Calcium Carbonate (Chalk) has little use in homebrewing

Gavin C · Mar 20, 2015

Calcium Carbonate seems to appear in water adjustment tools. However I have recently learned that it takes days to react and is entirely unsuitable as a water adjunct for the purposes of home brewing.

I used it on 1 batch. Added to strike water. Result=Cloudy strike water.

Just want to share this important tit-bit and thank @AJDelange for the education.

mabrungard · Mar 20, 2015

Yep! Although there are cautions in Bru'n Water against using chalk, I should probably make the program pop up a big red warning if anyone inputs chalk in the program.

You can use chalk, but unless you are dissolving it under high CO2 pressure to make a chalk solution, its otherwise useless in brewing water chemistry.

Use caution, my friends.

grrickar · Mar 20, 2015

I use dry erase markers instead. Adds some color and less dust too! :cross:

ajdelange · Mar 20, 2015

There is one application in brewing where you must use chalk and that is where you are trying to emulate natural water. In mesic regions most ground water contains calcium bicarbonate which arises from limestone dissolved by carbonic acid derived from the respirations of subterranean bacteria. To closely match the ions profiles of such waters you must dissolve limestone with carbonic acid. As the subterranean partial pressure of CO2 is orders of magnitude higher than in the atmosphere you must use higher partial pressure of CO2 as well. One atmosphere is sufficient but if you go higher you may be able to get the chalk to dissolve faster. At one atmosphere it can take a long time but just bubbling CO2 through a suspension in a closely covered container will eventually get the job done.

When you are finished you have the requisite Ca(HCO3)2 solution which may well be supersaturated WRT CO2 and CaCO3 in which case both will leave solution again. This will certainly happen when the water is heated in the HLT. This would, of course, happen to the brewer who used the water you are trying to emulate. If just heating doesn't drop sufficient bicarbonate the brewer will take other steps to rid himself of it. So why not save yourself the trouble and just skip this part of the excercise?

Hermit · Mar 30, 2015

If you were to simply add it to your water and have some sort of stir mechanism would the CO2 in the air eventually get the job done? This is something I planned on trying before I took a 6 month contract job that kept me from all brewing activities. I might try it in the near future.

ajdelange · Mar 30, 2015

Yes it would to a certain extent. Chalk and CO2 would dissolve until the alkalinity and hardness both reached about 50 ppm as CaCO3 at which point the pH would be about 8.3. At that point no further CO2 or chalk would dissolve. The undissolved chalk, the carbonate, bicarbonate and carbonic acid and the wee bit of CO2 in the air are all in equilibrium with one another under these conditions. To get more chalk to dissolve increase the partial pressure of CO2. There is a chart at http://www.wetnewf.org/pdfs/co2-equilibrium.html