Question about small chalk addition

Summary: Is a small amount of chalk effective or am I just adding insoluble minerals to my mash?

Long form:
So I am in need of a light pale ale for Summer. Here is the malt bill:

9lb Breiss pilsen (1 SRM)
1.5 Weyerman Carahell (roughly 11 srm)
Various late addition hops.
S-05 yeasty beasties

I do BIAB and will mash the grains with 7.75gal water.

I normally use gypsum and calcium chloride in the mash to boost calcium and set the sulfate to chloride ratio along with baking soda (to boost the 'OH's and lactic to (hopefully) arrive at the pH predicted by Ez Water Calc. and Bru'n Water Calc. It has worked well so far, the beers have been decent.

I'd like to move away from baking soda so i am looking at chalk as a way to build some bicarbonate/alkalinity along with calcium. Respected contributors have repeatedly stated that chalk doesn't dissolve well in the mash. I am wondering if that is true even if you only use a small amount of chalk.

The image below shows my planned water additions and expected profile based on the "yellow balanced" profile in Bru'n water. Ez Water Calc is also agrees that this combination would produce a proper pH. But will the chalk dissolve in the mash? Or am I just adding insoluble minerals to my mash?

Pic below:

Chalk is ineffective. I have even seen experimental data that shows a decrease in mash pH when chalk is added. There are 3 things at work:
1. Chalk is insoluble
2. Even in an acid pH environment it dissolves very slowly. To get it to dissolve rapidly the pH must be much lower than mash pH.
3. When it does dissolve if you are in the mash the calcium released will react with the phosphate from the malt to produce protons (acid).

Number 3 suggests, based on the stoichiometry of a mash saturated WRT apatite, that the effective alkalinity will be 30% of the alkalinity of the carbonate ions in the chalk. Experiment in adding chalk to malt shows little or no effect or even the decrease in pH. This means that protons are being released by the calcium reaction faster than the bicarbonate can suck them up.

My read on chalk at this point is that it is unpredictable. What I am saying is that I don't know how to put these three factors together to predict the effect of a chalk addition. It depends on too many things.

AJ did some bang up work on chalk and lime for the Water book. You should look forward to seeing that in print this year. Not surprisingly, he found that chalk was not very effective.

What was surprising was that there is the spector of impure lime supply out there. There is lime that either has impurities in it, was not fully converted to Ca(OH)2, or has partially degraded to chalk. In any case, there is the possibility that you won't always get the amount of alkalinity you expect when adding lime. That is a little troubling, but is always correctable with a pH reading and a little more lime added. At least you don't have to worry about overdosing (as long as you calculate and measure correctly).

One of the realizations that I came to in helping with the Water book (I think AJ did too) was that baking soda may not be a bad component for adding alkalinity. The caveat is that the starting water needs to have low sodium. Low sodium is typically a safe assumption since the water apparently has low alkalinity (and probably low TDS). Since you only add baking soda to the mash and not the sparging water, the overall sodium content of the finished wort does not really go up that much since its diluted by the low-Na sparging water. Right now, Bru'n Water does not take into account the 'dilution' of sodium in the overall water due to the sparging water component. I'll work on that someday. But the bottom line is that if you aimed for a modest Na limit of say 40 ppm, you can get a decent amount of alkalinity added to the mashing water. It might be enough for many beers.

Now back to the beer at hand. That 1.5 lb crystal dose is a fairly decent percentage, so I guess its possible that the alkalinity is needed. But I would normally expect that little to no alkalinity is needed for a pale beer like that. One thing you are doing is simultaneously adding alkalinity and acid to the mash. They counteract each other, so there is probably no need for the baking soda. Take out that mineral and dial back the acid to see if the pH prediction meets your goal.

The Yellow Balanced profile should be OK for a hop focused beer. I would shy away from it if aiming for a maltier style.

Thanks for the thoughtful responses.

Regarding baking soda, i am aware of the sodium addition, so I limit its use to a max of 0.2 grans per batch. That keeps sodium low but does add hydroxide. Thats the right word isn't it?

I understand that adding the acid negates the base and i'll follow up on your suggestion. I can add a bit more Calcium Chloride and gypsum to replace the calcium i thought the chalk would provide. Thanks again!

nutty_gnome said:

That keeps sodium low but does add hydroxide. Thats the right word isn't it?

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No it isn't. Bicarbonate adds alkalinity (I think that's the word you are looking for) but does so in the form of the bicarbonate ion. The term alkalinity refers to the proton (hydrogen ion) absorbing property of a substance. Bicarbonate has alkalinity because it absorbs protons and in so doing becomes carbonic acid: HCO3- + H+ ---> H2CO3.

Hydroxyl ions are alkaline because they absorb protons becoming water in the process: (OH)- + H+ ---> H2O.

At normal mash pH, however, hydroxyl ions are few. At pH < 7 there are less than 0.0000001 moles of (OH-) per liter of solution.

mabrungard said:

There is lime that either has impurities in it, was not fully converted to Ca(OH)2, or has partially degraded to chalk.

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There is a very simple test for chalk in lime, from whatever source. By 'incomplete conversion' Martin refers to the fact that lime is made from chalk (limestone) by roasting it.

Put some of the lime into a glass and drop a little vinegar on to the powder. If it fizzes a wee bit there is some calcium carbonate in it. If it fizzes vigorously there is a lot and it should probably be discarded.