pH problems

[Lawpaw]

I've been having very significant drops in Ph after my last nutrient addition at 1/3 sugar break. Until then the pH only drops slightly.

I just moved 2 one gallon mead batches to secondary. Both above 3.6 until after that last nutrient addition, then they jumped down to 2.9 and 3.2 in a couple of days. I added 1/2 teaspoon of K-bicarb and one read at 4.2 the next morning (I should have checked both, but assumed they would both be higher).

Tonight the 4.2 mead was back down to 3.7 and the other one was at 3.2.

Any reason these meads would keep moving down?

My best thought is that the 1/2 teaspoon of wine tanin I added to each batch is somehow binding with the carbonates in the water and dropping them out.

[Braxton]

I'm sure there is a much longer, more detailed explanation, but fermentation causes pH to drop. If you are watching the pH throughout, you should expect it to fall. Keeping it above 3.0 is ideal.

pH gets a bit weird because of the buffering capabilities of different meads. Using fruit in meads tends to result in less pH problems, because the mead will be able to buffer the drop in pH, seemingly keeping it at the same level. A traditional mead has less buffering capability and is more likely to run into problems.

I know there are some great posts on here about pH, perhaps one of the folks who has been around longer can direct you to them.

[Lawpaw]

Thanks for the overview. I have read the posts on pH drops, which is why I was monitoring.

But it seems like most people think that the pH drop occurs mostly in the first couple of days, then levels off. I seem to see the opposite, fairly level pH until sugar break, then a big drop.

[Medsen Fey]

It may vary depending on the honey and the buffering capacity present. Also, many fermentations reach the 1/3 sugar break by 48 hours so the speed of the fermentation will be a factor. The tannins don't bind the carbonates. The carbonates combine with free H+ (acid ions) and transform into water and CO2 which bubbles out. The nutrients used will also have and impact. DAP may actually cause the pH to drop lower. Autolyzed yeast usually bring the pH up a bit.

The variability in pH shifts is a reason why it pays to measure and follow the pH.

[Lawpaw]

Are you saying its mostly carbonic acid? If so, wouldn't pH rise after fermentation as it degasses.

I aerate heavily until 1/2 sugar break, then do little to degas. I suppose carbonic acid could effect things after that, but I never imagined it affecting pH much.

My mistake here was thinking the two meads would have similar pH movement.

[Medsen Fey]

It becomes carbonic acid when it bind up a free acid ion (H+) then transforms to CO2 and water. The net effect is to reduce the number of free H+ - that raise the pH.

[Lawpaw]

I was referring to CO2 from fermentation dissolved into the water. Does that affect pH?

[Medsen Fey]

CO2 produced during fermentation will be dissolved in and will create some carbonic acid and lower the pH. The effect may drop the pH by 0.1 or so, but usually not more than that.