ajdelange

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Unsurprisingly enough the beer will taste 'chalky' (or so I've been told). The situation is similar to what a home brewer gets when he follows one of those spreadsheets or calculators that tells him that the color of his beer requires that he add 2 tbsp chalk to a 5 gal mash. The chalk begins to dissolve and the pH rises slowly and so the brewer think all is fine but the long after he has put the pH meter away the chalk keeps dissolving. If he is lucky it gets trapped on the grain bed when he lauters/sparges. If he isn't it carries over into the kettle and fermenter where it continues to dissolve. All this results in higher pH which means more bicarbonate in solution and that must be responsible for the 'chalky' taste (Gordon Strong describes it as "AlkaSelzer beer").

Kaiser

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I don’t think it’s a good idea to skip decanting the water. Yes, only part of the chalk is expected to re-dissolve during mashing. you can test its effect on mash pH by playing around with the “decant water” check box in the water calc link that I posted last. But make sure you remove the additional chalk that I added simply as a process aid.

W/o decanting the mash pH will not be as high as it would be w/o any CaCO3 precipitation but also not as low as it could be. So I would not skip that step.

A.J do you have practical observations to support this? I know we do have a disagreement on this and your understanding of the underlying chemistry is greater than mine. But I argue that what you are describing is not happening in most cases. I understand that if the chalk doesn’t fully dissolve it may end up in the BK or even the fermenter. But I have not seen evidence in in this. In fact there is one well documented experiment where I used dissolved and undissolved chalk (http://braukaiser.com/blog/blog/2009/11/24/undissolved-vs-dissolved-chalk-in-the-brewing-water/) and I did not see that pH difference in the fermenter.

Yes, there are bicarbonates in beer. If you have 2 atm CO2 pressure and a pH of 4.5 you need about 60 ppm HCO3 for equilibrium. But those 60 ppm are only a function of the CO2 content and the pH and not the original brewing water.

I agree that chalk can have a negative impact on beer taste but I don’t thinks it happens via that way you described it and maybe we can discuss this.

Kai

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ajdelange

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The 'observation' that it will taste chalky is not mine but rather what I have been told by people who have put lots of chalk into beer and, of course, Gordon's statements about alka selzer which is in his book and which he has mentioned in a couple of talks he has given. The rest is my attempt to explain why this might happen. If you have chalk in an acidic medium it is going to dissolve. Mash and wort contain a fair amount of acid. At pH 5.5 88% of the carbo will be in the form of CO2. In hot mash or the kettle CO2 isn't very soluble so a lot of that gas will escape. If gas escapes then the balance between carbonic, bicarbonate and carbonate is upset and can only be restored if more carbo is supplied by the system or the pH goes up. Both of these happen but the mash is a buffer so that the pH doesn't change that much but it does change some and will continue to do so until the system comes to equilibrium with atmospheric CO2 which will never happen until the pH reaches the vicinity of 8.4.

I would really expect most of the undissolved chalk to be trapped in the filter bed. Certainly if you are withdrawing bright wort that should be the case. So that leaves the time in the mash tun which is usually an hour for ales but could be several hours in a decoction mash. CaCO3 seems to react slowly and so even does bicarbonate as I was surprised to discover when I recorded pH continuously during an alkalinity titration (http://www.wetnewf.org/pdfs/measuring-alkalinity.html). So perhaps that's what is preventing much from dissolving. Or perhaps, even if some extra dissolves the yeast, which strive to maintain a pH they like, simply put more effort into secreting the acids they need in order to overcome the additional buffering imposed by the dissolved chalk (which in itself should be an argument for getting or keeping the chalk out).

But if the chalk isn't dissolving, how do we explain the chalky taste?

Good point. I get 72 ppm for the bicarb content at 2 Atm and pH 4.5 (I get about the same number as you do if I use ideally dilute chemistry). But if I increase the pH to 4.7 the bicarb zooms to 115 i.e. about doubles. Base purely on my line of reasoning I would suggest that the stress of the extra alkalinity would result in a higher pH for the beer but that's essentially saying that the yeast are unable to handle the extra alkalinity and I don't know that. The usual reason for controlling water alkalinity is for the benefit of the enzymes in the mash tun. I certainly have no experimental data correlating start and finish fermentation pH's for unusually alkaline worts.

Let's assume that more calcium carbonate is dissolving (I think that part has to be true if enough time is involved) and that this appears in the fermenter and that the yeast can handle the extra buffering load. That leaves the calcium as a possible explanation. Perhaps Gordon's "AlkaSelzer" is more apt than "chalky". Perhaps the guys (I think of my LHBS operator in particular) that use that phrase are victims of confirmation bias "I used chalk and the beer tastes chalky." But then any beer loaded with calcium and bicarbonate would taste like AlkaSelzer and I guess they do.


I'm not going to pound my fist on the table and declare my explanation gospel. There certainly are questions

Kaiser

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I agree. I don’t see my words as the gospel either and I we do seem to agree on a number of points.

I don’t contest the observations that Gordon or others are making. It would be interesting to have more data on these beers, though. For example the amount of chalk that has been used. Until a few years ago people were using John’s spreadsheet which called for a high amount of RA for dark beers. That RA was generally supplied by lots of chalk. More chalk than what you get out of modern water calculators.

I’m in agreement with you that if undissolved chalks makes it through the BK into the beer you may not see an impact on beer pH simply b/c the yeast is working on keeping that pH low. As a result you could end up with excessive calcium. So an interesting experiment would be the creation of carbonated waters with a pH of 4.5 and varying amounts of calcium. Then taste these waters to see if you end up with that “chalky” taste.

This would be particularly interesting for BIAB brewers where the run-off is naturally cloudy and the undissolved chalk can end up in the BK.

My point is that the bicarbonate content of beer is controlled by its carbonation level, pH and temperature. It is not controlled by water treatment unless that alters your beer pH. beer pH is easy to measure and its very likely that the “chalky” beers didn’t have a higher pH than normal tasting beers. Thus the bicarbonate content of the beer would not be the culprit.

yes, I can support that theory. I.e. the chalky taste is from excessive calcium and not bicarbonate.

But again, how much chalk to you have to add to get into the danger zone and how big of a role does cloudy wort run-off play.

Kai

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Kaiser

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I just noticed this when looking at Bru'n water: It is illegal to keep separate copies of that spreadsheet. Your copyright clearly states that :"Reproduction in whole or in part in any form or medium without the express permission of Martin Bungard is prohibited"

You may want to clear up that copyright in order to resolve some legal issues with keeping multiple copies or even downloading it.

Kai

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Hermit

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He'd have a pretty hard time making a case stick considering he has it available for download and his posts here, but, yeah making the copyright wording match the actions is probably a "Good Thing"(tm)

nobeerinheaven

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One additional question: Why doesn't chalk precipitate out of the beer with the hot break? (I assume that it's because of the lower PH of the wort, but this post suggests that the elimination of CO2 is really what drives the precipitation of chalk, and that would happen with wort too as its boiling, right?)

Kaiser

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chalk does not precipitate during the boil b/c of the lower pH. Even if CO2 is driven off, there are enough acids in the wort to keep the pH in the low to mid 5s and at that pH there is hardly any carbonate present.

Kai

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mabrungard

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As Kai said, additional chalk precipitation would not be occurring in the boil. The low pH and the rolling action of the boil would tend to help any suspended chalk and that action can be counterproductive for kettle pH. The slow reaction of chalk and its dissolution means that if there is excess suspended chalk in the kettle wort, the kettle pH may rise a bit higher than desired during the course of the boil. Hopefully any suspended chalk would settle in the post-boil stand in the kettle, but that is doubtful since its relatively short and the suspended chalk has very small particle size. The effect may be that chalk's pH elevating contributions continue into the fermenter. That is not a good thing either.

The bottom line is that suspended chalk is a poor alkalinity producer and cannot be relied upon for brewing use. I just revisited Kai's excellent paper: "The effect of brewing water and grist composition on the pH of the mash" where he presents experiments on suspended chalk and mash pH. It showed that chalk is quite ineffective at moving mash pH and aside from an initial bump of about 0.1 unit, it makes little difference when additional chalk is added to the mash. That agrees with the results that my professional and homebrew clients have reported to me. Do yourself a favor and don't use chalk in brewing.

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