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Old 02-18-2013, 06:29 PM   #1
kenlenard
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Default What are the effects of a low mash pH?

I was having a conversation with some IPA brewers who said they like to get their sulfate levels into the 250-350ppm levels. I asked if they were adding gypsum to the kettle and some were but others said, "No, just the mash and sparge water". I asked how on Earth their pH could be lined up in the ideal range with all that gypsum in the water and one said, "I don't worry about low mash pH". This is an experienced and long-time brewer so I am wondering about this. High mash pH can cause harshness, the pulling of tannins from the grains, haziness, a darker wort, etc. What does LOW mash pH do for you?

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Old 02-18-2013, 08:27 PM   #2
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Calcium doesn't move pH that much. At 350 ppm with 0 alkalinity knockout pH is only shifted, per Kolbach's rule of thumb, by -0.17 pH so if your brewers don't use acid and don't use a lot of dark crystal then the pH shouldn't fall below the nominal desired range.

As for what would happen if it did: some speak of all manner of dire consequences. Some say they brew with those pH's all the time without negative consequences. I can't say as I've never been there.

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Old 02-18-2013, 09:39 PM   #3
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Interesting. I used my local water in EZ_Water and added enough CaCl and CaSO4 to the mash to get to 350ppm of sulfate and my RA was something like -300 and the pH was suitable for beers between zero SRM and zero SRM. This leads me to the idea that the pH would be ultra low. And... what if the beer being made was a darker IPA... say SRM 15 to 20 or something?

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Old 02-19-2013, 12:31 AM   #4
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I don't know how much CaCl2 you might have added in addition to the gypsum but the amount of calcium from gypsum that goes with 350 mg/L sulfate will lower the RA to -100 in the absence of any alkalinity.

Color of the beer doesn't really have much if anything to do with it (though many apparently still think it does).

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Old 02-19-2013, 11:58 AM   #5
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Quote:
Originally Posted by ajdelange View Post
Color of the beer doesn't really have much if anything to do with it (though many apparently still think it does).
Sorry AJ, can you expand on that? The color doesn't have much to do with the RA or mineral content... not sure what you were referring to. Cheers & thanks.
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Old 02-19-2013, 01:33 PM   #6
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We all know that Pilsner beer originated in a place where the water is low in mineral content (low RA), that Dunkles is brewed in a place where the water is high in mineral content, particularly bicarbonate, so the RA is high, that pale ales are brewed with high mineral water but with (relatively) low bicarbonate implying low RA etc. This caused John Palmer to conclude some years back that RA and beer color were correlated which conclusion he verified by plotting the colors of beer vs the characteristics of the water they were brewed with and fitting a curve to the data. He then published first nomographs (bak cover of his book) and then spreadsheets which could be used to 'design' brewing water based on color using this correlation. Home brewers loved this. It seemed there was a simple way to deal with this water chemistry business after all and led people to make statements like the one you did in #3 where you say "...my RA was something like -300 and the pH was suitable for beers between zero SRM and zero SRM". Calculators and spreadsheets based on this model were released by other authors and this model became quite prevalent.

There were several problems with his approach
1. As he didn't know what the actual colors of most of the beers were he generated color data from what he could find out about the grain bills.
2. Much of the published water data is bad
3. Even if one knows what the water chemistry in a region is one does not know what the chemistry going into the mash tun is.
4. The 'fit' wasn't very good.

With respect to the last point, if you look at a curve fit with r = 0.66 you might conclude that it is a pretty fair fit but in fact only 43% of the variation comes from the model. Fifty seven percent is 'noise'.

The result of all this was that a generation of brewers were blithly adding tablespoonsfull of chalk to their mash without ever stopping to think that this might be excessive.

Recognition of the problems has caused several spreadsheet authors to 'tone down' their residual alkalinity recommendations and so the situation is a little better but most who understand how things really work have dropped beer color as a 'design parameter' for beer and the idea of an 'RA requirement' to match a particular color seems to be fading.

There is, of course, a correlation between malt color and the amount of acid it produces and this can be used to help calculate predicted mash pH to the extent that this correlation is tighter (r closer to 1).

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Old 02-19-2013, 02:00 PM   #7
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Well, I know that homebrewers are looking for a tool (or tools) that will help them with this and I admit to liking the idea of getting the mash and water profiles for various styles correct and anything that will help the masses is good. Of course, it's not good if the product doesn't work, the information is misleading, incomplete or inaccurate. If you say that many of the spreadsheets are causing problems or just not filling in all the blanks, I would feel like I needed to look elsewhere for this. Another brewer recently said to me, "I'm trying to make good beer, not balance numbers on a spreadsheet" and I said, "But balancing numbers on a spreadsheet could result in making good beer!". Maybe I was wrong.

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Old 02-19-2013, 02:26 PM   #8
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Be careful or you'll get me started on a long discourse on modeling. A spreadsheet represents a model. Some models are better than others but none are any good if you don't put the right data into them. For example, I believe I know how to predict/control mash pH quite closely because I have a pretty good model. But I can't get the data I need to go into that model without doing a lot of hard, dull, repetitive work in the lab. This doesn't mean the model doesn't have value. I can use it to tell me about where mash pH will wind up and about how much acid I need to get it there but I'll use a fraction of the acid and check pH in the mashtun before I add it all.

I got a good perspective on modelling from a internet weather report prior to the big recent snow storm. The meteorologist said snowfall would be between 1 and 23". The eye candy asked why the range was so broad. The meteorologist said that whereas only a few years ago we had but two predictive models to choose from there were now 9. The least pessimistic model predicted 1", the most pessimistic, 23". The actual snow fall reached 30" in some places.

People are such suckers for anything that comes out of a computer.

Consider the following scenario. You are a young researcher with a family to feed working at an eastern liberal (tautology) university on long term climate models using government funding. Your model shows that increasing solar constant is a larger factor in long term warming that anthropogenic CO2. Maybe you should review your model.

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Old 02-19-2013, 03:01 PM   #9
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I get that. The products are only as good as the data and even then they should be used as a tool, not a magic bullet. I feel like the spreadsheets do an okay job determining (at least) the zip code of where the mash pH will be. The small adjustments can be done later with acid or whatever. But there is always a swirling vortex of information as it relates to mineral additions (mash, sparge, kettle), level of minerals in any given beer, water and the role it plays, etc. I keep thinking that I may have made better beer before I got into any of this. But I also keep thinking that I will make EVEN BETTER beer if I can get a handle on all of these pieces. I kind of feel like I have all the pieces of the puzzle but I haven't put the puzzle together yet. The results of many of the latest things I have picked up are now sitting in primary and secondary so fingers are crossed that some recent changes will create some better results.

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Old 02-19-2013, 03:15 PM   #10
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Quote:
Originally Posted by ajdelange View Post
As for what would happen if it did: some speak of all manner of dire consequences. Some say they brew with those pH's all the time without negative consequences. I can't say as I've never been there.
Establish that everyone is using the same protocol for pH testing and then do a beer swap?
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