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Home Brew Forums > Home Brewing Beer > Brew Science > Mash thickness as a pH adjustment
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Old 01-16-2014, 08:31 PM   #1
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Default Mash thickness as a pH adjustment

Hi,

Am planning an upcoming pilsner. I have pretty low alkalinity water (37ppm) and it looks like I may have to add some acid when I brew.

If I use a thinner mash, according to the spreadsheet, I still may have to acidify but probably have to use less acid. I'm assuming this is because I'm adding more bicarbonate ions with the larger volume of mash water.

My question is, why don't I read about using mash thickness as one of the knobs to adjust pH?

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Old 01-16-2014, 08:44 PM   #2
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Originally Posted by BackAlley View Post
Hi,

Am planning an upcoming pilsner. I have pretty low alkalinity water (37ppm) and it looks like I may have to add some acid when I brew.

If I use a thinner mash, according to the spreadsheet, I still may have to acidify but probably have to use less acid. I'm assuming this is because I'm adding more bicarbonate ions with the larger volume of mash water.

My question is, why don't I read about using mash thickness as one of the knobs to adjust pH?
Actually, forget everything I wrote, I goofed the spreadsheet up....again.
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Old 01-16-2014, 09:19 PM   #3
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It depends on the spreadsheet you are using (i.e. on how accurately it models bicarbonate chemistry). The bicarbonate (and carbonate) if any contribute to the proton deficit of the water. The lower the proton deficit of the water the fewer protons are needed from other mash materials and the lower the pH will be. If you have a water with total proton deficit of 100 mEq and mash grains + acid with a total proton deficit of -100 mEq at some pH things balance at that pH and it is the mash pH. If you now increase the water quantity by 10% you are adding 10% more proton deficit for the water (you now have 110). Proton deficit decreases as pH increases. The pH will thus shift higher reducing the water proton deficit to something less than +110 and decreasing the proton deficit of the acid + grains to something less than -100 (e.g. + 105 and - 105 so again you have balance). Thus adding water that is alkaline increases mash pH. If the alkalinity is low the shift will be small. There is also buffer 'dilution effect'. Without going into detail it should be clear that a pH 5.4 mash diluted infinitely with pure water will have a pH of 7.

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Old 01-17-2014, 01:56 AM   #4
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. . . diluted infinitely with water will have a pH of 7.
Are we to assume DI water here AJ?
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Old 01-17-2014, 03:17 AM   #5
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Originally Posted by BackAlley View Post
Hi,

Am planning an upcoming pilsner. I have pretty low alkalinity water (37ppm) and it looks like I may have to add some acid when I brew.

If I use a thinner mash, according to the spreadsheet, I still may have to acidify but probably have to use less acid. I'm assuming this is because I'm adding more bicarbonate ions with the larger volume of mash water.

My question is, why don't I read about using mash thickness as one of the knobs to adjust pH?
I have found with my pilsners and light Belgians that replacing 1/4 pound of pilsner malt with 1/4 pound acidulated malt works wonders. I do start with RO water.
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Old 01-17-2014, 05:22 AM   #6
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Are we to assume DI water here AJ?
Yes. I changed it to say 'pure water'.
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Old 01-17-2014, 05:24 AM   #7
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I have found with my pilsners and light Belgians that replacing 1/4 pound of pilsner malt with 1/4 pound acidulated malt works wonders. I do start with RO water.
Yes, 2-3% of your grist should be sauermalz for a Pils when starting from RO.
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Old 01-18-2014, 12:22 AM   #8
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Great topic, I've been starting to kick the idea around in my head as well. Whenever I use a thinner mash, I notice my PH go down seemingly proportionally. Today I mashed a 2.5 SRM Pils pretty thin, used very little gypsum for calcium and hit PH almost too low (5.1). My water alkalinity resembles the OP's.

The wort was beautiful. It is said that wort profile will change based on mash consistency (I don't have any science behind it myself), but the proof will be in the end product. If the beer turns out (I suspect it will), I will use this technique as a rule.

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