I just finished reading the excellent article on the smoked wheat beer, Gratzer in the Nov/Dec 2012 Zymurgy issue. Since a Gratz water profile was included in the article, it got my interest.
As with many water profiles from historic brewing cities, the uninformed use of those water profiles can get you into trouble. The Gratz profiles included in the article are cases in point. Of those Well samples in the article, only Well #2 comes close to balancing and it requires an assumption to achieve that balance. The assumption comes for the Alkalinity. Unfortunately, it appears that the alkalinity should have been labeled HCO3 instead since the profile does not come close to balancing with 325 ppm (as CaCO3) Alkalinity. So, the Gratz water profile can be reasonably assumed to have the following profile:
Ca: 121 ppm
Mg: 31 ppm
Na: 32 ppm
SO4: 145 ppm
Cl: 67 ppm
HCO3: 320 ppm
Fortunately in the case of this light-colored wheat beer, trying to duplicate the bicarbonate (HCO3) content is pointless. That water is far too alkaline to brew this pale beer. Fortunately, the simple process of boiling the Gratz water would result in the following profile that is more suited to brewing this style:
Ca: 45 ppm
Mg: 31 ppm
Na: 32 ppm
SO4: 145 ppm
Cl: 67 ppm
HCO3: 80 ppm
This reduces the alkalinity significantly and creates Residual Alkalinity conditions that are reasonably suited for brewing this beer. The article goes on to say that an Acid Rest was used in the brewing. That should further neutralize the HCO3 and make the water more suited to this pale style and make the finished beer more tart and spritzy. That effect can be parroted with a minor addition of lactic acid. I'd say enough acid to neutralize about 20 to 30 ppm of the HCO3.
This sure looks like an interesting beer. I love session and smoked beers and this should be something enjoyable. Try it out with these water recommendations and you should be in the ball park.
That entire issue was really enjoyable and information packed. If you are not an AHA member, I can assure you that AHA dues provide quite a return. Seriously consider joining.