I'm wondering about this idea: that we do not know what treatment occurred within the brewerys that used these famous ancient water sources.
In some cases we do know. Martin has done a fair amount of research on this in coming up with profiles for his spreadsheet. For example, I learned at the NHC earlier this summer, that the Burton brewers heated the water in the HLT before doughing in. Having synthesized Burton water (from a physically feasible profile) I know what happens if you do that. Lots of the carbonate drops out. I still get razzed by a guy that helped me brew an 'authentic' Burton ale by this method. He saw all the salts go in and witnessed the extensive sparging with CO2 necessary to get them dissolved and then watched them drop to the bottom of the HLT. He thought this a great waste of time and so do I. I would only do this for a class and that's exactly why I did it. This is another of the reasons it is generally foolish to try to emulate a given water.
Since almost nothing was known about water chemistry until the late 19th and early 20th century, water treatment was mostly done by physical means (distilling, diluting, or filtering) for as late as the 1950s and 1960s.
The breweries of yore would not invest the energy required to distill, and had no low ion source of dilution water. As noted in the Burton case, they did invest the energy to heat the water as they had to anyway and this, because their water is super saturated with respect to lime, caused partial decarbonation to take place. As science came into the picture many adopted lime softening and I expect that's still used today though the tendency seems to be more towards RO and microfiltration.
So I ask, was the water treatment processes that occurred in ancient brewerys likely done by distillation, dilution, and/or filtration? And, if so, it is the extent of treatment that is unknown, but we do know the likely processes used.
I obviously don't know what went on in any particular brewery in the past but as noted above I'd guess that filtration would be the only process used and that wouldn't change the chemistry of the water.
What is also known is this:
1. the water chemistry profile at the source.
I don't think that is known. I have perhaps 8 profiles for Burton wells. There is definitely more than one well in Burton which has been used as a source of brewing water. As I noted in the other thread most of those profiles don't balance chemically.
You could argue that the chemistry of the Isar has not changed over the years but I would question whether the water I sample out of the tap in a hotel in Munich is more than just broadly similar to the water the monks used to brew the traditional Munich styles. The effects of acid rain in industrial Europe have surely changed the chemistry of this river's water.
2. the challenge and cost of bringing large quantities of water from an alternate source (likely from miles away) would limit the ability to change the chemical content of the source water, except by distillation or filtration. (Dilution with distilled water would decrease concentration but not the ion ratios.)
Transportation of water is clearly out of the question because of the weight. This is why we have the beer styles we do today - they were in large part driven by the qualities of the available water. Breweries were located where the water was good but without the abilities we have today the kinds of beer that could be brewed were limited.
Filtration does not change the ion content of water. There were no ion exchange resins in those days. Xeolites did, of course, exist then but I don't believe ion exchange technology was available outside the laboratory until well into the 20th century.
3. Distillation is a labor intensive process, so it had limited application for changing water.
I'd guess none. It is not only labor intensive but requires energy and capital equipment.
4. Filtration, in general, does little to change water chemistry profile.
True
I conclude that it is likely that many, if not all, ancient brewerys did indeed use the water as it came from the source, ie, with no treatment.
Other than decarbonation by heating that's probably true. But certainly we must allow that the Munich brewers, for example, in the development of Helles, figured out some way to beat the bicarbonate. Now did they do that by decarbonation by heating, by lime treatment, by the use of sauergut (lactic acid) or a combination of these? I don't know.
And therefore, it is important to know the actual ion concentrations of these famous water sources.
I don't think you can draw that conclusion. Even if you could there is no way to get the info you want as analytical techniques were crude in the earlier days. Sørenson didn't even come up with the concept of pH until 1909 so there isn't going to be any alkalinity data on any water samples taken before that. And, as mentioned before, the water data that we do find in textbooks and elsewhere is frequently demonstrably flawed.
How else is there to see this?
I advise people setting out to brew, for example, a Burton beer, to learn as much as possible about the water with which this beer was brewed. Research will hand you a bunch of 'profiles' for Burton water which vary widely in reported bicarbonate content but less so in sulfate. We know that the ales brewed with this water were pale and so we must conclude that the bicarbonate was somehow dealt with. RA calculations show that the suite of profiles had RA's ranging from 0 to as low as -100. Thus we know that the water's must have had a lot of permanent hardness - no surprise given the high sulfate levels. We conclude that Burton water must have been very gypseous. Experience shows that if one synthesizes Burton water heating will cause precipitation of much of the bicarbonate (with all that calcium to balance all that sulfate this is no surprise). So the only question is as to whether the Burton brewers doughed in cold and heated the mash (this would cause the chalk to precipitate in the mash) or heated to strike in an external vessel which would cause the chalk to precipitate in the HLT and not reach the mash. I got confirmation recently that it is the latter (which really only makes sense as it's easier to heat water than mash). Thus we conclude that we can make up a suitable water for brewing Burton beers by adding some gypsum and calcium chloride to low ion water. The question is 'How much?' and the answer is 'As much as is necessary to get you the optimum beer
by whatever your criterion of optimality may be.' That last phrase is in italics because many people don't think about this aspect of it. Some optimality criteria are:
1. You like it
2. Your spouse likes it
3. Your buddies like it
4. It wins BOS
5. It sells (commercial operations)
6. It is authentic
Beers that satisfy these different optimality criteria can be quite different but still all be Burton ales. I mentioned earlier classes I have given where I synthesized 'authentic' Burton water, brewed an ale with it and then brewed the same ale (or as nearly the same as I could) with my untreated well water. Tasters mostly found the Burton water beer more authentic (though how they knew that I can't fathom) but the less gypseous water ale a much better beer.
To summarize: the way to look at this is that the styles usually have some characteristics driven by the water available to the original brewers. While you don't know the details of what the original water chemistry were nor how the brewery processed it you can learn the general characteristics of the water and as you have infinite control over the water you brew with (assuming you start with DI or RO) you can synthesize a water with the general characteristics and then tweak the ion contents in order to meet your optimality criterion. It is possible for you to make a better Burton ale than the Burton brewers ever did.