The Problem
Chicago has moderately alkaline water with approximately 100 part per million (ppm) Calcium Carbonate (CaC03)(Also known as Chalk). Given my Calcium (CA) levels of 35pmm my water’s Residual Alkalinity (RA) is computed at 55. This water is perfect for brewing beers in the amber range (10-15 srm) however it is tough to brew beers lighter in color due to issues with Mash PH. The general rule of thumb is the higher the water alkalinity (roughly correlated to RA) the more appropriate the water is for darker beers. The affects of alkalinity on mash PH can be counteracted by boosting CA levels via the additions of either Calcium Chloride (CaCl2), Gypsum (CaSO4). These Calcium additions however are limited primarily because it is best to keep CA levels in a finished product below 150 ppm. While it may be possible to drive down RA far enough to brew a light lager (3 SRMish) the resulting water will most likely not yield a great tasting beer.
The Solution
One option would be to brew using all distilled or reverse osmosis water. This water is entirely devoid of any minerals and the brewer would then build the water that is appropriate to the style being brewed. This approach works perfectly however it does not work in my brewhouse because I am cheap and don’t have the time to make a water run every time I am going to brew. If you have the luxury of extra time and money you can stop reading now. However what I present costs virtually nothing and takes no additional time, only a touch of planning ahead.
The Solution my brew house is currently using Calcium hydroxide to remove Alkalinity from the brewing water. The process is described in great detail by AJ DeLange and Hubert Hangofer in a set of Home Brew Digest posts about the process. Both of these gentlemen are quite knowledgeable regarding chemistry and do a great job of filling in the details of what is going on in the process. If you are interested in all the details I suggest that you review their posts in detail. However I would like to point out that Hangofer adds:
The method is widespread among Austrian / Bavarian brewers
(geology is based on limestone, water high in temporary hardness).
It’s allowed according to Bavarian Reinheitsgebot…
The point to emphasize here it this is not a new process and has been used for many years to combat high RA water.
Enough background lets get into the details of the process.
The quick summary of the chemistry for the non-chemist
Based upon your Alkalinity and Calcium levels in your water we can calculate an amount of Calcium hydroxide to add to your water that will remove your water’s alkalinity. Where does it go? It will settle onto into the bottom of your vessel as chalk (CaC03). The remaining water will have ~ 0 alkalinity and will have a reduced amount of Calcium.
Warnings
Calcium hydroxide is a chemical and should be kept out of the hands of children and away from pets. Care should used when working with it. It can and will burn you if you handle it with bare hands. This being said it is a common addition to pickles and other food products to preserve freshness when storing. You should not attempt this process if you do not have a good gram scale with precision to .1 grams. These can be purchased for less than $20 shipped on Ebay and are perfect for measuring hops and other salt additions in your brew house.
Where to buy
Any grocery store should have Pickling Lime in the canning section near the Glass Jars. This is a great source of Calcium hydroxide because it is food grade. It should probably cost about 3 or 4 dollars for a pound. This will last you a long, long time. My treatment of 15 gallons called for the addition of 4.2 grams for 15 gallons of water. Roughly calculated I can treat 1600 gallons of water for 4 dollars.
The procedure (Simplified Version)
1. The night before. Add all your brewing water (Mash + Sparge) to a vessel.
2. Using the spreadsheet determine the amount of Calcium Hydroxide to add.
For my numbers 15 gallons of water, 100 Alkalinity, 35 calcium I needed to add 4.2 grams
2.5. Seed the water with approx 3 grams Calcium Chloride per 5 gallons of water. This will assist in precipitating out the chalk.
3. Add the Calcium Hydroxide to the water and stir.
4. Walk the hell away.
5. The following day, rack the water off your vessel into your HLT. You will notice a thin layer of white chalk on the bottom of your vessel. Be careful not to disturb this back up into solution. I was able to use my pump to clear the vessel after I had pointed my pickup up higher from the bottom. A racking cane would work as well.
6. Brew amazing beer.
The only complicated part in calculating the amount Calcium Hydroxide to add is that as part of the reaction Ca precipitates out of the solution. If you do not have enough calcium in your water not all of the Alkalinity will be removed. The spreadsheet in the tools section below will tell you on line 11 if there is a Ca deficit. I would advise that if you are planning on adding additional Ca to the mash, you should do it now. If you have a positive number on this line you should add the amount of Gypsum and/or Calcium Chloride specified at the bottom of the sheet. This will allow all the Alkalinity to be removed.
TLDR
You can use Calcium Hydroxide (aka Slaked Lime, Picking Lime) to remove alkalinity from your brewing water. Use the spreadsheets below to figure out how much to use. It works great.
Tools:
Mash Water Excel Sheet: (Downloaded from this site)
Slaked Lime Calculator Excel: (Thanks to BeirSlayer for developing the spreadsheet. Found here.)
Addtional Reading:
AJ DeLange’s Water Tretise Part 1