I use this for every brew:
http://www.howtobrew.com/section3/chapter15-1.html
Reading in Palmer's about the mineral content "good values" and using the Brisbane brewers nomograph, plugging in the water values for Sydney Prospect water. For Brisbane I am sure someone else will have the water mineral report to use.
the brisbane brewers web site seems to be down, but try this links again a bit later:
water:
http://www.babbrewers.com/water
nomograph:
http://www.babbrewers.com/water
Using the nomograph takes a little getting used to. Start by reading the Palmer chapter.
Basically your water is too hard to brew such a light-coloured beer without any water additions (or acid rest). That means that when mashing only pilsner or base malt in the water, the resulting mash pH will be "too high" as in higher than optimal.
There are at least two ways to reduce the pH (make the water sour). One is to add something sour like citric acid or gypsum salt, another way is to leave the grains for hours, letting the grains reduce the pH naturally.
There are two things you (may) want to do, though. And reducing the pH is only one of them.
The other is to bring water mineral content to "acceptable" values as listed by Palmer.
If you use an acid rest or say citric acid (or pH 5.2) products to reduce the mash pH, you are taking care of the actual pH but ignoring the mineral content. How much this actually matters I am not experienced enough to say, but reading about this it seems to make a difference
By reducing the mash pH by adding water salts, you are
-reducing pH
-increasing calcium, magnesium, sulphates, etc
to in the case of a light-coloured beer you get low enough mash pH and the "right" mineral content for a good extraction, clear beer, increased hop crispness and whatever else is said to be related to water chemistry.
Sorry, forgot to say that the third way to reduce mash pH is to use darker grains. Darker grains are "sour" as in they reduce the pH of the water they are mashed in. So for an amber coloured beer in Sydney, we don't need to worry about mash pH, but you may or may not choose to still add water additions to deal with the low calcium, etc in the water here. Brewing a stout (again in Sydney as I don't know the water profile for Brisbane) will mean you are adding more dark grains than is necessary to get optimal mash pH, meaning the mash will be too low (too sour).
To counter-act this we add other water additions like chalk or baking powder to increase the mash pH again.
I've had much fun reading about water chemistry and trying to work out what to add for each recipe, but feel this is part chemistry and part crystal-ball kind of talk, so I always err on the side of adding a bit less than I seem to need
sorry for the long rant, guess I should have only linked to the chapter by Palmer and left it at that,
thanks
Bjorn
