Cheers TartanSpecial. Well on the subject of 'carbonate', obviously not for your benefit but because some might like to know and because I'm mid-rant...
'Carbonate' is a way of expressing 'alkalinity'. So I've already mentioned it can be measured as "CaCO3": Well 'hardness' is the Ca bit, "alkalinity" the CO3 (carbonate) bit. 'Alkalinity' is important for increasing pH in the mash (not really its flavour impact). A mash could be too acid (<pH5.2ish) because it contains lots of acidic roast grains.
So you add chalk or baking soda to increase alkalinity (reduce acidity) - which? Depends on if your mash can stand more calcium (chalk) or sodium (baking soda). But what about CO3 (chalk) or HCO3 (baking soda)? Doesn't matter, balance of CO3 and HCO3 finds its own equilibrium depending on conditions (such as pH), but it'll mainly ends up being HCO3 in a mash. So you decide to add chalk. First thing you notice is it wont (barely) dissolve! Well one form is called "precipitated chalk" so that shouldn't be a surprise. Some add it direct to the mash where the conditions will help it dissolve a bit and the remainder you can't see anyway! All that careful weighing, and chalk will make a mockery of it. Don't even think of adding it to your sparging water! Or any alkaline salts for that matter.
Just don't bother with this stuff unless you've got a "too low pH" problem. Even then you are better with slaked lime than with chalk (BUT it is hazardous, it burns, and very easy to overdose).
What helped me is "Bru'n Water" which is a freebie (or send him 5-10 dollars or so for a more up-to-date version). But its fairly involved, but then again, if you've read this far...
