Temp control post-primary

It's summer time in southern China with temps suddenly in the mid-30Cs and expected only to get higher. The fridge in which I ferment can currently fit my 30l fermentor with enough space left for a shelf of beers. If I remove that shelf I might have enough space for a secondary, but it would be a squeeze. As such, I brew every 3 weeks (fermentor, then bottled) but would like to brew more. As I see it my options are either 1) squeeze a secondary into my fridge, 2) get another fridge, or 3) brew saisons. Actually the third isn't a realistic option because indoor ambient temps are already too hot and I'm not that big a fan of the style.

I've read, however, that a yeast's flavor profile is mostly decided during primary stage. Given that, how detrimental would it be to pull the fermentor from the fridge after primary? My only experience doing so is with a recent fruit beer. After two weeks in primary, kept at 18C, I racked the American ale base for the beer onto fruit, where it sat for another 2 weeks ... at around 27C! That beer is now bottled and a week from fully carbonating, but an early taste indicates it didn't suffer from the high temp in secondary.

Thoughts on post-primary higher temps, anyone?

It has been my experience that  - as you point out - the primary fermentation is the most critical in that the majority of the flavor profiles are derived during this phase. I have, on nearly every occasion, racked my brews into the secondary and located the secondary to a different place in my brewing area without much concern about temperature and my brews have always turned out great.  I have found that by the time the brew hits the secondary the yeast is mostly completed with its work and in the final stages of settling out. 

I've let beer sit in secondary for a couple months during the summer and it came out fine (Well, mostly. I'll get to that at the end of my post). Like you said, it's the temperature when it is fermenting that matters most.

On the other hand, temperature changes affect the pressure of the air in the head-space between the beer and the airlock. So I would recommend using the S-shaped locks. In the secondary there won't be enough fermentation to create enough positive pressure to counter pressure changes from temperature changes. If you use a traditional style of lock, liquid can get sucked back into the brew. Not so with an S-shaped one (assuming it isn't overfilled). When the temperature cools down, the pressure in that head space drops. If liquid gets sucked in when that happens, it can cause an infection, not to mention an empty airlock. I learned that one the hard way.

Thanks @Keller.

Thanks @Maine.

You've emboldened me to let my secondary sit at room temp. But I didn't think through the problem well enough. I've become a fan of cold crashing before bottling and I won't be able to do that if there's a primary fermentor in my fridge.  I think the solution is to find space in my brewery for a second, small fridge. Won't my missus be pleased!

Maine Homebrewer said:

On the other hand, temperature changes affect the pressure of the air in the head-space between the beer and the airlock. So I would recommend using the S-shaped locks. In the secondary there won't be enough fermentation to create enough positive pressure to counter pressure changes from temperature changes. If you use a traditional style of lock, liquid can get sucked back into the brew. Not so with an S-shaped one (assuming it isn't overfilled). When the temperature cools down, the pressure in that head space drops. If liquid gets sucked in when that happens, it can cause an infection, not to mention an empty airlock. I learned that one the hard way.

Click to expand...

If you don't want to buy an "S" style airlock and you normally use a 3 piece, what I do is fill my 3 piece with star san from my spray bottle. any liquid that has gotten sucked in wont cause an infection that way in my experience.

<i>any liquid that has gotten sucked in wont cause an infection that way in my experience.</i>

That is true, but then it could suck all the liquid through, leaving you with an empty airlock.

Racked to secondary today and it's sitting on my workbench slowly raising from 18C to room temp, 28C. I wrapped it in insulation to make the transition as slow as possible, but it's been dry-hopped and will sit where it is for the next two weeks -- it's sure to reach room temp soon enough. I left about zero headspace. My secondaries are all plastic big-mouth bottles that hold exactly 19l. It's affixed with an S-shape airlock and filled Starsan. I used to use vodka, but that got expensive.

With zero headspace, and because I dry hopped, my problem hasn't been sucking back into the fermentor, but bubbling out, with hops threatening to clog the airlock. I'm not worried about it. Just make sure nothing that gets out is allowed to get back in through the airlock hole!

Thanks again for everyone's help. Cheers!

interesting to see how mofo turns out. i have warmer temp here in Thailand, usually about 28-32 in my house this time of year.

i just moved a brew into a 19ltr drinking water bottle, filled right to the brim but no airlock. i just put the top on, tighten it and wind it back just a crack to leave the smallest of pressure escape path. i hope this works ok as it seems that after 6 days, its still fermenting a bit.

i keep it in a big ice box (esky in Australian) and every morning and evening i rotate in and out two 1.5L ice filled bottles. temp is holding steady between 19 and 22C which i think is good for ale and IPA.

if mofo's experiment with higher temp works out, i may try that. it will give me more space to start another brew

Update on my warm secondary fermentation experiment:

I've now sampled two different beers that sat in secondary for two weeks at a room temp of ~28C (82F). Both were beers I've brewed before but kept at proper ferment temps through to bottling, so I'll compare them with those previous brews.

Loquat Ale (American ale)
7.7% ABV  61 IBUs  15 EBC
This sat in primary for 10 days at 19C, then sat on the fruit at 28C for close to three weeks before bottling. Two weeks later it was fully carbed. I'd say taste-wise this beer is nearly identical to the loquat beer I brewed last spring (loquat is only available in April in So. China). This beer had only bittering hops and some light late-boil aromatic hops. The original recipe called for dry hopping but I of course planned on fruit instead. Compared with last year, the warmer secondary temp really brought the yeast back to life when the fruit was introduced. I think the higher temp might actually have been a benefit. This beer was tart in its first couple months last year before mellowing out. This year's batch is slightly less tart and I'm sure will mellow out same as last year's.
Verdict: Warm secondary certainly didn't hurt and might even have helped.

Pale ale
6.5% ABV  36 IBUs  14 EBC
I've brewed this half a dozen times. This was in primary for 7 days and secondary, again at ~28C, for 14 days. 10 days later it was near fully carbed. Taste-wise the malt character is identical to what it's been with past brews, but the hop profile seems to have been affected by the warmer secondary temp. This beer is dry hopped for 14 days with 28g Nelson Sauvin straight into the FV. The gooseberry fruit-juice quality is still on the palate, but the nose is slightly diminished from previous brews. I'm wondering too if the warmer secondary might affect stability, but this beer is never around long enough for that to be an issue.
Verdict: Will try warm secondary again but might also try increasing hops or using a hop-back before bottling.

I should add that I cold crash all my beers to 1C for at least three days before bottling. But when dialing in numbers for CO2 volumes I use the highest temp the beer reached during secondary (28C) to account for residual carbon dioxide. This has given me the same level of carbonation as previous brews, when the beers never got above 19C.

I have a wee heavy and a wit coming down the pike and can report on those, too.

Hope this helps anyone who, like me, is trying to free up fridge space in order to brew more often. Don't fear warm secondary temps!