Author Topic: question on water chemistry, reducing pH, and knowing when to give in  (Read 1183 times)

Offline pikelakehomebrew

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Edit: I am pretty sure that my estimation of the Biocarbonates (HCO3 or CaCO3) has got to be off.  But I still want to double-check with the community and see if my math is at least on.


Got your math nerd hat on?   ;)  Good.

So I'm delving deeper into the math and science behind brewing — much in part to the book "Designing Great Beers" by Ray Daniels — and I'm presently wrapping my head around water chemistry (or trying to anyway) but ran into a red flag when I was evaluating just how much Calcium I would need to bring the levels down to earth.  It seemed pretty extreme, so I thought I would confer with the chemistry and math geeks here and make sure my calculations were correct, and if they are, how I can bring the pH level down without introducing off flavors like chlorine, salt, etc.

Water profile
For starters, I checked with my city water source and they were able to provide the general pH range (7.5-8.1), the Calcium reading (170 ppm), and Magnesium reading (28 ppm), but did not have any readings for Biocarbonates.  So based upon the formula that Daniels provided:

Code: [Select]
pH = (0.028 x [(Biocarbonate ppm x 0.056) - (Calcium ppm x 0.04) - (Magnesium ppm x 0.033)] )
I guestimated (based upon reverse-engineering the formula) that our Biocarbonate reading must be in the ballpark of 4921 ppm, so the end formula would have these values:

Code: [Select]
7.5pH = (0.028 x [(4921 ppm x 0.056) - (170 ppm x 0.04) - (28 ppm x 0.033)])
Achieving 5.5 pH

So I took the same formula, but factored in 5.5 as the pH rating, kept the Biocarbonates and the Magnesium at the same value (assuming that those two would remain constant), and then figured out how much Calcium it would take to bring the pH level down to 5.5.  That formula is:

Code: [Select]
5.5pH = (0.028 x [(4921 ppm Biocarbonates x 0.056) - (1956 ppm Calcium x 0.04) - (28 ppm Magnesium x 0.033)] )
And the difference of ppm of Calcium between a pH level of 7.5 and 5.5 comes out to be about 1786 ppm of Calcium — and because Calcium is only 27% of Calcium Chloride, it would take 6615 ppm of Calcium Chloride to  reduce the pH to 5.5.  And if I have my percentages right, that would also mean adding over 3100 ppm of Chloride.

Translate that into ten gallons of strike and sparge water as an example, that would be nearly nine ounces of Calcium Chloride to bring the pH down.

If I'm not mistaken (and I probably am — I am a man, a home brewer, and am prone to err), that much Calcium Chloride could have a pretty bad effect on the flavor of the water, the mash and in turn, the beer.

Do my figures look correct in terms of the correction of pH levels?  Or is it possible that my Biocarbonates guestimation is off altogether and is by far too high?  Since the city doesn't measure CaCO3, I'm stuck trying to guestimate that without sending my water in for a professional reading.

I've no real interest in answers like "just go get some distilled water" — simply put, I don't learn anything from copping out and grabbing distilled water off the shelf.  Part of this exercise is to learn some facets of the chemistry of water and how I can correct it as a home brewer (within reason).

And just to be clear, my beers don't taste bad at all — I can't say that having a higher mash pH (of about 6.3 or so, which is what I've been averaging) has had a dramatic effect on my beer.  But I am trying to really dial it down and improve my mastery of water chemistry.

Thanks in advance.
« Last Edit: November 14, 2012, 09:29:56 PM by pikelakehomebrew »
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Offline tschmidlin

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Re: question on water chemistry, reducing pH, and knowing when to give in
« Reply #1 on: November 15, 2012, 02:22:41 AM »
You don't have 4921 ppm of bicarbonate.  I'm not a water expert, but I don't need to look that one up.

When I plug what few numbers we have into Bru'n water, I can balance your water with 650 ppm of bicarbonate.

I don't know if that formula is accurate or where Ray got it.  I also don't know if you can use it the way you are trying to.  I would skip it.

I agree you shouldn't just get some distilled water, it is better to make an informed decision.  Someone with more water knowledge than I will weigh in on this, but to me it is worth the $16.50 to send a sample off to Warb labs and have the water analyzed.  If your beers taste fine then I wouldn't worry about it, although the pH of 6.3 makes me skeptical - I believe either the beer is good and your pH is lower than you are measuring, or the pH is accurate and your assessment of your beer is not. ;)

http://www.wardlab.com/FeeSchedule/WaterAnalysis.aspx
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Offline davidgzach

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Re: question on water chemistry, reducing pH, and knowing when to give in
« Reply #2 on: November 15, 2012, 05:35:16 AM »
I would go back to your city water authority and ask for a full water report.  IME you have to talk to someone in the lab.  If you did and that is all you got, then disregard.

Dave
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Offline narvin

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Re: question on water chemistry, reducing pH, and knowing when to give in
« Reply #3 on: November 15, 2012, 06:11:45 AM »
Your math may be right, but I don't think the science is correct  :).  Water chemistry, alkalinity, and pH are a complicated subject. 

The math you're using looks like Kolbach's equation which estimates the pH shift in the mash based on alkalinity in the water and the reactions from calcium and magnesium with phytin in the malt.  Obviously, this is not going to hold in plain water.  As Tom said, you can make a rough estimate of alkalinty based on your other ion counts and some assumptions, but a full water report is really the way to go.

What you care about as a brewer is the pH of the mash, which depends mostly on the alkalinity (buffering capacity) of the source water, the water mineral content, and your grains in the mash.  Start by getting a full water report.  Your city water lab can usually help, but remember that these numbers will be averages and may not actually represent your current water (or even a water that can physically exist).  Make sure your measurements are correct.  A pH of 6.3 for the mash sounds pretty high... if you're using those economy strips, at least buy the more expensive ColorPhast test strips.  And, download a spreadsheet likw Kaiser's water calculator or Bruin Water and start playing around with it.  If it interests you, you can start to look at the math once you understand how it is applied.
« Last Edit: November 15, 2012, 06:13:42 AM by narvin »
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Offline hopfenundmalz

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Re: question on water chemistry, reducing pH, and knowing when to give in
« Reply #4 on: November 15, 2012, 06:25:57 AM »
I think Narvin has it summed up. Martin might have more insight for us if he responds.

In the meantime, read this section of Brunwater and see if it has any information for this case.
https://sites.google.com/site/brunwater/water-knowledge
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Offline pikelakehomebrew

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Re: question on water chemistry, reducing pH, and knowing when to give in
« Reply #5 on: November 15, 2012, 07:09:48 AM »
The gig's in... I got a fragment of the water report (I think our city water guy felt like I didn't want/need the whole report), and the CaCO3 levels are MUCH MUCH lower than I guesstimated, to the tune of 270 mg/L.  I figured the water chemistry was far too complex to just flip a formula upside down to figure out the CaCO3 levels based upon the pH, Ca, and Mg values.

I'll re-assess my findings with the new data if I have a chance later today and re-ping the forums.
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Offline Kaiser

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Re: question on water chemistry, reducing pH, and knowing when to give in
« Reply #6 on: November 15, 2012, 07:55:41 AM »
You guys are correct. There is no correlation between Calcium, Magnesium, bicarbonate and the water pH. There is a correlation for mashes. part of this correlation is residual alkalinity, which is a water parameter that has been defined by brewers. I.e. you won't find this on a water analysis.

The formula in Ray's books is fairly outdated. I think it stems from a misinterpretation of Kolbach's work on brewing water composition and pH. He cared about cast out wort pH while many thought he was talking about mash pH.

Getting a water report from Ward Labs is the best approach to understanding your water. Water departments are not obligated to report all the ions that we brewers care about. If you are only interested in an estimate of the residual alkalinity but know general hardness (calcium and magnesium hardness) and alkalinity you can estimate residual alkalinity as

residual alkalinity = alkalinity - general hardness / 4

Hardness or general hardness is sometimes given on water reports b/c it determines how much detergent you have to add to laundry.

I do have a lot of water articles here: http://braukaiser.com/wiki/index.php?title=Main_Page#Ingedients

Kai
« Last Edit: November 15, 2012, 07:57:32 AM by Kaiser »

Offline a10t2

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Re: question on water chemistry, reducing pH, and knowing when to give in
« Reply #7 on: November 15, 2012, 09:39:00 AM »
the CaCO3 levels are MUCH MUCH lower than I guesstimated, to the tune of 270 mg/L.

FYI, there are a lot of things that can be reported as CaCO3 equivalent.
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