Slaked Lime added to boil

Is there any disadvantage to adding slaked lime to the boil kettle for the sole purpose of raising the calcium content? I am talking about perhaps 1tsp or so of it. Our water is a little deficient in it (30ppm calcium).

 

No! It adds calcium but it also increases wort pH dramatically as it's a strong base. When people add calcium to wort it is usually in an attempt to decrease wort pH and, therefore, they use the chloride and/or sulfate. Should you, however, find that you want to increase wort pH then lime would be a good way to do that.

 

Is there anything that would add calcium without affecting ph?

 

If there is residual phosphate in the wort (and there usually is) adding calcium ion from any source will result in a reduction of pH through precipitation of calcium phosphate (apatite). That's why brewers typically add it. If your water is low in calcium (and 30 mg/L isn't that low though higher is often desirable) the time to add it is when mashing as this will lower mash pH to some extent and that's beneficial except when the beer is dark.

 

That was my concern as well. Ok, so it can work but the caveats you mentioned.

Hmm, what about this: I normally use calcium chloride to supply both the reduction in mash ph and a bit of calcium. Getting the appropriate amount of calcium requires a fair amount of calcium chloride. But then the chloride increases. I don't know at which level I need to be concerned, but out of the tap it is about 25 ppm. Is there any detriment to adding the lime to the mash and simply increasing the amount of lactic acid to balance the increase ph, thereby avoiding the need to add excessive amounts of calcium chloride? Generally its seems that somewhere around 2.5ml of 88% lactic acid will balance about 1 tsp of lime.

 

What you are fighting here is the fact that you can't add just calcium to water. Well, you can but it reacts with the water to form calcium hydroxide so you are effectively adding slaked lime. If you want to add lime but don't want an increase in pH then indeed acid must be added but the net effect if you add sulfuric acid is calcium sulfate and the net effect if you add lactic acid is calcium lactate etc. Of course with a pH meter in hand you can titrate to any pH you desire. The danger with lactate addition is, of course, that lactate is a flavorful ion. If you are bent on this approach phosphate would probably be a better acid choice as it is pretty flavorless (as is calcium).

One tsp of lime weighs perhaps 5 grams (guessing here) and thus supplies 5000(mg)*2(mEq/mmol)/74(mg/mmol) = 135 mEq (OH-). 88% lactic weighs 1.206 g/cc so 2.5ml contributes 2.5(ml)*1206(mg/mL)/90.1 (mEq/mg) = 33.5 mEq H+. So unless lime is a lot fluffier than my guestimate it's going to take appreciably more than 2.5 ml of lactic to neutralize a tsp of it.

The other side of the coin is that when people are encouraged to add calcium chloride to their mash water it isn't really for the calcium but rather the chloride which in general improves the flavor and body of most beers. You can overdo it, of course, and that kind of flavor and body are not appropriate for all styles.