Precipitating out carbonate

[grathan]

It is said to deal with high carbonates by boiling the water which releases the c02 from solution dropping out calcium flakes and then transferring off the sediment to get a liquor lower in carbonate.

Does not this same thing happen when you boil wort for an hour and then chill and transfer off the kettle gunk?

 

[ajdelange]

It is said to deal with high carbonates by boiling the water which releases the c02 from solution dropping out calcium flakes and then transferring off the sediment to get a liquor lower in carbonate.

It is actually calcium carbonate that precipitates:

Ca++ + 2HCO3- ---> H2CO3 + Ca++ + CO3-- ---> CO2 + H2O + CaCO3

Does not this same thing happen when you boil wort for an hour and then chill and transfer off the kettle gunk?

No, for a couple of reasons. In the first place kettle pH is usually 5.2 or less. At pH 5.2 there is little carbo left assuming that you boiled the water first, none, practically speaking, of what is left is carbonate (94% is carbonic acid and 6% bicarbonate ion) so there is nothing to coalesce with calcium to from chalk. Secondly, the calcium ion concentration is somewhat depleted. If it is present in the mash it will preferentially combine with phosphate

10Ca++ + 6H2PO4- + 2H2O ---> Ca10(PO4)6(OH)2 + 14H+

as apatite is much less soluble than chalk.

There may be further precipitation of apatite in the kettle if calcium and phosphate are not completely precipitated in the mash tun and especially if you add a calcium salt(s) to the kettle. This is sometimes done to effect further pH reduction in the kettle though sometimes acid is added for this purpose.

 

[Wynne-R]

OK, related question. If I boil my strike water will that do anything to the ions? I don’t have any way to decant the strike water. I guess the precipitate would eventually dissolve in the mash and the boil, but it could take a while.

Is that going to affect the mash or am I just wasting electricity?

 

[ajdelange]

That depends what ions are present. Assuming potable water the only ions that will be effected by boiling are calcium, magnesium, bicarbonate and carbonate. The reaction in #2 will take place as will a similar reaction for magnesium. Potable water may contain some phosphate as well and if there is enough calcium and the pH is high enough some apatite may precipitate too.

The reason for boiling water is to reduce alkalinity. The bicarbonate converts to carbonate and falls out as chalk. If you don't decant you are putting that alkalinity into the mash tun which is the opposite of what you want to do. You would get some benefit as it takes a long time for chalk to dissolve - the pH degradation will not be as great as it would be if you didn't boil but chalk is the gift that keeps giving in the sense that it will continue to dissolve as long as it is in the beer i.e. well past the mash tun.

There is always a way to decant water even if is no more sophisticated than dipping it out with a cup or pitcher. Use of a siphon is obviously a workable method.

 

[Wynne-R]

Ah, that’s what I guessed. My tapwater is moderately hard and the hardness (85-168) and the alkalinity (99-123) are roughly equal. I don’t see any precipitate but it has to be there.

Alright, technically I can decant, I just don’t have anything to put it in. I suppose I could dump it into a bucket. I’d rather not. I imagine breweries of old had the same problem, as big old pots aren’t cheap.

So, can I conclude that if I boil and don’t decant I will lower my alkalinity by an unknown and unpredictable amount in the mash? Eventually the CaCO3 will dissolve back in the boil. But isn’t the mash pH way more critical than the boil? I would think the boil would pretty much take care of itself.

I guess I could figure this out experimentally by measuring the mash pH.

Thanks AJ, It’s fun as always.

 

[ajdelange]

Ah, that’s what I guessed. My tapwater is moderately hard and the hardness (85-168) and the alkalinity (99-123) are roughly equal. I don’t see any precipitate but it has to be there.

Yes, it is. But the particles are too small to be seen with the naked eye. A turbidity meter would reveal an increase.

So, can I conclude that if I boil and don’t decant I will lower my alkalinity by an unknown and unpredictable amount in the mash?

The alkalinity will go down, typically, to the point where whichever of the hardness or alkalinity is smaller reaches 50 ppm as CaCO3.

Eventually the CaCO3 will dissolve back in the boil. But isn’t the mash pH way more critical than the boil? I would think the boil would pretty much take care of itself.

The mash is the most critical point but the pH throughout the rest of the process is important too. That's why it's such a bad idea to use chalk to control mash pH. Not all the chalk dissolves during the mash and the brewer thinks all is OK. Then after the mash (lauter, sparge...) the remaining chalk continues to dissolve raising the pH post mash to higher than what it would be if chalk had not been used. The same would probably happen if you boiled and then used the water without decantation.

 

[mabrungard]

The mash is the most critical point but the pH throughout the rest of the process is important too. That's why it's such a bad idea to use chalk to control mash pH. Not all the chalk dissolves during the mash and the brewer thinks all is OK. Then after the mash (lauter, sparge...) the remaining chalk continues to dissolve raising the pH post mash to higher than what it would be if chalk had not been used. The same would probably happen if you boiled and then used the water without decantation.

+1 on these points. Boiling without the opportunity to decant could improve the mash pH performance only to eventually contribute its proton neutralization capability in the boil or fermenter with unfavorable effects. Probably the most important ill effect is the degradation of hop character and bittering that is typically referred to as 'roughness' in the flavor. The second effect would be the increase in beer pH with a potential loss in crispness in the flavors.

Chalk, the buffer that keeps giving!

 

[Kaiser]

Wynne,

To enhance the precipitation of alkalinity during boiling you should also add some calcium salts (CaCl2 or CaSO4, or both) to boost your calcium levels. If your water hardness matches the alkalinity you could potentially remove all Calcium and alkalinity from the water since there is enough of each to form chalk. In practice that won’t happen but you will still end up with low calcium water.

Kai

 

[ajdelange]

Remember that when calcium carbonate is in equilibrium with water and atmospheric CO2 the hardness and alkalinity will each be at about 1 mEq/L (50 ppm as CaCO3). By raising the calcium level you can get somewhat below that but not a great deal.

 

[Wynne-R]

Wow, guys, thanks for all the help! I had tried this without decanting a couple of times and couldn’t see that it did anything. Having said that, there’s nothing magic about boiling; some of this is going to happen at 72C strike, isn’t it? Folks with lots of temporary hardness are lowering their mash pH a little.

OK, let me recap to make sure I have it right and for the folks following along at home:

1 Boil the hot liquor tank along with the calcium additions. In my case it’s the strike water, I don’t have anything big enough to hold all the liquor.

2 Carefully drain the tank, leaving the last liter or so. Pitch the last bit.

3 If you’re going to acidify the water do it now. Just keep in mind that your need for acid is less.

I’ve been using 2 mL of lactic acid for my mash making pales, so I’m guessing I could cut that in half with this method. I have been concerned that at 2mL the taste was slightly too much for a delicate pale.

I guess I’ll siphon the liquor off with a racking cane with the little knob thing on the end. That should give me a good shot at sneaking the liquor past the insidious invisible precipitate.

In case anybody is wondering, I use RO for the sparge. Thanks again, y’all.

 

[Kaiser]

Not much of this is happening at 72C unless you heavily agitate the water to purge its CO2.

You may also want to add some chalk to the boiling water. This will act as nucleation sites for the precipitation and increases its efficiency.

If your water responds well to boiling, you may want to look into slaked lime treatment. It does the same thing w/o the energy needed to boil water and you can perform it in a large plastic vessel.

Kai

 

[ajdelange]

I'll just add that if the water doesn't turn cloudy that means that the particles are so small that they will stay in suspension so that even decanting isn't going to do much for you. Adding the chalk for nucleation sites may improve the situation because the CaCO3 that does precipitate will preferentially form on those chalk particles and those should settle out. To really see what is going on you would need to get an alkalinity test kit or put one together yourself and measure the before and after boiling alkalinity levels to see if you are wasting time and energy (yours and electric).

Given that you have RO water available a much simpler way of dealing with alkalinity is to simply dilute it away. If you have alkalinity of 100 and dilute 1 part RO with one part mains water you will lower the alkalinity to 50. Everything else will be cut in half as well so you will most probably need to supplement calcium, chloride and perhaps sulfate.