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Old 01-29-2013, 12:02 AM   #21
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Why such a thick mash at 1 qt/lb? With Kai's findings, I've moved to 1.5 qt/lb as my typical. Is your mash tun too small?
19lb of grain absorb 2.375 gallons. At 1.5qt/lb I am mashing with 7.125 gallons. First runoff is 4.75 gallons. For a pre-boil volume of 6.5 gallons (5.25 gallon final, 60 minute boil) that leaves only 1.75 gallons to do two batch sparges with. So mashing think is impractical, as my efficiency would suffer even more.
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Old 01-29-2013, 02:10 AM   #22
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I figured that the mash had to be thick. But regardless of the thickness I'm estimating a distilled water pH of 5.5. Even if the base malt would be a low pH base malt like Rahr (that one had DI water pH of 5.5 in my testing) the DI water pH of the grist would only fall to 5.3.

I think I have to run more experiments with grists high in dark malts.

But 4.7 is awfully low. It's not unlikely that there may have been an issue reading the strips. The 4.7 pH range is what I measured when I mashed only roasted malt. Since there is also base malt in this grist I would expect the mash pH to be at least in the 5s

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Old 01-29-2013, 04:26 AM   #23
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I tested twice, used my artist wife to help with the color. I had dipped in my mash paddle, let drips land on a clean cool glass plate, waiting a few minutes, then dipped the sample. At it 2 seconds then read it. Thia was after 15 minutes mashing. Could be the strips though. Would it be smart for me to add the dark grains later o reduce the pH hit? That is if what I read was real.

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Old 01-29-2013, 05:23 AM   #24
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let drips land on a clean cool glass plate, waiting a few minutes, then dipped the sample. At it 2 seconds then read it.
I don't think that is the proper procedure for using the strips. I think you should use at least a sample that is as much as a tsp to submerge the strips in it. The problem is that the strips themselves act as an acid and when there is too little sample the strips themselves may skew the results. It's hard to tell if this could have been the cause, though.

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Old 01-29-2013, 08:38 AM   #25
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That could have been part of the problem. I think however next batch I am going to do water adjustments usin the spreadsheets found and will do the larger sample with the pH strip. I suppose not having a "pure" sample isn't terribly necessary is I have the sheets to use as reference.

Is there a general rule for pH offset at mash temperatures? I plan to do at mash and at room temp to get the offset myself, but am a bit curious.

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Old 01-30-2013, 08:02 PM   #26
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This was a timely thread. I just ordered a replacement probe for my pH meter and plan on doing a small stove top test mash on my RIS recipe. If I undershoot my test mash by several points how much pickling lime would you suggest adding to the test mash (say 1.5# grain) or full mash (25#) with about 1.25qt/gal? I do have an accurate gram scale and I have the same water profile as the OP.

Edit: I should add that I plan on adding about 1g/gal of calcium chloride to my mash to get the calcium level up for the yeast.

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Old 01-30-2013, 08:38 PM   #27
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I guess I'd do it this way. Base malts seem to have a buffering capacity of 25 mEq/kg-pH so figure how much you want to raise the pH and multiply that times 25*the number of kg of malt you mashed to get the number of mEq you need. Pickling lime has an equivalent weight of 37 mg/mEq. Multiply that by the equivalent weight of pickling lime thus

wt_lime ~ Delta_pH*25*kg_malt*37

Example: You get mash pH 4.9. After waiting a few minutes to be sure it isn't increasing on its own (which it often does) you decide to raise to 4.4 i.e. by 0.5 pH. You mashed 10 kg of malt (22 lbs). The lime required would be 0.5*25*10*37 = 4625 mg. I'd start by adding 1/3 or one half that, stirring it in and checking pH. Then add another small portion of the total. You don't want to overshoot.

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Old 01-30-2013, 08:58 PM   #28
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A.J, you are forgetting about the PH lowering effect of the calcium that is in pickling lime

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Old 01-30-2013, 09:34 PM   #29
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A.J, you are forgetting about the PH lowering effect of the calcium that is in pickling lime
The pH lowering effect of the added calcium would be minor, but real. A better way for a brewer to assess and predict lime addition is with Bru'n Water. The pH lowering effect of the calcium and the pH raising effect of the hydroxide are incorporated.
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Old 01-30-2013, 09:46 PM   #30
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Quote:
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The pH lowering effect of the added calcium would be minor, but real. A better way for a brewer to assess and predict lime addition is with Bru'n Water. The pH lowering effect of the calcium and the pH raising effect of the hydroxide are incorporated.
An even better way is this: http://www.brewersfriend.com/mash-ch...er-calculator/

which makes a difference between the alkalinity derived from OH- vs. the alkalinity derived from bicarbonate. There is a difference.

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