Porter and carbonate levels

Hey everyone,

I'm venturing back into porter territory after a long hiatus due to dark malt astringency concerns. I brew all-grain with RO water plus gypsum, CaCl2 and lactic acid for pH control. I have great success with lighter beers, but the dark-dark brews have been a challenge.

Many online sources state high carbonate levels are beneficial for this style, but do I need it? Plugging my values into EZ Water I get a room-temp pH of 5.42 with 3g gypsum + 4g CaCl2 and no acid. It's a 4 gallon batch brewed in a 5 gal pot (requires a little water top-up in kettle or fermentor). My grain bill is:

3.65 lb (55%) MO
1.3 lb (20%) Pale Wheat
0.65 lb (10%) UK Brown
0.65 lb (10%) UK C80
0.35 lb (5%) UK Chocolate

My confusion lies in the knowledge that porter/stout cities like London and Dublin use high carbonate water with significant residual alkalinity, allowing high amounts of roast malt and preventing pH dropping too low. I know just enough here to be dangerous.

Is it beneficial to add carbonate (baking soda) and then adjust back down with 88% lactic acid, perhaps for increased stability, or should I skip the carbonate and go with low to no acid?

Thanks in advance.

...also, is brown malt considered roasted/toasted or a base grain? Mash pH estimates change drastically depending which category I choose and which calculator I use.

rhys333 said:

Many online sources state high carbonate levels are beneficial for this style, but do I need it?

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Probably not but one can never be absolutely certain. Also the old stuff still floating around was based on lack of understanding of carbonate chemstry. Brewing waters are often alkaline because of the presence of bicarbonate ion - not carbonate. You can't get alkalinity of 100 ppm as calcium carbonate simply by dumping 100 mg of calcium carbonate into each liter of water.

Furthermore, if the London brewery had water coming in at 100 ppm alkalinity that does not mean that the water that went into the mash tun had that level f alkalinity. Simply heating hard water often results in the precipitation of a good portion of the alkalinity.

rhys333 said:

Plugging my values into EZ Water I get a room-temp pH of 5.42 with 3g gypsum + 4g CaCl2 and no acid. It's a 4 gallon batch brewed in a 5 gal pot (requires a little water top-up in kettle or fermentor). My grain bill is:...

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That sounds about right. if I plug into a robust pH estimator I get slightly less but even though the estimator is robust the malt data that goes into it isn't. I have to make assumptions about your malts one way or another as do ll the programs. They don't use the same assumptions and that's why they all give different answers.

rhys333 said:

My confusion lies in the knowledge that porter/stout cities like London and Dublin use high carbonate water with significant residual alkalinity, allowing high amounts of roast malt and preventing pH dropping too low. I know just enough here to be dangerous.

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See above.

rhys333 said:

Is it beneficial to add carbonate (baking soda) and then adjust back down with 88% lactic acid, perhaps for increased stability, or should I skip the carbonate and go with low to no acid?

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No, it is absolutely not beneficial to increase proton deficit with alkali and then turn around and reduce it back with acid. Skip the carbonate and the acid and get the same proton deficit.

rhys333 said:

...also, is brown malt considered roasted/toasted or a base grain? Mash pH estimates change drastically depending which category I choose and which calculator I use.

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See comments above.

I'm glad you asked this question, as I'm prepping for a scottish ale and had a similar conundrum.

ajdelange said:

No, it is absolutely not beneficial to increase proton deficit with alkali and then turn around and reduce it back with acid. Skip the carbonate and the acid and get the same proton

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Thank you AJ. I appreciate the detailed explanation. I'll skip the baking soda then. I'm right that carbonate doesn't impact flavor in any way?

Also, any suggestions on if I should categorize Bairds brown malt as a roasted grain or base in EZ Water? I'm attaching a photo for reference.

View attachment 1440270080832.jpg

rhys333 said:

Thank you AJ. I appreciate the detailed explanation. I'll skip the baking soda then. I'm right that carbonate doesn't impact flavor in any way?

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If carbonate is improperly used it will not completely dissolve and will hold the pH of mash, wort and final beer high in which case I have heard reports of, unsurprisingly ebough, 'chalky' tasting beer. Gordon Stgrong speaks of alka-selzer' flavor. Properly used, i.e. to neutralize acidity that wouldn't be neutralized without it, the pH of mash, wort and beer will be proper. At proper beer pH most bicarbonate and carbonate is converted to CO2 gas. The bicarbonate that comes from 'carbonating' beer, at proper beer pH, is actually in higher concentration than the bicarbonate from carbonate/bicarbonate ions in the water.

rhys333 said:

Also, any suggestions on if I should categorize Bairds brown malt as a roasted grain or base in EZ Water? I'm attaching a photo for reference.

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As I've never measured the stuff I can't really say but the high color certainly suggests that it is more acid than base malt. Absent any other guidance I suppose I'd use the numbers that correspond to a caramel or crystal of about the same color.

I think that Brown Malt is kind of like an English version of Special Roast, in that it's a roast malt, but a very very pale one. What that means in terms of acid, I don't know, as I'm guessing it's one of those outlier malts that isn't modeled well.

Experience has taught me (because all the pH models are just that, models) to get my flavor ions where I want them, measure the pH, and then adjust with acid or baking soda from there.

Another thing you could consider, especially if you're going for a London style porter, is using some canning salt in place of some of the calcium chloride. Some sources have mentioned higher sodium being an integral part of the London porter style (how true that is objectively, I don't know), but my own personal experience (and preference) tends to agree. In mine, I go ~40ppm sulfate, ~60ppm sodium, and ~80ppm chloride. And it might help the pH from dropping too low, too.

Thanks again guys. I'll go with C60 then. Qhrumphf, if I was going to pick a specific water profile, it'd be Sam Smith well water, but with so little info out there other than "incredibly hard" I decided to go with ratios similar to yours. I recall growing up in Yorkshire the water was known as a high quality drinking water which must play a role making SS beers as tasty as they are. At some point I might try using the yorks profile as inspiration (even though the SS water is isolated and may differ slightly). All part of the fun though