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Old 12-08-2012, 04:50 PM   #1
grathan
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Default Precipitating out carbonate

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?


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Old 12-08-2012, 05:14 PM   #2
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Originally Posted by grathan View Post
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

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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.


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Old 12-08-2012, 06:33 PM   #3
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OK, related question. If I boil my strike water will that do anything to the ions? I donít 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?
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Old 12-08-2012, 07:06 PM   #4
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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.
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Old 12-08-2012, 07:35 PM   #5
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Ah, thatís what I guessed. My tapwater is moderately hard and the hardness (85-168) and the alkalinity (99-123) are roughly equal. I donít see any precipitate but it has to be there.

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

So, can I conclude that if I boil and donít 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 isnít 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, Itís fun as always.
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Old 12-08-2012, 08:40 PM   #6
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Quote:
Originally Posted by Wynne-R View Post
Ah, thatís what I guessed. My tapwater is moderately hard and the hardness (85-168) and the alkalinity (99-123) are roughly equal. I donít 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.

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So, can I conclude that if I boil and donít 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.


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Eventually the CaCO3 will dissolve back in the boil. But isnít 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.
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Old 12-09-2012, 05:40 PM   #7
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Quote:
Originally Posted by ajdelange View Post

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!
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Old 12-10-2012, 03:31 PM   #8
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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.

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Old 12-10-2012, 03:41 PM   #9
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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.
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Old 12-10-2012, 04:27 PM   #10
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Wow, guys, thanks for all the help! I had tried this without decanting a couple of times and couldnít see that it did anything. Having said that, thereís nothing magic about boiling; some of this is going to happen at 72C strike, isnít 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 itís the strike water, I donít 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 youíre going to acidify the water do it now. Just keep in mind that your need for acid is less.

Iíve been using 2 mL of lactic acid for my mash making pales, so Iím 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 Iíll 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, yíall.


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