Is there any kind of temp correction factor for adding acid to strike water or the mash and/or sparge water after the water/mash has been heated above room temp?
Adding Acid to Warm/Hot Water
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No. There isn't. Nor should there be if the calculation of the amount of acid is done correctly.
The approach we take in home brewing is that while the reactions take place at mash temperature we do all pH measurements at room temperature. We calculate the amount of acid required on the assumption that if we get the a certain measured pH at room temperature the pH, though different at mash temperature, will be optimum or near optimum. So we do calculation of the amount of acid needed based on room temperature but, when it comes to the malt, we deduce its properties as used in the calculations from measurements made at mash temperature and reduced to room temperature according to what I call the pH glide which is the change in the malt's DI mash pH as the mash is cooled. It varies from malt to malt. None of the popular spread sheets take this into account AFAIK as it does complicate things somewhat.
Most acids are 'stronger', in the sense that they yield up more protons at higher temperature than at lowewer, but hydrochloric and sulfuric, for example, are so strong that they can be considered to yield all their protons at any temperature we may be interested in in brewing.
Lactic acid is a different animal. At 20 °C a millimole of it yield, tp mash pH 5.4 at room temperature 0.9732 mEq of protons. At 50 °C it yields, to mash pH 5.4 about 0.9614, a little more than a percent less. But them mash pH at room temperature of 5.4 is likely to be something like 5.2 at 50 °C and to pH 5.2 1 mmol of lactic acid only yields 0.9402 mEq protons. This is more than 3% less. Thus, were we to work at mash temperature in doing our acid calculations the we would probably want to add 3% more acid that we would based on calculation at room temperature.
Phosphoric acid is also temperature dependent. A millimole of that at room temperature yields 0.9342 mEq to pH 5.4 whereas at 50 °C it yields 0.9289 to pH 5.2. In this case it is less than a %.
Changing their spreadsheets to account for this would require spreadsheet authors to incorporate a lot of additional chemistry which would complicate their products greatly. And that extra effort is probably not justified as they are guessing at malt acid based properties based on tenuous assumptions that they are linear with pH, highly correlated with malt color etc. Thus the answer is, apparently, that we should take change in acid strength into cosideration when calculating the amount needed but don't because it's too hard and probably isn't justified in terms of the other things we ignore.
Another aspect of this is that a mole of acid is a mole of acid whether it is being added to hot or cold water. So one must be sure that he knows his acid concentration w/w and density at the temperature he is measuring out the acid however he calculated the mmols he needs.
The approach we take in home brewing is that while the reactions take place at mash temperature we do all pH measurements at room temperature. We calculate the amount of acid required on the assumption that if we get the a certain measured pH at room temperature the pH, though different at mash temperature, will be optimum or near optimum. So we do calculation of the amount of acid needed based on room temperature but, when it comes to the malt, we deduce its properties as used in the calculations from measurements made at mash temperature and reduced to room temperature according to what I call the pH glide which is the change in the malt's DI mash pH as the mash is cooled. It varies from malt to malt. None of the popular spread sheets take this into account AFAIK as it does complicate things somewhat.
Most acids are 'stronger', in the sense that they yield up more protons at higher temperature than at lowewer, but hydrochloric and sulfuric, for example, are so strong that they can be considered to yield all their protons at any temperature we may be interested in in brewing.
Lactic acid is a different animal. At 20 °C a millimole of it yield, tp mash pH 5.4 at room temperature 0.9732 mEq of protons. At 50 °C it yields, to mash pH 5.4 about 0.9614, a little more than a percent less. But them mash pH at room temperature of 5.4 is likely to be something like 5.2 at 50 °C and to pH 5.2 1 mmol of lactic acid only yields 0.9402 mEq protons. This is more than 3% less. Thus, were we to work at mash temperature in doing our acid calculations the we would probably want to add 3% more acid that we would based on calculation at room temperature.
Phosphoric acid is also temperature dependent. A millimole of that at room temperature yields 0.9342 mEq to pH 5.4 whereas at 50 °C it yields 0.9289 to pH 5.2. In this case it is less than a %.
Changing their spreadsheets to account for this would require spreadsheet authors to incorporate a lot of additional chemistry which would complicate their products greatly. And that extra effort is probably not justified as they are guessing at malt acid based properties based on tenuous assumptions that they are linear with pH, highly correlated with malt color etc. Thus the answer is, apparently, that we should take change in acid strength into cosideration when calculating the amount needed but don't because it's too hard and probably isn't justified in terms of the other things we ignore.
Another aspect of this is that a mole of acid is a mole of acid whether it is being added to hot or cold water. So one must be sure that he knows his acid concentration w/w and density at the temperature he is measuring out the acid however he calculated the mmols he needs.
OP
OP
Soooo, if I measured out the amount of acid (lets say 88% Lactic) that a calculator like BrunWater says I should add but for some reason forget to add it before heating, I'm OK to do so after heating without too much worry? I ask this because of the footnote in BrunWater that states: "For best results, add acids prior to heating the water since heating can drive off a portion of the alkalinity that the acid addition was calculated to remove." To me as a dumb layman, it would seem the risk would be potentially driving the pH too low based upon that note. Am I overthinking it?
If your water is hard and most of the hardness is temporary (bicarbonate) then heating will cause precipitation of chalk and escape of CO2. These things will combine to remove alkalinity and this is a common technique for doing so. If your water is like this then by all means heat it and let the chalk precipitate before adding any acid. Decant the water off the precipitate and then add the acid according to the reduced alkalinity (it will be about 50 ppm but measure with a test kit if possible), not the original alkalinity. If you add the acid before heating then you are effectively converting alkalinity (bicarbonate) to the anion of the acid you are using. It is better to remove as much alkalinity as possible before adding acid so as little acid as possible can be used. An exception to this would be where the alkalinity (in meq) just equals the total amount of sulfate and/or chloride you want to add and you have those acids in food grade available.
OP
OP
If I understand the definition correctly, my water is not hard. According to my municipal water reports for the past 3 years, the Bicarbonate level on avg is 58.3 mg/L, Carbonate is zero, and Calcium is 24.5 mg/L.
As mentioned, the alkalinity of SOME waters can change when they've been heated. While you can make some assumptions for the reduction when the water is boiled and decanted, it becomes much more difficult to estimate or predict what the resulting alkalinity is when the water is only heated to strike or sparging temperature. There may or may not be alkalinity reduction. For that reason, I've made the blanket recommendation for all brewers to add acids to their water before heating. That way, the alkalinity measured in the room temperature water can be properly applied when calculating the acid dose.
For brewers using water with low temporary hardness, this whole issue is almost moot. Their water's alkalinity is not likely to change much upon heating. But since most people wouldn't know if their water does or doesn't have much temporary hardness, I've aired on the side of caution for all brewers to add acid before heating their water.
For brewers using water with low temporary hardness, this whole issue is almost moot. Their water's alkalinity is not likely to change much upon heating. But since most people wouldn't know if their water does or doesn't have much temporary hardness, I've aired on the side of caution for all brewers to add acid before heating their water.
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OP
OP
Thanks gents! Just trying to understand the whole water chemistry thing (to include the tools) better-- not an easy task for a mouth breather like me. 
Your alkalinity is less than 1 mEq/L and your calcium slightly over 1. It is, therefore, very unlikely that heating will result in any reduction in alkalinity and you can, therefore, proceed without any fear of a problem from that aspect of it or from the acid vs temperature aspect either.
I like to say that the chemistry is not difficult but that it is intricate. IOW there are lots and lots of little details that need to be understood to fully grasp the subject so be prepared to invest some time.
danielcook
Member
According to the latest Seattle water report, the total alkalinity is 21 and the calcium level is < 1 mg/L. Bru'N Water calculates bicarbonate concentration at 25 ppm. In other words, soft as a baby's cheek. From this, and the above discussion, I assume that my local water also allows me to acidify my sparge water after it's already been heated. This is good, because at my next brew I plan to get my sparge water from my home's water heater rather than heat it from the municipal source. 40+ total gallons of water (mash + sparge) take an annoying long time to heat, especially in the colder months, and I figure I can shave a good 90 minutes from the brew day this way.
Yes, that water's alkalinity is so low that boiling won't change it. Adding acid to hot water shouldn't affect your results.
With alkalinity that low (0.4 mEq.L) you don't need to acidify your sparge water at all. If you do so it will take a fine hand with the acid.
If your water heater is a Rinnai or Navien or sometjhing like that (tankless) you will be in good shape taking your sparge water from the water heater. If it is a more conventional (tank) heater take a glass of water from it, let it cool and taste it before using it in your beer.
I guess this is also a good place to mention that should a brewer (with more alkaline water than danielcook's) choose to use warm/hot water from a tankless heater for the mash he can allay any fears about it having lost alkalinity via heating (if it did part of that alkalinity will be deposited inside his expensive Navien which will protest when it builds up enough) simply by acidifying not by adding a calculated amount of acid but by adding acid until the water pH reaches the desired mash pH. This effectively sets the alkalinity to 0 and compensates for any variance in the water's alkalinity from any source (the value in the city's last report or what was on the last Ward Labs report may be quite different from what is coming out of ther tap depending on where the water comes from). Tell the spreadsheet that the water's alkalinity is 0. It will calculate additional acid needed to neutralize the grains.
Obviously, in cases (dark beers) where it calls for alkali the equivalent acid should be removed from the water and the amount removed deducted from the alkali requirement. IOW it's a bit trickier in those cases. I won't get into the details here.
If your water heater is a Rinnai or Navien or sometjhing like that (tankless) you will be in good shape taking your sparge water from the water heater. If it is a more conventional (tank) heater take a glass of water from it, let it cool and taste it before using it in your beer.
I guess this is also a good place to mention that should a brewer (with more alkaline water than danielcook's) choose to use warm/hot water from a tankless heater for the mash he can allay any fears about it having lost alkalinity via heating (if it did part of that alkalinity will be deposited inside his expensive Navien which will protest when it builds up enough) simply by acidifying not by adding a calculated amount of acid but by adding acid until the water pH reaches the desired mash pH. This effectively sets the alkalinity to 0 and compensates for any variance in the water's alkalinity from any source (the value in the city's last report or what was on the last Ward Labs report may be quite different from what is coming out of ther tap depending on where the water comes from). Tell the spreadsheet that the water's alkalinity is 0. It will calculate additional acid needed to neutralize the grains.
Obviously, in cases (dark beers) where it calls for alkali the equivalent acid should be removed from the water and the amount removed deducted from the alkali requirement. IOW it's a bit trickier in those cases. I won't get into the details here.
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