So for the dense folks here (that would be me) the recommended chalk additions like promash give us to get proper water mineral levels will be off as some of the chalk will stay undissolved. I guess that's why some folks add it directly to the mash.
Adding chalk to the mash or to the water w/o dissolving it is the same.
(most) Spreadsheets and water calculators will calculate the amount of undissolved chalk necessary. This calculation seems to work until about 300-400 ppm chalk concentration and it assumes that chalk contributes only half its alkalinity potential. You can check that by entering 100 ppm chalk (0.1 g in 1 l water or 0.38 g in 1 gal water). The resulting alkalinity as CaCO3 (i.e. as chalk) will only be 49 or 50 depending on the used formula. Not 100 ppm as you would expect.
While this is not as intuitive as it should be, it seems to work when it comes to predicting mash pH through residual alkalinity.
If chalk is dissolved it does not have this odd behavior and it is also able to raise the mash pH more than just 0.2-0.3 pH units over the distilled water pH of the grist. I.e. the pH that you would get with very soft water.
OTOH, if I take a carbonator cap and add my chalk in the PET bottle, throw in some distilled and gas it, the stuff will go into solution?
I take it has nothing to do with the pressure, but rather the formation of carbonic acid in the water?
Presuming I shake the snot out of the PET bottle, how long will this process take?
Please straighten me out here, thanks.
I don't exactly know why dissolved chalk behaves so much different in brewing compared to undissolved chalk. If I test the alkalinity of a dissolved and a suspended chalk solution, of the same chalk concentration, I get the same alkalinity. I.e. the neutralizing power towards an acid is the same.
The dissolved CO2 will form carbonic acid which lowers the pH and converts the carbonate of the chalk to bicarbonate. That makes the chalk much more soluble. If the concentration of chalk that should be dissolved is fairly large, simple atmospheric CO2 pressure is not enough and you need to force carbonate the water. Do that by shaking. Then let it stand and you'll notice that the liquid starts to clear up. I still have to do some searching for a formula that gives me the minimum CO2 pressure that is needed to dissolve a given concentration of chalk.
If you want to give this a try, I'm glad to help. I also started to test my spreadsheet that allows for grist and water based mash pH prediction. I used it for the Doppelbock I brewed today and the prediction was only off by 0.01 pH units. Now that may have been luck, but for other beers in the past It has been off by less then 0.05 pH units which is the precision I was hoping for.