Is there a chemist in the house?

[Naich]

I'm currently delving into the murky water treatment waters. For starters I'm trying to understand residual alkalinity.

This page in "How to Brew" says the Kohlbach formula for calculating RA is to use the Calcium and Magnesium components in the water to calculate RA like this: RA = Alkalinity - ((Ca/3.5) + (Mg/7)) The units are mEq/l but this scales up to ppm/l.

But if you use the spreadsheet further down the page, the formula he actually uses is RA = Alkalinity - ((Ca/1.4) + (Mg/1.7)) - Cells K11 and L11.

I'm obviously missing something here, but I can't see what.

[Bobba]

I did hear on a brewing network podcast (this one I believe.. http://thebrewingnetwork.com/shows/719 ) that he updated the spreadsheet as it was incorrect before.
Perhaps that's why?

[Wolfy]

I'm currently delving into the murky water treatment waters. For starters I'm trying to understand residual alkalinity.

This document makes a great start to understanding water treatment, its one of the easiest and most logical to understand that I have ever read, it's focused on Melbourne water but I hope you still find it useful.

[Naich]

Thanks guys. The more I look into this the more confused I'm getting. I'm a bodger, not a chemist. I'm going to skim over this for now and come back to it later. It's little things like being told the residual alkalinity for a light beer should be around 25 on this board, while reading in How To Brew that the RA for a light beer should be around -50! It's beyond me.

[Bobba]

Thanks guys. The more I look into this the more confused I'm getting. I'm a bodger, not a chemist. I'm going to skim over this for now and come back to it later. It's little things like being told the residual alkalinity for a light beer should be around 25 on this board, while reading in How To Brew that the RA for a light beer should be around -50! It's beyond me.

Palmer always seems to make things more complicated than they need to be, which especially applies to water treatment. Choose something else to get you sorted on this topic. Graham's BYOBRA does a good job, although I remember reading that section about 5 times until it sunk in. Then the calculator on here makes it easy.

That link of yours Wolfy looks excellent, going to have a read over that now in fact

You're right about residual alkalinity - should be somewhere in the region of 20-25 (mg/L or ppm) for all but the darkest of worts

[Graham]

I am not convinced that the Kolbach stuff that Palmer relies upon actually works. The theory is based upon an obscure 1950s paper that seems to have died a death shortly afterwards. I have never seen the Kolbach residual alkalinity idea cited in modern commercial brewing literature. I have played with the Kolbach theory, plugging in numbers from water compositions that are known to give proper mash pH, and the results predict a mash pH that is way too high.

The colour method of choosing an appropriate water composition is fraught with error. Roast malts do not supply consistent acidity per unit colour. The most acidic malts per unit colour are the stewed malts, like crystal or Munich. In contrast chocolate and black malts contribute hardly any acidity when used in normal quantities. You could produce a jet-black beer using black malt and it will not lower the pH at all.

Also, there are buffering effects that go on within the wort. None of these are taken into account with either Kolbach or Palmer, and they assume that the effect is linear. The reactions are far from linear. It would be too difficult to take the buffering effects into account anyway, but because of this it makes it practically impossible for people at our level to reliably predict mash pH.

In the end we use a 'suck-it-and-see' approach: get it close at the first attempt, and then alter the levels next time round if the results are not close enough.

[Naich]

Thanks for the info Graham. I'll definitely not be delving too deeply into it at the moment, as it doesn't seem to be a precise science anyway. I'll take Bobba's advice and read your book again

[InsideEdge]

It also doesnt help that ph papers are terrible at giving accurate results. I read somewhere that they have been shown to have a systematic error of reading 0.3 too low.

Having said that I really like this water treatment calculator http://www.ezwatercalculator.com/ you just plug in your water, beer colour, any salt additions and it gives you your end water profile, estimated ph compared to the recommended ranges in palmer. You can manually alter the spreadsheet also to suit your needs if you wish.

[Gadders]

Hey,

I recently went through the whole RA thing with water treatment aswell. At the end of it I decided to try this insted of relying on spreadsheets; the nite before I have a brew I make a 200g grist of the brew Im going to make eg 94% pale, 5% crystal 1% wheat etc and treat 500ml of water to my spec. Heat to strike temp, mix and leave it for 15/20 min then take a couple of p.H readings, if its in the p.H is around the 5.2 ball park and my water has around 150ppm Calcium then the brew is on. I not sure if this is oversimplified but it seam to work well for me.
Of course Graham's water treatment calc is useful for working out how much of each salts to add water calc
Cheers

[WallyBrew]

I'm currently delving into the murky water treatment waters. For starters I'm trying to understand residual alkalinity.

This page in "How to Brew" says the Kohlbach formula for calculating RA is to use the Calcium and Magnesium components in the water to calculate RA like this: RA = Alkalinity - ((Ca/3.5) + (Mg/7)) The units are mEq/l but this scales up to ppm/l.

But if you use the spreadsheet further down the page, the formula he actually uses is RA = Alkalinity - ((Ca/1.4) + (Mg/1.7)) - Cells K11 and L11.

I'm obviously missing something here, but I can't see what.

In answer to your question you are not missing anything and both of the formulae are correct.

In the original Kolbach formula RA = Alk - (Ca/3.5) - (Mg/3.5)
all parameters must be in the same units and these could be as calcium carbonate, milliequivalents or calcium oxide as Kolbach would have used.

In the second formula RA = Alk - (Ca/1.4) - (Mg/1.7) the RA will be as calcium carbonate, the total alkalinity as calcium carbonate, the calcium as calcium and the magnesium as magnesium.

Alk is the total alkaliity

If we take values for inner London water (supplied to many millions and not that dissimilar to Cambridge water) then the values to be used in the formulae are:

Total alkalinity as calcium carbonate 210
Calcium as calcium 102
Magnesium as magnesium 5
Calcium as calcium carbonate 255
Magnesium as calcium carbonate 20.8

1st formula RA = 210 - (255/3.5) - (20.8/7)
RA = 134

2nd formula RA = 210 - (102/1.4) - (5/1.7)
RA = 134

The result tells you that the pH of the final wort (of about 1048) will be 0.23 higher than a mash made with distilled water. Reduction of the alkalinity to 75 should give a pH that is the same as a distilled water mash. All you now need to know is what the pH of your chosen mash schedule would be if made with distilled water.

Please be aware that Kolbach was doing this work in order to help those who have/had to work within the German beer purity laws.

He appears to have made no claim that any given pH could be achieved because he accepted that many other factors come into play and therefore this work should be utilised for what it is - a starting point toward achieving an ideal pH.

[Naich]

Thanks for that. That is clearer, but I've a couple of questions. Please feel free to tell me to go and read a chemistry book if these are really stupid questions, by the way

Question 1: When you say "Magnesium as calcium carbonate", my question is "do what"? Does "as" mean "the equivalent of", being some sort of chemistry thing where you can express one chemical in terms of another? Is this effectively the same as changing the units based on the relative molecular weights, or something along those lines?

2. In a water report, is "Calcium" a separate chemical in the water to the calcium that is tied up in calcium carbonate?

3. Given that there is not a precise method of calculating mash pH and Graham has done experiments that throw doubt onto the entire subject, is it worth even accounting for the calcium and magnesium components of the water in a calculator? Would it be just as valid to simply pick a desired RA (say 25 for light beers, as most people do here) and simply use CRS to adjust the measured alkalinity to this level, regardless of Ca and Mg levels in the water? Would people with differing Ca and Mg levels actually end up with different mash pHs?

4. This is a long shot, but if the answers to questions in 3 are "no, yes, possibly", then might the discrepancy between Palmer's desired RA level of -60 Vs. JBK typical desired RA of 25 be the result of the average Ca/Mg components of people's water (not taken into account in the JBK calculations) effectively dropping the RA of JBK people's water by 85 to make the end result the same?

Put in a possibly clearer way: Palmer wants a RA of -60, which seems at odds with JBK's desired RA of 25. However, Palmler's calculator reduces the RA of the water with the Kolbach equation. This is not done by JBK people, so their desired RA is higher. Averaged out, the Ca and Mg levels in JBK people's water have the effect of reducing RA by 85ppm CaCO3. So JBK people are taking Ca/Mg effects into account but using a fixed, averaged value for them.

Or am I just talking bollocks again?

[WallyBrew]

Question 1: When you say "Magnesium as calcium carbonate", my question is "do what"? Does "as" mean "the equivalent of", being some sort of chemistry thing where you can express one chemical in terms of another? Is this effectively the same as changing the units based on the relative molecular weights, or something along those lines?

Yes. You divide the quantity of magnesium by 24, its atomic mass and multiply it by 100 the molecular mass of calcium carbonate.

2. In a water report, is "Calcium" a separate chemical in the water to the calcium that is tied up in calcium carbonate?

No. The calcium shown on a water report is the total amount of calcium present in the water. In terms of what the composition of a water is it is worked out from the figures of analysis by combining the cations K, Na, Ca, Mg in that order with the anions Cl, NO3, SO4, HCO3 in that order. So you would start with KCl then NaCl until you get to CaCO3 and finally MgCO3. So as you can see not all of the alkalinity is derived from calcium.

3. Given that there is not a precise method of calculating mash pH and Graham has done experiments that throw doubt onto the entire subject, is it worth even accounting for the calcium and magnesium components of the water in a calculator? Would it be just as valid to simply pick a desired RA (say 25 for light beers, as most people do here) and simply use CRS to adjust the measured alkalinity to this level, regardless of Ca and Mg levels in the water? Would people with differing Ca and Mg levels actually end up with different mash pHs?

4. This is a long shot, but if the answers to questions in 3 are "no, yes, possibly", then might the discrepancy between Palmer's desired RA level of -60 Vs. JBK typical desired RA of 25 be the result of the average Ca/Mg components of people's water (not taken into account in the JBK calculations) effectively dropping the RA of JBK people's water by 85 to make the end result the same?

Put in a possibly clearer way: Palmer wants a RA of -60, which seems at odds with JBK's desired RA of 25. However, Palmler's calculator reduces the RA of the water with the Kolbach equation. This is not done by JBK people, so their desired RA is higher. Averaged out, the Ca and Mg levels in JBK people's water have the effect of reducing RA by 85ppm CaCO3. So JBK people are taking Ca/Mg effects into account but using a fixed, averaged value for them.

Or am I just talking bollocks again?

The RA from the Kolbach equation is not the same as the JBK RA

The Kolbach equation works out how much of the alkalinity in the water will be neutralised by the calcium and magnesium during mashing. Referring back to the London mains water the result of (255/3.5) - (20.8/7) is 76.
This figure is the equilibrated alkalinity. So of the 210mg/L of alkalinity 76 will be neutralised by the calcium and magnesium. If one mashed with this as it is then the 134mg/L of alkalinity that has not been utilised will drive the pH toward the alkaline end.

If the 210mg/L of alkalinity were to be reduced to 25 by addition of acid then putting the figures into the equation - RA = 25 - (255/3.5) - (20.8/7) we get a negative result -51. This negative result indicates that there is no alkalinity to drive the pH toward the alkaline end, in fact, the reverse should happen and the pH should be driven toward the acid end.

If the RA could be brought down to 0 then the pH of a mash with that water should be the same as one made with distilled water. For this same water this can either be done by using sufficient acid to neutralise the 134mg/L of RA or by adding calcium sulphate at a rate of around 800mg/L.

Going to your first link "How to Brew"

Determining Calcium Additions to Lower the Mash pH
But what if you want to brew a much paler beer, like a Pilsener or a Helles? Then you will need to add more calcium to balance the alkalinity that your malt selection cannot.

1. Go back to the nomograph and pick a point on the RA scale that is within the desired color range. In this example, I picked an RA value of -50.

You will see that the RA quoted is negative and can be seen as so on the nomograph. Note that this value is in agreement with the RA of London water when reduced to 25mg/L of alkalinity.


Yes it is worth knowing your calcium but not necessarily your magnesium as calcium is required during the brewing process typically 50 to 150mg/L

[Naich]

Excellent - I think I've got it now. Thank you very much for taking the time to post that. It is much appreciated.