If you won't listen to Yooper and her 61,000 posts, I don't know what hope I have, but...
-Waiting for Martin Brungard [edit-fixing the spelling of Martin's last name; sorry about that, I'm used to the Dutch double A's] and AJ to jump on this one..
If you've got access to it, pull up Martin's fairly recent (past year) article on "Dublin" water profiles in Zymurgy. He dispels many of the prevalent myths of the "dublin profile".
A couple of snippets:
"While hard and alkaline waters are present in many areas of Ireland, the country's softer and less alkaline waters are the key to its successful brewing history...."
"herefore, the geologic map can also be used to describe where softer, low alkalinity water supplies are likely to exist. For the major Irish brewery cities noted previously, the map shows that soft, low alkalinity water is probably available. In the case of Dublin, that assumption is not as apparent and a closer review of it's water supply is needed."
One of his major points is that Dublin is supplied by two water sources coming from different areas with VERY different geology and therefore different waterprofiles; water coming from the midlands, if I remember correctly via the Liffey (which runs smack dab through the center of Dublin West to East) would generally be rather hard, but the Grand Canal and several reserviors and aquaducts also provide relatively soft water from the Wicklow mountains to the south of Dublin. -St. James Gate has access to both Liffey Water and Grand Canal; the Grand Canal passes within 3/4th of a mile of the brewery.
Martin also theorized that this soft Grand Canal water probably recharged any underground well that Guinness may have used and the resulting water would have some hardness from the Liffey but dilluted by the Grand Canal water.
The original location of the first Guinness brewery was in Lexlip and had soft Wicklow water, too.
There's also the far more practical issue of whether Guinness even used the water available "as is" or treated it; certainly they treat it today. I'd theorize with the widely fluctuating water supply that they likely had, they'd certainly be tracking it closely and treating it to provide consistency; especially in a major multinational brand where consistency is everything. (The global Guinness breweries aren't even allowed to produce their own wort; Guinness concentrates it into wort extract they call "the essence of Guinness" and ship the syrup in stainless tankers to their global "breweries" where they rehydrate and ferment it (often at different strengths than the St. James Gate versions).
"The long-cited hard and alkaline Dublin water profile is not representative of the water sought for most brewing in Ireland. It is apparent that soft, low residual alkalinity water was used in several cities to create the signature beers of the country."
And now the practical advice with some modifications that I've made myself (noted where applicable):
[*]Flavor ion concentrations are low and should not be notable in the beers. The concentrations in the Dublin and Wicklow profiles provide guidance.
[*]Dry stout brewing should use low alkalinity water and use separate base malt and roast malt mashing/steeping. Combine the worts after mashing / steeping.
[*]A kettle wort pH (Adam Assumption: Pre-boil ph) of 5.0 to 5.2 is recommended for dry stout brewing to provide tart and crisp flavor. Kettle wort pH for other beer styles is typically 5.3 to 5.5.
[*]Higher alkalinity water is suitable for brewing other stout and porter styles, not dry stout. The excessive alkalinity of typical Dublin profiles may not be suited for any brewing. (Adam: Pre-boil!)
[*]Mashing all grains together is suitable when brewing other stout and porter styles using higher alkalinity water.
[*]A kettle wort pH of 5.5 to 5.6 can help extract more flavor and color from roast malts and smooth their flavors. This higher pH may be preferred in these other stout and porter styles.
[*]The pre-boiling calculation can be used to estimate what the ending calcium and bicarbonate concentrations might be when starting with high alkalinity water. Use the calculated values to amend the high-alkalinity water to reflect that treatment.
-I lived in South Dublin for 5 years and have been very involved in the early craft brewing movement there so it's a subject I've heard discussed many, MANY times and pulling my own water report when I lived there revealed just how wrong the "Dublin" profile is vs. what most people around Dublin are getting from their tap, yet along from what Guinness actually used (and it's HIGHLY likely that they treated and certainly treat their water today).
Feel free to reach out to the fine folks @ Beior.org -Irish Beer Consumers Union and HomeBrewers Forums or NationalHomeBrewclub.com -newer organization solely focusing upon home brewing in Ireland for more discussion on Irish Stout brewing and certainly Irish water and what water was / is used.
If you were a brewer and your water source was actually as insanely alkaline as the paper-based "Dublin profile", you'd certainly pre-boil it because it would be a beast to brew with otherwise (and to clean your equipment with, for that matter). Your "actual" water profile would then be change to whatever this post-boil profile was, but again profiles are a pretty bad idea with even worse "data" on what those profiles are/were.
The biggest key lesson you can take away is that blindly following the city-based water profiles are for suckers; many a brewer has been burned by these theoretical profiles in the past. They will trip you up more than you'll help you. They're an interesting footnote in our collective homebrewing history, but not a particularly positive one. Having said that, understanding the major characteristics of international brewing cities can highlight some important features of the traditional brew from that region; just don't blindly follow the traditional "profile" or you might end up with salty, acidic, or sulfury bad beer instead.
Adam
