[dolecek21]

Hey everyone,

While brewing today(vienna lager  ) I had a thought. I batch sparge using a cooler and typically take gravity readings for my 1st run, 2nd run, and pre-boil. Probably not all necessary, but I'm kinda that way it seems. I've never worried much about the pH in the sparge since it all gets mixed up and shouldn't have a chance to get too high while running off. In BeerSmith I have always looked at the runoff pH entry and been curious what it would be, but never tested. Well, today after pulling the sparge/2nd run for gravity I decided to go ahead and look at it. Sure enough, pH = 5.5 up from 5.35 in the mash. Not an issue.

This did get me thinking, however. Is there a decent relationship between gravity and pH for the sparge? My 2nd run/sparge gravity was 1.020 for this batch. It seems to make sense that as this gravity decreases, pH would increase, and there may be a point at which the gravity may be low enough to indicate a pH that is higher than desired, extracting tannins. This is more to satisfy curiosity than anything. I wouldn't expect to have this issue with a batch sparge unless you were making a very low gravity beer. Got me thinking though. What are peoples thoughts/experiences? Can you estimate a troubling pH simply from the gravity of the sparge?

[RC]

There is a pretty strong correlation between runoff gravity and runoff pH. Once the runoff gravity reaches about 1.008-ish, the pH approaches 6.0, which is about the pH where tannins really start getting extracted from the husks. This relationship is behind the rule of thumb to stop the runoff when its gravity reaches ~1.010.

[Robert]

Generally the buffer systems set up in the mash will hold the pH down right through the sparge in most circumstances we will encounter.  I do a conventional sparge, and with last runnings of just over 2°P the pH usually only rises by about 0.3 (because I know this I only occasionally actually track it.)  If you batch sparge, you should not have to worry.  It's really only a concern for the bigs looking to squeeze out every last penny's worth of sugar. As George Fix observed on this issue, "it is rare in brewing for efficiency and beer quality to be in harmony."  Here's to inefficiency.

[Brewtopalonian]

Hey everyone,

While brewing today(vienna lager  ) I had a thought. I batch sparge using a cooler and typically take gravity readings for my 1st run, 2nd run, and pre-boil. Probably not all necessary, but I'm kinda that way it seems. I've never worried much about the pH in the sparge since it all gets mixed up and shouldn't have a chance to get too high while running off. In BeerSmith I have always looked at the runoff pH entry and been curious what it would be, but never tested. Well, today after pulling the sparge/2nd run for gravity I decided to go ahead and look at it. Sure enough, pH = 5.5 up from 5.35 in the mash. Not an issue.

This did get me thinking, however. Is there a decent relationship between gravity and pH for the sparge? My 2nd run/sparge gravity was 1.020 for this batch. It seems to make sense that as this gravity decreases, pH would increase, and there may be a point at which the gravity may be low enough to indicate a pH that is higher than desired, extracting tannins. This is more to satisfy curiosity than anything. I wouldn't expect to have this issue with a batch sparge unless you were making a very low gravity beer. Got me thinking though. What are peoples thoughts/experiences? Can you estimate a troubling pH simply from the gravity of the sparge?

Excellent question!!!  I came here this morning looking for the answer to exactly this, and here I find you've posted it!  I have often wondered this myself.  But, what I'd like to know is what is more important in tracking your end of runnings gravity/pH?  Is it the pH or the Gravity that we should be watching closely?  I rarely have my end of runnings gravity below 1.010, but last week I brewed an Altbier and the end of runnings gravity was 1.008 before I was finished with the sparge, so out of fear of extracting tannins I stopped the sparge short and boiled a little less ( like .25gal less NBD).

I'd love to get the run down on this and why one is more important than the other if that is the case, and which one we should pay closer attention to?  Also, what is this I hear about an Iodine test?  I've never used it, but would like to learn more about it.  Thanks you brilliant brewers you!

Jared

[denny]

It's the pH that matters.  The gravity is just an indicator of that.

[RC]

In terms of extracting tannins, all you care about is the pH of the runnings. But since gravity and runoff pH are so closely correlated, tracking one means you are also tracking the other. So track whichever is easiest for you to track. If you're adventurous, track both pH and gravity for a few brews, and make a plot of pH vs. gravity. You'll see the close correlation, and this may also help you adjust for variances in your equipment or processes.

All that said, no one I know, me included, bothers tracking runoff pH or gravity. The only way I'd be still running off into the kettle when the gravity is near 1.010 is if I've made a big miscalculation with the recipe.

Iodine complexes with amylose, the main starch in malt. If amylose (i.e. unconverted starch) is present, the sample turns dark-purple/black. You can use this color change to check if conversion is complete or not. I consider this test pretty useless because, as long as you've created reasonably normal mash conditions, full conversion will always happen, I guarantee it.

[dmtaylor]

There is a pretty strong correlation between runoff gravity and runoff pH. Once the runoff gravity reaches about 1.008-ish, the pH approaches 6.0, which is about the pH where tannins really start getting extracted from the husks. This relationship is behind the rule of thumb to stop the runoff when its gravity reaches ~1.010.

This.  The numbers are inversely proportional, and you can use one to give you indication of the other.

In terms of extracting tannins, all you care about is the pH of the runnings. But since gravity and runoff pH are so closely correlated, tracking one means you are also tracking the other. So track whichever is easiest for you to track. If you're adventurous, track both pH and gravity for a few brews, and make a plot of pH vs. gravity. You'll see the close correlation, and this may also help you adjust for variances in your equipment or processes.

All that said, no one I know, me included, bothers tracking runoff pH or gravity. The only way I'd be still running off into the kettle when the gravity is near 1.010 is if I've made a big miscalculation with the recipe.

Iodine complexes with amylose, the main starch in malt. If amylose (i.e. unconverted starch) is present, the sample turns dark-purple/black. You can use this color change to check if conversion is complete or not. I consider this test pretty useless because, as long as you've created reasonably normal mash conditions, full conversion will always happen, I guarantee it.

+1 here too.

[Brewtopalonian]

Awesome.  Thanks for the info!  Denny, what type of calculations do you make to determine the amount of sparge water to use so you never get close to 1.010?  This is the disadvantage of using brewing software - I really too heavily on it's automated calculations without truly understanding what's going on.

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[denny]

Awesome.  Thanks for the info!  Denny, what type of calculations do you make to determine the amount of sparge water to use so you never get close to 1.010?  This is the disadvantage of using brewing software - I really too heavily on it's automated calculations without truly understanding what's going on.

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I batch sparge and don't worry about it.  If my mash pH is good, the sparge pH will be also.

[dmtaylor]

Awesome.  Thanks for the info!  Denny, what type of calculations do you make to determine the amount of sparge water to use so you never get close to 1.010?  This is the disadvantage of using brewing software - I really too heavily on it's automated calculations without truly understanding what's going on.

Sent from my XT1585 using Tapatalk

I batch sparge and don't worry about it.  If my mash pH is good, the sparge pH will be also.

Yup.  The only way you could approach 1.010 with a batch sparge is if brewing something with an intended OG less than about 1.035-1.040, which could happen for very few beer styles (Scottish 60/- and English mild, Berliner weiss, and that's pretty much it), in which case it's probably easier to just skip the sparge anyway and plan on no-sparge that day.