View Full Version : Measure and adjust pH during primary?

11-30-2012, 08:01 PM
Hello all!

Sorry if this has been asked before, but:

I understand getting the pH in the right range before fermentation starts.

But, is it necessary to measure and adjust the pH level during active, primary fermentation?

Is it even possible to get an accurate measurement with the presence of so much CO2?


Chevette Girl
11-30-2012, 08:12 PM
You generally don't want to decrease the pH before fermentation, its tendency will be to drop as fermenttion progresses, however if the pH gets too low (too acidic) you may have to adjust it upwards to keep your yeasties healthy.

Medsen Fey
11-30-2012, 11:12 PM
Especially with traditional meads, the pH tends to drop during the first couple of days. It can be important to measure pH during fermentation so you can adjust it upward if needed. You never have to lower pH for fermentation, and usually you don't have to raise it prior to pitching yeast unless you are fermenting something really acidic like lemon juice.

The effect of CO2 usually will only drop the pH about 0.1 in most cases.

12-01-2012, 06:19 PM
Thanks to both of you for the quick replies. I have only ever added calcium carbonate to must before fermentation to make it less acidic and give it a bit of buffer capacity. I've never added acid, but then most of my work so far has been with traditional type meads using Red Star Champaign and Red Star Cote des Blancs both alone and in combination. Both work well starting at 4.0 and above. I have added additional calcium carbonate 24 - 36 hours in as there is a noticeable drop in pH at that time. Buffering up in advance seems to help the need for additions.

I read some threads on another site where posters said pH measurements during fermentation were not reliable due to the presence of carbonic acid (CO2). There seems to be some truth to this but I found scientific articles on fermentation documenting the need to keep the pH from falling to far and stressing the yeast. These posters were wine makers though....

I use a properly calibrated pH meter. Maybe the absolute readings are more acidic due to the dissolved and out gassing CO2, but a taking the readings as relative might help identify problems.

Does anyone else measure pH during fermentation or use any of these techniques?


Joe (Magneto)

Medsen Fey
12-01-2012, 09:04 PM
Traditional meads usually don't have much buffering capacity so you will typically see a huge pH drop during the first 48 hours or so. You can easily see drops from 5.5 to 3.2 or lower just as an example.

The main reason for this drop is the production of organic acids by the yeast. The dissolved CO2 plays a much smaller role. How can you be sure of that you ask? Test for yourself. Take a pH reading toward the end of fermentation while it is still fully saturated with CO2, then take a pH reading once the mead is completely de-gassed and still. You'll find the difference to be quite modest.