I recently got hold of (well, asked for and received) a water analysis from the Perkasie Borough Authority and have been staring at it for more than a month wondering what to do with it. I've read the section on water in Palmer's How To Brew and some of his Water book. These are both excellent resources and while I have a science background, they are quite technical and I've been unable to turn all the details into an action to take, if any, on my brewing water.
The March 2015 issue of Zymurgy (cache) has an article by Martin Brungard on Calcium and Magnesium that has helped me turn knowledge into action. At the risk of oversimplyfying the guidance, I want to draw some conclusions for my use.
Some of Martin's conclusions
- A level of 50mg/L Calcium is a nice minimum for many beer styles
- You may want less than 50mg/L for lagers (wish I knew that a week ago) but not lower than 20
- A range of 10-20mg/L Magnesium is a safe bet for most beers
- Yeast starters need magnesat the high end pf that range to facilitate yeast growth
The Water Authority rep who gave me the report said two wells feed water to our part of the borough. Looking at the two wells, the Ca and Mg values are similar averaging 85 mg/L and 25mg/L respectively.
This leaves my water right in the sweet spot for average beers styles. What about some of the edge cases like IPAs and lagers.
- For lagers, next time I'll dilute the mash water with 50% reverse osmosis (RO) water to reduce the Ca to about 40. I may want to supplement the Mg to bring it back to 20.
- For IPAs, I may want to add Mg to bring it up near 40 mg/L.