips
Post by: Hokerer on January 09, 2010, 11:48:41 PM
Ok, I've seen all the discussion about the difference between ph at mash temp and at room temp... also the discussion of the test strips reading about 0.3 hi/lo.  And now I'm confused.

I wait at least 10 minutes after dough-in, collect a small sample that is, as much as possible, just liquid, let it cool to ambient temp, and then check it with the test strip.  Say I read 5.8.  Does that mean the mash ph was 5.5? (subtract 0.3 for temperature)...  or was it 5.2? (subtract 0.3 for temp and another 0.3 for strip inaccuracy)... or was it 5.8? (subtract 0.3 and then add 0.3)...  or am I adding when I should be subtracting or what?

Also, if ph differs at the different temperatures, when they say 5.2 is ideal, what temp is that at?
Title: Re: Correctly reading ph test strips
Post by: lupy on January 10, 2010, 06:36:54 AM
I claim no first hand knowledge but according to Kai;
"In the end it was confirmed that the colorpHast strips have a -0.3 systematic error when they are used for testing the mash pH." "I.e. the strips tend to report a pH reading that is about 0.3 pH less than what is determined with a calibrated pH meter"
http://braukaiser.com/wiki/index.php?title=An_Evaluation_of_the_suitability_of_colorpHast_strips_for_pH_measurements_in_home_brewing (http://braukaiser.com/wiki/index.php?title=An_Evaluation_of_the_suitability_of_colorpHast_strips_for_pH_measurements_in_home_brewing)
Title: Re: Correctly reading ph test strips
Post by: Hokerer on January 10, 2010, 07:46:02 PM
"I.e. the strips tend to report a pH reading that is about 0.3 pH less than what is determined with a calibrated pH meter"

Ok, got that part.  So above, when I read 5.8 with the strip, that really means 6.1?  Still leaves what do I do about the temp?  The ph at mash temp is supposedly 0.3 off from the ph at ambient.  Do I add or subtract 0.3?  Ultimately, I guess I want to find out how from the magical 5.2 I am so I can see which direction to adjust things, right?
Title: Re: Correctly reading ph test strips
Post by: a10t2 on January 10, 2010, 09:32:44 PM
Mash pH readings are (or at least should be) reported with the assumption that the sample is cooled. So you want to read roughly 5.5 at room temp, which is about 5.2 at mash temp.

Of course, for your own measurements you can do it either way, as long as you're consistent.
Title: Re: Correctly reading ph test strips
Post by: brewbeard on January 11, 2010, 02:02:54 AM
To make things more confusing, the ColorpHast strips are not affected by temperature. For some reason, the will always read a room temperature pH. A strip dipped in the mash at room temperature and at mash temperature will look exactly the same. Kai noticed this, I tried it for myself and noticed the same thing.


Essentially follow this with the ColorpHast strips:

Regardless of the temperature, try to target a pH between 5.1 and 5.4 on the strip.


You can just dip the pH strip in the mash and take a reading. Adjust if it looks like it is out of this range.
Title: Re: Correctly reading ph test strips
Post by: Kaiser on January 11, 2010, 02:04:07 AM
The aforementioned article is still under construction because I'm planning to add exactly that. But based on my obsevations so far, the pH strip reading is independent of mash temp. That means: even a strip placed in a hot mash will give a reading that is about 0.3 lower than the mash's room temp pH.

I plan to take some pictures but haven't gotten around to that yet.

Kai
Title: Re: Correctly reading ph test strips
Post by: Hokerer on January 11, 2010, 03:23:16 AM
will give a reading that is about 0.3 lower than the mash's room temp pH.

So since that is room temp pH and mash temp pH is about 0.3 lower than room temp pH does that mean that the reading on the strip ends up being equal to the mash temp pH?  and it's the mash temp pH that we're targeting to be 5.2?
Title: Re: Correctly reading ph test strips
Post by: Kaiser on January 11, 2010, 03:59:03 AM
I don't exactly know where this 5.2 mash pH target comes from. The literature I read indicates that 5.4-5.6 is a better target. Those numbers, however, are for room temp samples.

Kai
Title: Re: Correctly reading ph test strips
Post by: Thirsty_Monk on January 11, 2010, 05:52:41 PM
A strip dipped in the mash at room temperature and at mash temperature will look exactly the same. Kai noticed this, I tried it for myself and noticed the same thing.


Essentially follow this with the ColorpHast strips:

Regardless of the temperature, try to target a pH between 5.1 and 5.4 on the strip.


You can just dip the pH strip in the mash and take a reading. Adjust if it looks like it is out of this range.

Strip dipped into boiling wort will ehmm... melt.  :-[ Ask me how I know.
Title: Re: Correctly reading ph test strips
Post by: tygo on January 13, 2010, 05:35:40 PM
I don't exactly know where this 5.2 mash pH target comes from. The literature I read indicates that 5.4-5.6 is a better target. Those numbers, however, are for room temp samples.

Kai

So if 5.4 - 5.6 is the target, and that's at room temperature, then the pH at mash temperature that's being targeted is 5.1 - 5.3.  Is that right?
Title: Re: Correctly reading ph test strips
Post by: ndcube on January 13, 2010, 05:50:06 PM
I don't exactly know where this 5.2 mash pH target comes from. The literature I read indicates that 5.4-5.6 is a better target. Those numbers, however, are for room temp samples.

Kai

So if 5.4 - 5.6 is the target, and that's at room temperature, then the pH at mash temperature that's being targeted is 5.1 - 5.3.  Is that right?

That's my understanding.  So the buffer 5.2 product should bring your pH to 5.5 at room temp...
Title: Re: Correctly reading ph test strips
Post by: denny on January 13, 2010, 05:56:55 PM
So the buffer 5.2 product should bring your pH to 5.5 at room temp...

It should, but it may not.
Title: Re: Correctly reading ph test strips
Post by: ndcube on January 13, 2010, 06:11:39 PM
So the buffer 5.2 product should bring your pH to 5.5 at room temp...

It should, but it may not.

Right.  I guess I was just making a point to why it was called 5.2 and not 5.5.
Title: Re: Correctly reading ph test strips
Post by: a10t2 on January 13, 2010, 06:12:06 PM
It should, but it may not.

I would amend that to say "probably won't". Buffers, pretty much by definition, can only adjust the pH to a target if it's within a certain range to begin with. I used the 5.2 product for about half a dozen batches, then I bought some pH strips and discovered that it doesn't actually work very well - and I was already getting my water "close" and only using the buffer to dial it in.
Title: Re: Correctly reading ph test strips
Post by: Thirsty_Monk on January 14, 2010, 03:07:03 AM
I don't exactly know where this 5.2 mash pH target comes from. The literature I read indicates that 5.4-5.6 is a better target. Those numbers, however, are for room temp samples.

Kai

So if 5.4 - 5.6 is the target, and that's at room temperature, then the pH at mash temperature that's being targeted is 5.1 - 5.3.  Is that right?
If I get lucky my mash with colorpHast at room temp reads 5.3.
Normally it reads 5.0
Title: Re: Correctly reading ph test strips
Post by: Hokerer on January 14, 2010, 03:15:09 AM
If I get lucky my mash with colorpHast at room temp reads 5.3.
Normally it reads 5.0

So, if I understand all this discussion, the strip reading 5.3 at room temp (means 5.0 at mash temp) is lower than you would want.  Have you ever experimented with adding chalk or baking soda (both of which I think would raise the ph) to get your reading into the 5.4 to 5.6 range at room temp?
Title: Re: Correctly reading ph test strips
Post by: blatz on January 14, 2010, 03:19:01 AM
If I get lucky my mash with colorpHast at room temp reads 5.3.
Normally it reads 5.0

So, if I understand all this discussion, the strip reading 5.3 at room temp (means 5.0 at mash temp) is lower than you would want.  Have you ever experimented with adding chalk or baking soda (both of which I think would raise the ph) to get your reading into the 5.4 to 5.6 range at room temp?

nope - what's being said is that the strips read the same at room and mash temp (no difference) and read 0.3 low, so the 5.3 likely is 5.6.
Title: Re: Correctly reading ph test strips
Post by: tygo on January 14, 2010, 03:23:30 AM
I'm going to take my cheap Milwaukee ph600 for a test run this weekend on a stout.  I think I'll make some light mineral additions to the mash right off the bat, 2g CaCl and 2g chalk, based on my home water profile and then see what the pH looks like.  I'll just shoot for the 5.5 room temperature reading and see where I end up.  If I need to raise the pH more I'm going to add equal proportions of both the salts in 2g increments until I get there.
Title: Re: Correctly reading ph test strips
Post by: Hokerer on January 14, 2010, 03:30:40 AM
Nope - what's being said is that the strips read the same at room and mash temp (no difference) and read 0.3 low, so the 5.3 likely is 5.6.

Dang, forgot the 0.3 low.  How's this?  The reading on the test strip, whether tested at room temp or mash temp, will correspond to the "mash temp ph" which should be targeted to be between 5.1 and 5.4.

Then his 5.3 is a good reading.
Title: Re: Correctly reading ph test strips
Post by: Thirsty_Monk on January 14, 2010, 03:51:13 AM
If I get lucky my mash with colorpHast at room temp reads 5.3.
Normally it reads 5.0

So, if I understand all this discussion, the strip reading 5.3 at room temp (means 5.0 at mash temp) is lower than you would want.  Have you ever experimented with adding chalk or baking soda (both of which I think would raise the ph) to get your reading into the 5.4 to 5.6 range at room temp?
Yes I am playing with salts.
I think I get good conversion (about 80% brewhouse eff).
I am still little bit confused what all that means.
I have been measuring pH for about of 1/2 year.