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Home Brew Forums > Home Brewing Beer > Brew Science > pH differences: Bru'n water and actual.
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Old 08-08-2011, 06:39 PM   #1
el_loco
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Default pH differences: Bru'n water and actual.

Last batch was a blonde ale: 2 row, cara-pils, crystal 10 and Vienna. Added some gypsum, Epsom and cal-clor and a camden per water volume. After entering the grainbill and water additions, Bru'n said I'd be at a projected mash pH of 5.3. I entered my water pH of 8.0, which is what Ward labs reported. When I tested my mash at room temp with a calibrated pH meter I was at 5.6. Trying to determine where the inconsistency lies so that I may get a better understanding of how to adjust for proper mash pH.
My total hardness was 138, alkalinity 23, RA -13. Any thoughts,?

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Old 08-08-2011, 07:26 PM   #2
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I find that the spreadsheets tend to underestimate mash pH relative to what I observe in my own brewing (and hence wind up recommending addition of alkali where it is not needed) by about the amount you have noted. But others find them good to ± 0.1 or 0.2 pH. I believe the cause of this to lie in the modeling of the malts. Malt acidities are, I believe, more variable than they would need to be in order for the spreadsheet models to be as accurate as we would all like. For example, Weyermann's pilsner malt seems to have a di pH of about 5.75 whereas different maltsters Maris Otter offerings have DI water pH's of from 5.6 to 5.7. AFAIK the spreadsheets don't ask about or incorporate base malt DI pH info. And, I believe, that there is even more variability among different lots of the "same" (e.g. 60L crystal) malts from various manufacturers. I don't, thus, believe that mash pH can be predicted very accurately other than by experience and thus don't have a mash pH model in my spreadsheet.

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Old 08-08-2011, 07:37 PM   #3
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Malted grains are incredibly complicated chemical mixtures. I went through a stage of trying to quantify the process, chemically. I thought, incorrectly, that because I have an engineering degree and years of lab etiquette behind me it would be a fairly straightforward procedure.

Turns out There's a reason major breweries keep chemists on hand. Things like precipitation, temperature trend, and whether or not volcanoes are erupting in iceland all affect the chemical profile of the base grain even before it's malted.

Malting only ups the complexity. I opted to focus on more traditional technique and I think my brews have, if anything, improved. These days, instead of predicting how the brew will develop from first principles, I aim to be ready with an appropriate tweak for anything, should it become necessary.

Not trying to tell you what to do, only mentioning you're not the only one that's had issues cracking the "beer under lab conditions" nut. Best of luck, and, if you do find the algorithm, please post

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Old 08-08-2011, 08:07 PM   #4
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If one has the titration curve for each batch of each type of malt from each maltster and models that titration curve by, say, 10 pK's, then one ought, knowing the amounts of each malt in the grist and the water properties, be able to estimate the pH of a mash made with those malts and that water. The math would be cumbersome but doable. What wouldn't be doable is collecting all the titration curve data.

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Old 08-09-2011, 01:34 PM   #5
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This issue I ran into frequently when I was still trying for rigor was sample standard variation, both in the grist and the local water.

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Old 08-09-2011, 03:46 PM   #6
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Certainly the biggest player in mash pH WRT the water is it's alkalinity with hardness being in second place with the influence of alkalinity being 3.5 times that of hardness. Depending on your water source alkalinity (and hardness) can fluctuate appreciably over season or even shorter periods especially where a municipality draws water from several sources and blends them.

Alkalinity and hardness are very easy to measure but few home brewers do it. Thus the brewer could check the critical water parameters for every brew and thus remove the uncertainty that derives from use of a Ward Lab's report taken in June 2 years back with a brew being done in December of this year. Or the uncertainty can be removed by using RO or DI water and adding known amounts of hardness and/or alkalinity.

Even if this is done one is left with the uncertainty in the malt models and I think that's where the fundamental limitation lies. Although, as noted in the earlier post, I think I know how to predict mash pH accurately there is nothing that would motivate me to run a titration curve on each malt I intend to use in a particular brew and stick them into the model. I have a pretty good idea where pH is going to fall based on experience brewing the beers I brew with the water I use. It's been a long time since I had to make a pH adjustment in the mash tun. Were I to brew an entirely new style I would probably consider a test mash as that requires a single pH measurement and no modeling.

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Old 08-09-2011, 04:38 PM   #7
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Quote:
Originally Posted by ajdelange View Post
... AFAIK the spreadsheets don't ask about or incorporate base malt DI pH info...
Have you seen EZ 3.0 yet?

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Even if this is done one is left with the uncertainty in the malt models and I think that's where the fundamental limitation lies.
Yes, certainly a limitation, but I think the spreadsheets are getting to the point where one can get in the ball park wrt mash pH. And now with EZ3.0 you can even tweak the distilled water mash ph's of the malts if you have reason to. I would be curious if you were to plug in some of your past brews to see how close you would be.

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Although, as noted in the earlier post, I think I know how to predict mash pH accurately there is nothing that would motivate me to run a titration curve on each malt I intend to use in a particular brew and stick them into the model. I have a pretty good idea where pH is going to fall based on experience brewing the beers I brew with the water I use. It's been a long time since I had to make a pH adjustment in the mash tun. Were I to brew an entirely new style I would probably consider a test mash as that requires a single pH measurement and no modeling.
Yep, experimental data is where its at . Now if I could just capture "AJ's gut instinct" and get that into a spreadsheet somehow .
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Old 08-09-2011, 05:04 PM   #8
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Have you seen EZ 3.0 yet?
No, but I just had a look and I think that's a big step in the right direction.

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I would be curious if you were to plug in some of your past brews to see how close you would be.
I will do that.



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Yep, experimental data is where its at . Now if I could just capture "AJ's gut instinct" and get that into a spreadsheet somehow .
Brew a lot and drink a lot and it will come to you (at least the gut will).
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Old 08-09-2011, 09:30 PM   #9
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I believe the base malt has a lot to do with the mash pH.

I used RO water and only CaCl and CaSO4 and my last 3 batches (SRM-7, 10, 32) came in at 5.3, 5.3, 5.2.

I questioned the recommended use of acid malt in every batch, as I clearly don't need it with my Rahr pale ale malt. Some people, however, do need it to get their pH into range as I've seen in several posts on here.

So, what I take from this is that Rahr Pale Ale is more acidic than other malts.

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Old 08-09-2011, 09:46 PM   #10
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Yes, and that's why it is so important to know the base malt DI mash pH when estimating mash tun pH. Alkalinity at 60 ppm as CaCO3 will raise mash pH about 0.1 pH (relative to a base malt DI water mash) and 210 ppm as CaCO3 (84 mg/L as the ion) calcium hardness will lower it by the same amount but to know where you are going to wind up you must know where you are starting from. If your base malt DI pH is 5.75 and you have 210 ppm Ca hardness and use 3% acidulated malt your estimated pH is 5.75 - 0.1 - 0.3 = 5.35 i.e just about right but if you base malt DI pH is 5.6 you wind up with 5.6 - 0.1 - 0.3 or about 5.2 - getting a bit low.

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