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Old 01-03-2014, 09:01 PM   #11
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Enter the first chart below with your water pH and alkalinity. The 7.45 and 110 lines intersect between the 2 and 2.5 lines at about 2.3. This is your carbo per liter. Now look at the second chart and read off the charge at 7.45 ( about - 0.9 ) and at the mash pH you want - 5.4 gives - 0.1. The difference, 0.8, multiplied by the carbo, 0.8 * 2.3 = 1.84 is the amount of acid you need to add to each liter to get your water to pH 5.4. 1 L of lactic acid weighs 1206 grams and contains 1206/90.08 = 13.38 moles. Lactic acid is strong enough that at pH 5.4 it is almost completely dissociated thus it is 13.4 N and 1 mL yields 13.4 mEq protons. For 5 gallons, 19L, you need a total of 19*1.84 = 35 mEq and at 13.4 per mL thats 35/13.4 = 2.6 mL. That's all there is to it.

If you had a chart similar to the second you can do the same to calculate the amount of acid you need for the base malt. As you don't the best you can do is WAG that at about 35 mEq/pH-kg. Subtract the desired pH from the DI mash ph of the malt and multiply by 35 e.g. if the malt has a DI mash pH of 5.7 and you want to mash at 5.4 you will need about 35*(5.7 - 5.4) = 10.5 mEq/kg of malt. This is pretty rough and why we do test mashes and use pH meters.

Ok so far five gallons I should add 2.6 mL?
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Old 01-03-2014, 09:35 PM   #12
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The best thing to do is add the 2.6 mL of acid to about 100 mL of water and then add that 100 mL in convenient amounts to the 5 gallons while checking the pH (lots of stirring, obviously). You would then sneak up on the desired mash pH. If you overshoot then just add more water until you get back on target. If you don't have a pH meter, get one (but apparently you do).

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Old 01-03-2014, 11:37 PM   #13
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The best thing to do is add the 2.6 mL of acid to about 100 mL of water and then add that 100 mL in convenient amounts to the 5 gallons while checking the pH (lots of stirring, obviously). You would then sneak up on the desired mash pH. If you overshoot then just add more water until you get back on target. If you don't have a pH meter, get one (but apparently you do).

Got it. Thanks for help!!
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Old 01-05-2014, 11:51 PM   #14
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I am confused again.

Can I just fill up my HLT with all my brewing water , stick my ph meter in there, and then add acid till it is at 5.4 and then use that for my strike and batch sparge water?

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Old 01-06-2014, 12:53 AM   #15
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I am confused again.

Can I just fill up my HLT with all my brewing water , stick my ph meter in there, and then add acid till it is at 5.4 and then use that for my strike and batch sparge water?
I don't think it's that easy but I'm interested to hear what aj or Martin have to say.
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Old 01-06-2014, 04:07 AM   #16
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Can I just fill up my HLT with all my brewing water , stick my ph meter in there, and then add acid till it is at 5.4 and then use that for my strike and batch sparge water?
Yes, you can do that but most people like to have an idea as to how much acid they will need before they start out so they send a sample off to the lab where the lab adds acid until pH 4.4 is reached. The amount used is the alkalinity and they report that to you. You don't want to go as far as 4.4 but only to 5.4 and so need to make an simple calculation or use the curves to determine how much acid you need to add for the total volume you are treating. You can add half of it, check pH, add half of what's left, check again and so on until you hit pH 5.4 or you can add it all and check and if your pH went lower than 4.4 add more water to bring it back up.
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Old 01-06-2014, 01:19 PM   #17
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I am confused again.

Can I just fill up my HLT with all my brewing water , stick my ph meter in there, and then add acid till it is at 5.4 and then use that for my strike and batch sparge water?
Yes, you can. But most who have tried this blindly, found that they overshoot the acid addition. Because of the interaction of pH and alkalinity, the water pH barely changes during the early acid additions (small) because the water's alkalinity is being consumed. The pH drops like a rock when the alkalinity is gone.

Therefore, having a good idea of the proper acid amount is a safer way to perform acid additions.
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Old 01-06-2014, 01:53 PM   #18
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I understand more. Thank you both for the help

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Old 01-06-2014, 02:24 PM   #19
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You can see what Martin is talking about by looking at the second curve in #7. We found, for the conditions of the OP, that we needed to change charge per mmol from -0.9 to -0.1 i.e. that we have to add 0.8 mEq/mmol acid. If you do it as I suggested above you add half the acid (0.4) that brings you to -0.9 + 0.4 = -0.5 on the left axis. Adding half of what remains, (.2) brings you to -0.3, half of what remains then, 0.1, to -0.2, then to -.15. If you look at the pH's corresponding to those levels of charge you will see that the amount of pH change for a given acid increment is large near pH 8.4, decreases around ph 6.38 (where bicarbonate's buffering peaks) and then becomes large again as the pH gets into mash pH range. Using 1/2 the remaining acid at each step compensates for this and you are less likely to overshoot.

For those readers who are thinking 'You'll never use all the acid if you only take half at each step' I offer the following old chestnut about the engineer and the mathematician who are brought into a room with a curtain at the far end and distance markings on the floor. The curtain is withdrawn to reveal two lovely young ladies wearing nothing they didn't come into the world with. The gents are instructed that they may move towards the ladies in discrete steps each of which halves the remaining distance to them. The mathematician bursts into tears of frustration for he knows that while the series 1/2, 1/4, 1/8.... does converge it takes an infinite number of steps for it to do so. The engineer smiles broadly for he knows that he can get to 'working distance' with a small number of steps (10 will take him 99.9% of the distance).

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Old 01-06-2014, 02:53 PM   #20
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So then I have a question about this...

The method described seems to deal with the buffering of the mash (grist) which has to be calculated or observed (test mash) to calculate the necessary acid/base addition, as well as titrating and diluting the total water bill to 5.4 pH. I assume the calculation of the grist acid addition (consider a negative value for alkaline requirement) is then added to acid required to A.) overcome the apparent alkalinity (carbonates and bicarbonates) and B.) dilute/acidify the total water volume to 5.4 pH (I assume at room temperatures as well).

It seems to me that we are adding unnecessary acid. Why acidify the sparge water portion to that extent as part of the whole water? If we acidify the whole volume to 5.4 and have the addition for the mash, then what happens when the volumes are divided for strike and sparge? It seems that the strike water will have a portion of the acid necessary to set the mash pH and the sparge will drive that pH further as it rinses the grains and ends up in the kettle.

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