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Old 02-28-2011, 08:12 PM   #21
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ajdelange,

For the PH/Temp meters I have seen some with a temperature range of 23 to 140 F (-5 to 60 C) sold at brewing supply sites. Are these of any use to a brewer? Won't I need something with at least ATC at or above 160F.
As has been noted you will want to take measurements at room temperature. There are several reasons for this:

1. Temperature cycling is stressful to the thin glass membrane which is the working part of your meter and will result in shortened electrode life.

2. Calibrating and measuring at the same or nearly the same temperature does not make much demand on the ATC system. This is good as while ATC does work at higher temperature its is a source of error unless the electrode is perfect. The smaller the temperature excursion the smaller this error.

3. True pH (i.e. the actual pH of the mash or wort) is dependent on temperature. The difference between a pH measured at protein rest temperature and a pH measured at sachharification temperature will largely be because of temperature difference. If the pH is measured at room temperature the real pH difference, if any can be observed even though neither measurement represents the true pH.

4. It is standard practice to take measurements at room temperature. In order to be able to compare pH values you obtain to those obtained by others you want to make your measurements the same way they do.
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Old 02-28-2011, 08:25 PM   #22
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Do you try and cool the sample or just let it naturally come down to room temp? Is time a factor? At what stage(s) of the mash are PH readings taken. The initial PH (from water to water with grain at a temp) will change until it gets to a stable level, right?

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Old 02-28-2011, 08:46 PM   #23
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Do you try and cool the sample or just let it naturally come down to room temp? Is time a factor?
I cool it down but dipping it out of the vessel in a little metal saucepan which I can then set in cold water. It's not so much that time is of the essence in getting an accurate reading as it is in getting the pH measurement out of the way so you can move on to the other things you need to be doing.

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At what stage(s) of the mash are PH readings taken.
That's really up to you. Certainly at dough in then every few minutes after that until the pH stops changing. This may take 20 minutes or longer. In addition to the mash readings I take them at the conclusion of every decoction, going in to the kettle and in the fermenter. Then in the fermenter until the pH stops droppin (once a day for this) and then in the finished beer. That's a lot and you may not wish to do so many readings but each of those readings is like a milepost at which you can compare to the results you obtained at that point in other brews - the same style or not.

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The initial PH (from water to water with grain at a temp) will change until it gets to a stable level, right?
Unless you want to keep track of how your water varies over time it is not necessary to know the water pH.

When controlling mash pH by mineral addition, the mash pH will lower over time. When controlling with sauermalz it will increase. In either case you will want to take measurements until the reading is stable. This is not to be confused with the time it takes the meter to stabilize in an individual reading. That may be a minute. The changes I am talking about here occur over 20 minutes or more.
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Old 02-28-2011, 09:04 PM   #24
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Do you try and modify at fermentation or is this just for record?

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Old 02-28-2011, 09:05 PM   #25
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AJ, I think that Kai conducted some experiments and found that the mash pH was fairly stable within 15 minutes.

I expect that a lion's share of the pH change will occur by 5 minutes and the remaining change will diminish with time asymptotically. I think that an early sample after 5 minutes and then a sample after 15 minutes should be sufficient.

I agree that taking a small sample and placing it in a small container that can be externally cooled is the best way to bring the sample to room temp. I use a shot glass, but metal transmits heat better than glass. If you pre-cool the shot glass, you have the advantage of all that thermal mass to help with the sample cooling. Just a thought.

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Old 02-28-2011, 09:14 PM   #26
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When controlling mash pH by mineral addition, the mash pH will lower over time. When controlling with sauermalz it will increase. In either case you will want to take measurements until the reading is stable. This is not to be confused with the time it takes the meter to stabilize in an individual reading. That may be a minute. The changes I am talking about here occur over 20 minutes or more.
I'm a little confused here I thought sauermalz would lower pH, and that you would use it to control pH in lighter color beers where you didn't want to add more minerals.
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Old 02-28-2011, 09:20 PM   #27
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I've found that the pH does level off pretty quickly when relying on minerals to set pH. I've also found a slight decrease after each decoction. Conversely, with sauermalz it seems to take longer and there is a slight increase with each returned decoction.

When using sauermalz the acid from the surface is quickly dissolved and the pH plummets. You look at the first reading and say "Omigosh - I overshot!" but after a few minutes as the acid gets into the grain and the grain components dissolve things come to equilibrium and the pH levels off at a more reasonable level. So with sauemalz at least it is important not to panic and reach for the bicarb (for your stomach or the mash) but wait a while to see if pH is going where you want it to.

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Old 02-28-2011, 09:40 PM   #28
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OK thanks, I understand that. I guess I should have re read your post as you were talking about the time it takes the reading to stabilize.

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Old 02-28-2011, 11:15 PM   #29
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Do you try and modify at fermentation or is this just for record?
The main reason I do this is because a pH drop over the course of he first few hours is an early clue that the fermentation is going well. You'll see this before you see any foam or detect any gas evolution. No, I have never made tried to make an adjustment. If you don't see the pH drop, then you might as well accept that the beer is not going to work out. If there's no drop it means (given that you have oxygenated properly) that there is a problem with the yeast. Beers I have "saved" by pitching more yeast have wound up as dumpers.
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Old 03-01-2011, 02:49 AM   #30
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The main reason I do this is because a pH drop over the course of he first few hours is an early clue that the fermentation is going well. You'll see this before you see any foam or detect any gas evolution.
Will different beer styles (light, dark, Lager, Ale) have different PH profiles as they move into fermentation or do they all progress about the same?
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