Q: Our brew water starts at a ph 7 with 80 mg/l CaCO3. Pretty much every mineral is stripped out of the stuff. Our beers how been turning out fine, however that doesn’t mean that there is no room for improvement. I recently stumbled upon a spread sheet developed by John Palmer in which you can figure out how much calcium carbonate, gypsum or other brewing salts you need to add to your mash to correct your ph. This spread sheet uses color as the factor for determining ph. Not understanding water chemistry fully I have been very skeptical about the use of this but have not found any more information as to how much should be added. I tried to develop an equation myself to take the ph and figure out how much calcium carbonate or gypsum I should use to change it to where I need it. Would it be better to just use a ph stabilizer and then add calcium carbonate and gypsum in amounts that cancel each others effects in an attempt to add 100 mg/l of calcium to the mash? Or is there a standard equation that I have failed to find?
A: In regards to water chemistry its always best to start with a current copy of your water analysis. If you are getting water from your city they can provide that to you, if you are using your own on-site water you will have to go to a lab with a sample. The water analysis will give you a lot of information including the rundown of pH and the major cations present, notably calcium, magnesium and sodium. The report will also give you a total hardness expressed in ppm CaCO3. This does not mean that you have that much actual calcium carbonate but the hardness is expressed that way to standardize the report with other water analyses. Surface water sources usually will have less mineral content and low hardness, in Portland Oregon the source is rainwater which has about as low a mineral content as there can possibly be and the calcium content is about 2 ppm while the total hardness is 8 ppm. Well water will usually be heavier and have higher mineral and hardness more like 100ppm calcium and 225 ppm total hardness. With a total hardness of 80 ppm as CaCO3 I am a little surprised at your low calcium content, this does not seem consistent.
Once you have the analysis you can gauge where you want to make any adjustments. Most often brewers will want to adjust the calcium level above 50 ppm in order to precipitate oxalates out and avoid gushing problems. British brewers also look at the anion component and try to maintain a ratio of 3:1 sulfate to chloride for making pale ales and 1:2 favoring chloride when making dark ales and porters. So in making the calcium adjustment you may choose to use a mixture of gypsum and calcium chloride.
There are equations to calculate the amount of minerals to add to get the desired concentration depending on whether you are using calcium chloride or gypsum and the actual mineral content already present in the delivered water. This space does not allow me to go into the series of calculations but Steve Holle’s book, A Handbook of Basic Brewing Calculations (available through the www.mbaa.com bookstore) has an excellent guide to walk you these and other key brewing calculations.
In regards to pH, your kettle knock out pH of 5.5 is pretty normal for an American ale, I am guessing your beer pH is about 4.5 which is slightly on the high side but OK, especially for malt led beers. You will not have much influence on mash or beer pH with mineral additions to the mash alone. The mash has tremendous buffering capacity and pH is difficult to adjust with minerals. If you want to acidify (decrease your pH) you are better off using sauer malt or lactic acid additions and Holle’s book addresses that as well.