50 replies to this topic

[matt6150]

Second beer my mash ph was at 5.0 at mash temp. I have a feeling that my mash ph has been pretty dang close all these years without checking it.

[Big Nake]

I am going to muse for a moment about pH and the strips just so I am clear on my understanding.

 

According to Water the proper room temp. pH is 5.2-5.6. Because pH drops as you heat it the proper pH at mash temp is 0.2 lower than at room temperature giving you a proper mash temp pH of 5.0-5.4. Correct?

 

Now the colorpHast strips will give you lower reading than actual (at room temp.) by a factor of 0.3. Kai documented this clearly on his website. So proper room temp pH with these strips should show 4.9-5.3. However he says nothing there about using the strips at mash temp. and what you should expect. Theoretically you would expect the strips to give you 4.7-5.1 for proper pH at mash temp. but the quote Studs provided from Kai on HBT is throwing me off. "[color=rgb(40,40,40);font-family:helvetica, arial, sans-serif;font-size:12px;background-color:rgb(247,247,247);]the strips have the same color [/color][color=rgb(40,40,40);font-family:helvetica, arial, sans-serif;font-size:12px;background-color:rgb(247,247,247);]reaction[/color][color=rgb(40,40,40);font-family:helvetica, arial, sans-serif;font-size:12px;background-color:rgb(247,247,247);] at mash and room temp."[/color]

It's the first I have seen of this. If it is true, the proper mash temp pH as measured on the strips should be 4.9-5.3 right? for you guys who just dip them in the mash are you leaving them in there at that temp for the entire 2 minutes recommended on the case? 

When I used the strips (which was way, way back in September 2013), I would typically look for a color that represented 5.0 on the key which would translate to a pH of 5.3 which I would call "good".

 

 

ken, i think using your meter in really hot liquid will shorten the probe life.  could be wrong on that.

Check out post #35 and get back to me. 

 

 

Yes if it's an ATC meter. Take a sample at, say, 120°F then let it cool down to room temp and you'll see that it's higher.

Okay, you're tormenting me now.  My understanding was that the pH is the pH and the temp is not a factor because the meter is doing automatic temp compensation for you.  So the reading at 120° will be the same as the reading at 70° (as far as the display on the meter goes...) because the meter is compensating for the temp differential.  Right?  Otherwise, what is ATC for?  If the pH shows 5.3 at 120°, are you saying that when it gets to 70°, the pH will show 5.5 or something?  As I leave my meter in my sample and as the temp drops, the pH stays the same... in my very brief experience with this meter.

[MtnBrewer]

Okay, you're tormenting me now.  My understanding was that the pH is the pH and the temp is not a factor because the meter is doing automatic temp compensation for you.  So the reading at 120° will be the same as the reading at 70° (as far as the display on the meter goes...) because the meter is compensating for the temp differential.  Right?  Otherwise, what is ATC for?  If the pH shows 5.3 at 120°, are you saying that when it gets to 70°, the pH will show 5.5 or something?  As I leave my meter in my sample and as the temp drops, the pH stays the same... in my very brief experience with this meter.

Go back to my previous post where I said this was specifically NOT temperature compensation.ATC corrects for errors within the meter itself. But pH is temperature dependent so the pH you read will change with temperature. In other words, if your meter has ATC, then the pH you read will be the actual pH of the sample. But the actual pH of the sample changes with temperature.

[Brauer]

Don't forget to account for the built in error you get from the ColorpHast strips. They will read 0.3-0.35 lower than actual pH at room temperature.

 

 

Yeah I did remember that, thanks! Why is that btw, they don't say this anywhere when you buy them. Where does this info come from?

It is an error that is inherent to the strips that was established through empirical comparison to pH meter readings of wort.  The strips are correct if you allow for this 0.3 low reading.  

 

The reason they don't change with temperature is that they are meant to be used at RT, because the chemical reaction gets thrown off at higher temperatures.  However, conveniently for brewers, the error coincidentally parallels the actual change in pH with temperature, meaning that at RT or mash temp a reading of 5.0 is a mash pH of 5.3.

 

I am going to muse for a moment about pH and the strips just so I am clear on my understanding.

 

According to Water the proper room temp. pH is 5.2-5.6. Because pH drops as you heat it the proper pH at mash temp is 0.2 lower than at room temperature giving you a proper mash temp pH of 5.0-5.4. Correct?

 

Now the colorpHast strips will give you lower reading than actual (at room temp.) by a factor of 0.3. Kai documented this clearly on his website. So proper room temp pH with these strips should show 4.9-5.3. However he says nothing there about using the strips at mash temp. and what you should expect. Theoretically you would expect the strips to give you 4.7-5.1 for proper pH at mash temp. but the quote Studs provided from Kai on HBT is throwing me off. "[color=rgb(40,40,40);font-family:helvetica, arial, sans-serif;]the strips have the same color [/color][color=rgb(40,40,40);font-family:helvetica, arial, sans-serif;]reaction[/color][color=rgb(40,40,40);font-family:helvetica, arial, sans-serif;] at mash and room temp."[/color]

It's the first I have seen of this. If it is true, the proper mash temp pH as measured on the strips should be 4.9-5.3 right? for you guys who just dip them in the mash are you leaving them in there at that temp for the entire 2 minutes recommended on the case? 

Ignore the pH at mash temperature, that is not what they mean by mash pH.  pH is traditionally read at RT, so mash pH is the pH after cooling to RT. a 5.0-5.3 reading on the strips is a mash pH of 5.0-5.6.

 

When I used the strips (which was way, way back in September 2013), I would typically look for a color that represented 5.0 on the key which would translate to a pH of 5.3 which I would call "good".

 

 

Check out post #35 and get back to me. 

 

 

Okay, you're tormenting me now.  My understanding was that the pH is the pH and the temp is not a factor because the meter is doing automatic temp compensation for you.  So the reading at 120° will be the same as the reading at 70° (as far as the display on the meter goes...) because the meter is compensating for the temp differential.  Right?  Otherwise, what is ATC for?  If the pH shows 5.3 at 120°, are you saying that when it gets to 70°, the pH will show 5.5 or something?  As I leave my meter in my sample and as the temp drops, the pH stays the same... in my very brief experience with this meter.

 

No. A reading taken at 100-120F will be wrong (low) by about 1.4 pH.  

Go back to my previous post where I said this was specifically NOT temperature compensation.ATC corrects for errors within the meter itself. But pH is temperature dependent so the pH you read will change with temperature. In other words, if your meter has ATC, then the pH you read will be the actual pH of the sample. But the actual pH of the sample changes with temperature.

Absolutely.  I tried to say it better myself and couldn't.

[positiveContact]

The reason they don't change with temperature is that they are meant to be used at RT, because the chemical reaction gets thrown off at higher temperatures.  However, conveniently for brewers, the error coincidentally parallels the actual change in pH with temperature, meaning that at RT or mash temp a reading of 5.0 is a [color=#ff0000;]RT[/color] mash pH of 5.3.

 

for clarification: did you mean to say this? (bold and in red)

Edited by TheGuv, 30 October 2013 - 04:28 AM.

[Brauer]

for clarification: did you mean to say this? (bold and in red)

No. Good catch, I meant to say a reading of 5.3 is 5.0.

[neddles]

No. A reading taken at 100-120F will be wrong (low) by about 1.4 pH.  

Lots of good information this morning, thanks. I have to ask though, how did you derive 1.4pH?

[positiveContact]

No. Good catch, I meant to say a reading of 5.3 is 5.0.

 

which is why I check my mash pH at mash temperature and add 0.3 to it and shoot for a corrected value of around 5.3.  hopefully i haven't been doing this backwards for all of this time.  i still don't get why the strips are like this but it's convenient that I don't have to cool a sample off to use them.

[Brauer]

Lots of good information this morning, thanks. I have to ask though, how did you derive 1.4pH?

Man, I shouldn't have posted as I was trying to get out the door this morning. That's also wrong. It should be 0.14. That's an interpolation to 120F based on a 0.2 pH drop from RT to 150F.

Edited by Brauer, 30 October 2013 - 07:14 AM.

[Brauer]

which is why I check my mash pH at mash temperature and add 0.3 to it and shoot for a corrected value of around 5.3. hopefully i haven't been doing this backwards for all of this time. i still don't get why the strips are like this but it's convenient that I don't have to cool a sample off to use them.

The color is the result of a chemical reaction that is affected by both pH and temperature (pretty commonl for a chemical reaction) and the pH is affected by temperature. It's just coincidental that the effects negate each other in this pH range.

[positiveContact]

The color is the result of a chemical reaction that is affected by both pH and temperature (pretty commonl for a chemical reaction) and the pH is affected by temperature. It's just coincidental that the effects negate each other in this pH range.

 

ah ha!  hopefully it sticks this time.