View Full Version : Fermentation rate differs with batch size?

01-20-2012, 06:41 PM
I am making 3 batches of JAO. 2 are one gallon carboys and one 5 gallon batch in an Ale Pail. The 2 one gallon batches have different fruit combinations, (nectarines & blueberries in one and cherries & blueberries in the other), and the 5 gallon batch is straight JAO exactly by the recipe and scaled up. I started all three on 12/29/2011. As of today, 1/20/2012, the 2 gallon batches have slowed to 3.5 to 4 minutes per bubble. My 5 gallon batch is still fermenting at a 1 bubble every 11 seconds. Being that my Ale Pail is not clear, how would you recommend that I determine when it is cleared and ready to bottle? I was planning to bottle all 7 gallons when the 2 small batches cleared but that obviously isn't going to work out. Thank you all for the suggestions on my last posting and thanks in advance for your insight on this issue.


Chevette Girl
01-20-2012, 07:52 PM
Ok, I'll get the obvious comments out of the way first - airlock activity is a lousy way to track your fermentation, don't trust it. Trust your hydrometer. I've had all kinds of airlock activity and very little drop in SG, and I've had some where the SG dropped really fast without violent airlock activity.

And if there's blueberries and cherries and nectarines involved, you've made JAO variations, not JAO's, so it's to be expected because of the different nutritional contrubutions from the fruits that your fermentation rates might be different.

That said, I've started very similar batches concurrently and found with a 1-gal batch in a 3-gal bucket and a 5-gal batch in a 5-gal bucket, the smaller one with more headspace dropped its SG a lot faster than the big batch. I suspect in my case it's because more headspace made for better aeration.

As for the opaque fermentation bucket, I've done larger batches of JAO and variants in my bucket and you can tell when you open the top, when it's clear, you'll be able to see right to the bottom of the bucket if you either pop the lid off or pop out the airlock and look down the hole. Don't worry about oxidation at this point, JAO's and variants are really resistant. I find mine usually clear between one and three weeks before the fruit drops, when you can't see floating fruit anymore it's usually a good time to rack it or bottle (I prefer racking it a week or two before I bottle, makes sure I miss most of the sediment and gives anything I got anyways a chance to settle out). Every now and then I get a variation that refuses to clear, but this is what happens when you break the warranty by not following the recipe exactly ;D

01-21-2012, 06:10 AM
Rather than trying to circumvent the recipe with "planning to bottle all 7 gallons when the 2 small batches cleared", follow the recipe guidance and leave each batch until it's clear and the fruit has dropped i.e. usually about the 2 to 3 months in mark.......

That's what I'd go with.