Water Chemistry: mash pH calculator

General discussion on BeerTools Pro Software.

Water Chemistry: mash pH calculator

Postby rrosa » Sun Jun 24, 2007 11:04 pm

I usually use soft water, add calcium chloride, gypsum, and 5.2 Mash stabilizer, and that should be good enough, but now I would like to play a little bit trying to mimic some water profiles, just for fun.

I have read Chapter 15 in John Palmer's book and looked at the Beer Tools Pro Water Chemistry Calculator and I am a little bit confused. The corresponding predicted values do not agree and it is not clear what pH is given. And as I understand from John Palmer, the mash pH at mash temperature should be between 5.2 and 5.6, and the drop in pH from room temperature to mash temperature is about .35, right? So my main questions are the following:

1) How is the mash pH calculated in Beer Tools Pro? (It doesn't seem to agree with John Palmer's nomograph.)

2) Is it given in room temperature or mash temperature? (It seems it is at room temperature.)

3) Is it the expected pH after addition of base malt or before that? (I assume it is after the addition of base malt, just want to make sure.)
Ricardo - http://cervejarte.org/blog
MacBook 2GHz Intel Core 2 Duo 2Gb SDRAM running Mac OS X Snow Leopard 10.6.8
User avatar
rrosa
Pale Ale
Pale Ale
 
Posts: 55
Joined: Mon Jan 15, 2007 9:32 pm
Location: Rio de Janeiro

Postby rrosa » Fri Jun 29, 2007 12:27 am

Okay, no answer. Let me try to be more specific now that I've read some books more carefully. And I apologize in advance for the long and technical post, and for any stupid thing I might say for my background is not chemistry.

In BTP's Water Profile, Alkalinity seems to be given in terms of ppm of CaCO3, right? And this is somehow related to the concentration of HCO3, although the equilibrium concentration depends on the pH. For "normal" brewing pH and not too small concentrations this relation seems to be close to 1.22 but it varies a little bit and changes dramatically when pH is too high or too low or their concentration is too small. A value near 1.22 seems to be used by Palmer in his nomograph. Okay, I could work with 1.22 and neglect the extreme cases, but I am curious to know the exact relation, if possible.

Now for the Residual Alkalinity (RA) shown in the Water Chemistry window. I look at Ray Daniels' "Designing Great Beers", George Fix's "Principles of Brewing Science", John Palmer's "How to Brew", Randy Mosher's "The Brewers Companion", Ted Goldammer's "The Brewers Handbook", and Michael Lewis "Stout - Classic Beer Styles" and I don't quite seem to find an agreement. For the sake of explanation Fix and Goldammer ignore the contribution of Calcium, which is the most important of the two ions for practical purposes, so that is not very helpful. Daniels talks about RA but doesn't give the formula for it, it goes directly to the formula for the pH. Palmer gives the formula for RA in milliequivalents and a nomograph in ppm. Analysing the nomograph I can deduce the following approximate relation:
[RA] = [CaCO3] - 0.7*[Ca] - 0.6*[Mg],
all concentrations [ ] in ppm, with [CACO3] dubbed the Alkalinity. The part [EH]=0.7*[Ca]+0.6*[Mg] is called the Effective Hardness by Palmer. Using the approximate relation [CACO3]=[HCO3]/2.2 mentioned above I get pretty close to what BTP displays as Residual Alkalinity. I could be happy with that, but let us not stop there.

In milliequivalents, the formula in Palmer is
[[RA]] = [[CaCO3] - [[Ca]]/3.5 - [[Mg]]/7
I don't know how to convert that to ppm, but Mosher and Lewis give some hints for that:
[[Ca]]=[Ca]/20, [[Mg]]=[Mg]/12, [[CaCO3]]=[CaCO3]/50, [[RA]]=[RA]/50.
Then, we find
[RA] = [CaCO3] - 0.714285*[Ca] - 0.595238*[Mg]
Is that correct?

Now how do I get the predicted pH from the RA? Once again from Palmer's nomograph I can deduce the formula
pH = 5.7 + 0.0016667*RA,
but BTP seems to start at 5.8, being more closely approximated by
pH = 5.8 + 0.0016667*RA.
The starting value 5.8 seems to agree with Daniels formula
pH = 5.8 + 0.028*( 0.056*[CaCO3]-0.04*[Ca]-0.033*[Mg] )
= 5.8 + 0.001568*([CaCO3]-0.714285*[Ca]-0.589285*[Mg] )
From this last relation it seems reasonable to deduce that Daniels formula for the Residual Alkalinity would be
RA = [CaCO3]-0.714285*[Ca]-0.589285*[Mg],
which is very close to Palmer's, but, using again [CACO3]=[HCO3]/2.2, this doesn't quite seem to agree with BTP, although it is pretty close.

And last but not least, besides Palmer's lower pH prediction of 5.7 when RA=0, he also mentions that this pH is for the mash at room temperature and that at mash temperature this should be .35 pH less, i.e. pH=5.35!? This seems too good, right were we want it, and nowhere else I saw any mention to the temperature of the mash when speaking about pH. And this is in fact my most important questions.

So, I can summarize the above questions as
1) Is the Alkalinity in BTP the ppm value of CaCO3?
2) What is the precise relation between Alkalinity, pH and the concentration of HCO3 in BTP's Water Profile?
3) What is the precise formula for Residual Alkalinity in BTP?
4) What is the precise formula for the predicted pH in BTP?
5) At what temperature is the pH predicted in BTP?
Ricardo - http://cervejarte.org/blog
MacBook 2GHz Intel Core 2 Duo 2Gb SDRAM running Mac OS X Snow Leopard 10.6.8
User avatar
rrosa
Pale Ale
Pale Ale
 
Posts: 55
Joined: Mon Jan 15, 2007 9:32 pm
Location: Rio de Janeiro

RA okay. pH?

Postby slothrob » Fri Jun 29, 2007 11:52 am

I'm not going to anwswer any of your questions, because I can't, but I thought I'd tell you what I did, as I took a somewhat different approach in assessing BTP's water calculator.

1) I chose my water, then played with the redipe, changing the SRM dramatically.
I found that SRM had no effect on the value listed as "Mash pH" in BTP.
I don't know what this pH is, but if it doesn't change with SRM, so I have no idea how I would use it. Frankly, I ignore it.

2) For RA, on the other hand, I found that BTP calculated RA's that were virtually identical to those I got from Palmer's Nomograph and spreadsheet. So, I use BTP to calculate my RA and let Palmer tell me what RA I should have for my predicted SRM.
BTP v2.0.* Windows XP
User avatar
slothrob
Moderator
Moderator
 
Posts: 1768
Joined: Mon Apr 10, 2006 1:36 pm
Location: Greater Boston

Postby rrosa » Fri Jun 29, 2007 12:16 pm

Thanks, slothrob!

My guess is that BTP's predicted pH is for a 100% base-malt mash.

The formulas are not so important, it is just that I am a mathematician and "need" to know...

What puzzles me more are Palmer's pH starting value of 5.7 (for zero RA) instead of the more common value of 5.8 seen in the literature and in BTP, and, even more importantly, the issue that this pH is for mash at room temperature, with the pH dropping by 0.35 at mash temperature, which I saw nowhere else.
Ricardo - http://cervejarte.org/blog
MacBook 2GHz Intel Core 2 Duo 2Gb SDRAM running Mac OS X Snow Leopard 10.6.8
User avatar
rrosa
Pale Ale
Pale Ale
 
Posts: 55
Joined: Mon Jan 15, 2007 9:32 pm
Location: Rio de Janeiro

pH and temperature

Postby slothrob » Fri Jun 29, 2007 1:08 pm

If you want to try and figure out if the pH change is correct, look up the Nernst Equation. I've never tried to calculate if the 0.35 pH change is correct. I've seen it mentioned a lot, but that's probably due to the influence of Palmer's book. The pH will definately drop, though, whenever the temperature is increased.

The ph 5.7 vs. 5.8 is probably due to the fact that the ideal mash pH is actually a range of 0.1 or so. Palmer's 5.7 may just reflect a preference of his to aim for the lower end of the reange instead of the higher end. As a guess, that may be to steer people away from the "dangerous" high end of the range where tannins may be extracted.
BTP v2.0.* Windows XP
User avatar
slothrob
Moderator
Moderator
 
Posts: 1768
Joined: Mon Apr 10, 2006 1:36 pm
Location: Greater Boston

Postby rrosa » Fri Jun 29, 2007 9:53 pm

Apparently the Nernst equation is only to correct for the pH reading through electrode, it is not really related to the change in the actual pH. But I did some more googling and found further support to the drop in pH when going from room temp to mash temp, with the drop varying around the value of 0.3. Ok, I should be happy with that. Thanks again!
Ricardo - http://cervejarte.org/blog
MacBook 2GHz Intel Core 2 Duo 2Gb SDRAM running Mac OS X Snow Leopard 10.6.8
User avatar
rrosa
Pale Ale
Pale Ale
 
Posts: 55
Joined: Mon Jan 15, 2007 9:32 pm
Location: Rio de Janeiro

pH and Temperature

Postby slothrob » Sat Jun 30, 2007 10:56 am

Yeah, I misunderstood what the Nerst Equation was supposed to do.

This page has the proper equations, but the practical take home message is that pH drops with increasing temperrature. In the case of water, this is caused by an increased dissociation of H
BTP v2.0.* Windows XP
User avatar
slothrob
Moderator
Moderator
 
Posts: 1768
Joined: Mon Apr 10, 2006 1:36 pm
Location: Greater Boston

Postby rrosa » Sat Jun 30, 2007 11:38 pm

Thanks. That page was really helpful, not so much to give any formula, but at least to explain the reason for the temperature dependence, which is probably very involved for a real mash.

So I decided to run a test, using the pH meter I bought last month. It just made me more confused. I diluted 450g of pilsner malt into 1.5L of very soft water (7ppm of bicarbonate, 1ppm of Ca, 0ppm of Mg, 0ppm Sulfate) at room temperature (70F here). With such negligible residual alkalinity I was hoping to decided between 5.7 (Palmer) and 5.8 (others), but I actually got a pH reading of 5.4! I realized that I am using pHep 4, which has an accuracy of 0.1pH, so this wouldn't be enough to decide between 5.7 and 5.8, but 5.4 was too low. I warmed up the mash to 140F (the maximum temp that pHep 4 can handle) and the pH went down to 5.2. I added 50g of Black malt (10%) and the pH went down to 5.0. I then added 5.2 Mash stabilizer and the pH oscillated a little between 5.2 and 5.3 and stabilized at 5.3. There is the 0.1 pH accuracy so that should be okay. It made me happy with the 5.2 stabilizer but I am still confused with the whole pH prediction thing.

Before you ask me about that, yes, I did calibrate the pH meter with the pH 7 and pH 4 solutions before doing the test. One thing that might have been a problem is that it was the first time I was using the Crankandstein 3D mill and it was quite dirty. The manual says to mill some malt just to clean the rolls and I used that very malt to do the test above. I am hoping that that was the problem and I should do the pH test again some other time. I will let you know the result then.
Ricardo - http://cervejarte.org/blog
MacBook 2GHz Intel Core 2 Duo 2Gb SDRAM running Mac OS X Snow Leopard 10.6.8
User avatar
rrosa
Pale Ale
Pale Ale
 
Posts: 55
Joined: Mon Jan 15, 2007 9:32 pm
Location: Rio de Janeiro

RA vs. Buffering

Postby slothrob » Mon Jul 02, 2007 10:01 am

Out of curiosity, do you know what the RA of your experiment's water was?
I get RA=5.6 and pH=5.8. It's interesting that this RA is actually high for the style (an all Pilsner Malt mash), which would usually call for an RA closer to -50.

The RA business is definately an approximation and not an exact science. One thing I've noticed, for example, is that there is no attempt made to adjust for the quantity of malt, which is what you're trying to neutralize with Calcium, in the first place.

Also, you might find better agreement in situations requiring water with more mineral content. The very soft water you describe has very little buffering capacity so that minor differences will have a profound effect on pH. Even in this situation, the one in your experiment, bringing the calcium up to the recommended 50-150 ppm range may give you more buffering capacity and stabilize your pH in the right range. I might try adding (in your 1.5 L) 0.3 g of CaCl2 and 0.05 - 0.1 g of CaCO3 (and maybe a pinch of MgSO4 for good measure) for an RA of around -25 to -35, a [Ca++] of ~100, and a [CO3] of ~25 to 50.

That doesn't follow the practice of many to use the softest water possible for a Pilsner, but it follows the RA rules and should result in a more buffered mash. The question is: Will it hit the pH 5.2-5.3 mark?

On a positive note, you did show the 0.4 pH unit drop from the raised temperrature, so you should have some reassurance that if you are in the 5.7-5.8 range cold, you'll hit close to 5.3-5.4 at mash temp. Of course, this is only useful if you have a directly fired mash tun, which I don't.
BTP v2.0.* Windows XP
User avatar
slothrob
Moderator
Moderator
 
Posts: 1768
Joined: Mon Apr 10, 2006 1:36 pm
Location: Greater Boston

Postby rrosa » Fri Jul 06, 2007 6:21 pm

I was hoping to do some more tests before writing again but I didn't have the time yet. I think the RA of the water I used was as low as you guessed, but I don't know it exactly. The pH was 6.0. You have a good point about the low buffering power with such low RA. I will do more tests with different types of water and with different salt additions. I will post the results when I'm done. Unfortunately (or not!), all types of water down here are either soft or very close to that.
Ricardo - http://cervejarte.org/blog
MacBook 2GHz Intel Core 2 Duo 2Gb SDRAM running Mac OS X Snow Leopard 10.6.8
User avatar
rrosa
Pale Ale
Pale Ale
 
Posts: 55
Joined: Mon Jan 15, 2007 9:32 pm
Location: Rio de Janeiro

Postby rrosa » Thu Aug 02, 2007 5:15 pm

I finally had some time to run some more tests. I took 510ml of four different bottled waters and the tap water and added 200g pilsner malt.

The pH of the water samples were

5.9, 6.4, 6.6, and 7.8,

all measured near 25C. Three of them were very soft (below 5 ppm of bicarbonate), one of them was not so soft (about 50ppm) and I don't know about the tap water.

After adding the malt, I got

5.5, 5.5, 5.5, 5.6, and 5.7.

I should remark that the pHep 4 has an accuracy of 0.1, but still the values seem off the predicted 5.7 value of Palmer and 5.8 of Ray Daniels for a zero alcalinity water (better approximated by the first three samples).

After increasing the temperature of the wort samples to 60C (the limit for the automatic temperature correction of the pHep meter) I got

5.3

in all of them.

In a sense this is in agreement with Palmer, which estimates a decrease of the pH
with the temperature to the value of 5.35 (assuming a decrease of .35 from his value of 5.7).

And just for fun, I added 10% carafa III (22g) and the pH dropped to 5.0. I then added a pinch of calcium carbonate and the pH went to 5.1. But there are just too many variables to do all the tests carefully, so I guess I will settle with this.
Ricardo - http://cervejarte.org/blog
MacBook 2GHz Intel Core 2 Duo 2Gb SDRAM running Mac OS X Snow Leopard 10.6.8
User avatar
rrosa
Pale Ale
Pale Ale
 
Posts: 55
Joined: Mon Jan 15, 2007 9:32 pm
Location: Rio de Janeiro

Water Chemistry

Postby slothrob » Fri Aug 03, 2007 9:15 am

Thanks for posting the results of your experiment. Very interesting.
I certainly wouldn't complain about pH 5.3
BTP v2.0.* Windows XP
User avatar
slothrob
Moderator
Moderator
 
Posts: 1768
Joined: Mon Apr 10, 2006 1:36 pm
Location: Greater Boston

Postby rrosa » Fri Aug 03, 2007 9:33 am

Good idea. The sparging should be more critical and this test you mention should indeed be interesting.
Ricardo - http://cervejarte.org/blog
MacBook 2GHz Intel Core 2 Duo 2Gb SDRAM running Mac OS X Snow Leopard 10.6.8
User avatar
rrosa
Pale Ale
Pale Ale
 
Posts: 55
Joined: Mon Jan 15, 2007 9:32 pm
Location: Rio de Janeiro

Calculating residual alkalinity

Postby lupulin5446 » Wed Jan 07, 2009 10:01 am

Residual Alkalinity =

+ Total Alkalinity (as ppm CaCO3) X (0.056)
- Calcium (as ppm Ca2+) X (0.04)
- Magnesium (as ppm Mg2+) X (0.033)

For example, Burton, and Munich have similar levels of alkalinity, but Munich has a much higher Residual Alkalinity.
The approximate levels of alkalinity in Burton and Munich are 236 and 253 respectively. Burton has approximately 263 ppm calcium, and 62 ppm magnesium. To calculate the RA, simply plug in the numbers. RA= (236) X (0.056) - (263) X (0.04) - (62) X (0.033) OR RA= (13.216) - (10.52) - (2.046) The RA for Burton is approximately .65

For Munich, the calcium is 76 ppm, and magnesium is 18 ppm. RA = (253) X (0.056) - (76) X (0.04) - (18) X (0.033) OR RA= (14.168) - (3.04) - (0.594) The Residual Alkalinity for Munich is approximately 10.534

To calculate the approximate wort pH of a 12P wort made from pale malt, use the formula: Wort pH = 5.59 + (0.028 X Residual Alkalinity)
Darker malts are more acidic, and will nuetralize water with a higher RA. Ideally, for a pale wort, the RA should be between 0 and -14.

If your mash is too alkaline, you can compensate for it by adding calcium salts, or food grade acids. These can be added to the wort, or directly to the mash, but note that alkaline water will leach more tannins during the sparge, so for some styles, it would be beneficial to sparge with less alkaline water. To adjust the pH by 0.1, add to the mash: 3g calcium sulphate, 2.5g calcium chloride, or .58g lactic acid PER kg of malt. When adding to the wort, use 2.5g, 2.1g, and .29g respectively.

To adjust calcium in the brewing water at room temperature, 260 mg(0.26g) calcium sulphate per Liter will add approximately 60 mg/L (ppm) of calcium. For calcium chloride, 220 mg per Liter will add approximately the same amount of calcium. For magnesium, 155 mg per Liter of magnesium sulphate will add roughly the same.

To increase the alkalinity, you can add 100 mg/L calcium carbonate (chalk), or 80 mg/L NaHCO3 (baking soda) to increase the alkalinity by 60ppm CaCO3. Keep in mind, that 100mg/L of chalk will also add 40ppm calcium.

This is an adaptation of information provided in a brewing course, it is not absolutely perfect, but it should suffice.
User avatar
lupulin5446
 
Posts: 2
Joined: Wed Jan 07, 2009 8:18 am


Return to BeerTools Pro General Topics

Who is online

Users browsing this forum: bernie879, Google Adsense [Bot] and 3 guests