bicarbonate question.

From by understanding if you boil water calcium bicarbonate is precipitated out. Now if you have somewhat soft water and boil a pot of water you will see it along the side of the pot. Can you scrape that off, save it and use that later to add alkalinity if brewing a dark beer?

The deposits on the side of the kettle will represent mostly the calcium carbonate content of the water. There might be other minor ions in those solids, but not enough to worry about. That chalk deposit will suffer the same difficulty in resolubilizing into solution if it were added back to water. The dissolution of chalk into water is a very time intensive process and it doesn't happen very quickly. You are still better off using pickling lime to neutralize excessive grist acidity.

I was referring to adding the homemade chalk to mash as you would with store bought chalk to balance the pH. Would it be as efficient or effective?

If you boil water and it turns milky as boiling is approached that is mostly calcium carbonate referred to as 'precipitated chalk'. If you heat/boil softer water and it does not turn milky the residue on the side of the vessel does not contain only calcium carbonate but sodium sulfate, magnesium chloride.... In the first case the precipitated chalk is perhaps not as pure as what you would buy from a chemical supply house but should serve just as well as a mineral addition.

That's what I was looking for, thank you. My water does turn milky white right before it is boiling so it is calcium carbonate. I know it is not as pure but I often like to try to see how brewers back in history would use what's available to make things work. It's seems like this might have been an option. I might give this a try one day.

blacksailj said:

I was referring to adding the homemade chalk to mash as you would with store bought chalk to balance the pH. Would it be as efficient or effective?

Click to expand...

That's actually what he was addressing. The stuff you buy at the store doesn't dissolve well at all either. It's the same stuff. Just because you get it at the store doesn't mean it will work as well as it could.

Just grabbed a few solubility products from Wikipedia. (under standard conditions but they act similar as far as brewing is concerned)

Ksp of:
Calcium Hydroxide (Pickling lime): 4.68×10^−6
Calcium Carbonate (Chalk): 4.8×10^−9


Pickling lime is much... much... much more soluble than chalk. As in 1000x more.

That's interesting. Never would have thought of that, I plan on looking into it. I've been reading as much as I can on water chemistry and the different cause & effects. It's a lot to take in but making progress. Fourms like this help a lot because there are many brewers with knowledge of all sorts.

The solubilities of both CaCO3 and Ca(OH)2 are, practically speaking, unlimited as long as acid is supplied. For example, consider hydrochloric:

CaCO3 + 2HCl ---> Ca++ + 2Cl- + CO2 + H2O
Ca(OH)2 + 2HCl --> Ca++ + 2Cl- +2H2O

The problem with calcium carbonate is thus not the solubility of chalk but the rate at which the reactions take place. It isn't that chalk doesn't dissolve - it's that it takes a long time to convert to bicarbonate thus upsetting the equilibrium at the particular pH so more chalk can dissolve. Thus one of the big problems with chalk is that it keeps dissolving long after we've made our pH checks. The pH keeps rising and rising until the wort is separated and the solid chalk removed. Given that the spreadsheets do not calculate the amount of chalk added to neutralize a given amount of acid correctly the slow kinematics are a mixed blessing. They protect one from overly high pH in the early parts of the mash but not the latter and one can go into the kettle with a higher pH than desired.

Just another reason not to use chalk in the mash. If you want to brew a beer that is normally made with carbonaceous water you must use carbonaceous water - not just throw chalk into the mash. In natural carbonaceous water the chalk is already dissolved by carbonic acid and you must do the same if you want the same mash/water chemistry that applied at the brewery whose beer you are trying to match. Problem is that it is a big PITA to do this but it can be done. Besides the pain brewers usually take steps to decarbonate their water so all the trouble you go to to carbonate it is a wasted effort.