Dark Stout Grain Bill with Soft Water

[prjectmayhem]

So I am wanting to brew a coffee stout with my water here in SF which is very low in alkalinity (30 ppm CO3 from water report) with a pH of about 8 out of the tap.

In the past I have been able to balance pH with a little bit of sodium bicarbonate (~0.8 g/mash), but for this recipe beer smith wants me to use calcium carbonate. I am aware of its incredibly poor solubility in water, but is there any benefit to stirring it into the mash? Would the acidic mash water solubalize the CaCO3 enough to make a significant change or would there be solid chalk floating around in the mash? Anyone ever try adjusting alkalinity this way, or just I just go back to my baking soda addition and bite the bullet for having extra sodium?

Secondly, is there any real use for calcium carbonate in home brewing if it is so insoluble?

(crossposted from All grain forum)

 

[ajdelange]

The problem with calcium carbonate is not that it is insoluble so much as that it takes a very long time to react. Thus you dump in a load of calcium carbonate, it doesn't react and you don't get the pH lowering you hoped for so you dump in more etc. Eventually, though it does react and while your mash pH may have been OK your kettle and finished wort pH may eventually climb.

Many of the popular programs exaggerate the need for alkali in dark beers. If you use enough black malt you will certainly get to the point where acid is needed but at that point you often have so much that the beer is overwhelmed with acrid bitterness to the point where people are saying that you shouldn't mash the dark grains but hold them out until the very end of the mash and then add them or steep them in the wort etc. Use reasonable amounts of dark malt and you won't have the acidity problems or the acrid, harsh "coffee that sat in the pot overnight at the office" syndrome. This is clearly an opinion and I don't do that many dark beers so please take it with a grain of salt.

Sodium bicarbonate is usually more than adequate to handle the alkalinity of mash. It isn't, of course, a good choice if your water is already heavy laden with sodium. In such cases lime (calcium hydroxide) often serves but it doesn't react that quickly either.