Dry Hop Explosion due to cold temps? (PICS)

[alphakry]

I brewed a 1BBL IPA and split it into 2x 15 gallon fermenters.

I fermented both for 3 days with a blow off cane before capping them off with a PRV and finishing under pressure.
Total ferment for both (using US-05) was 8 days at 68F and then raised to 71F for an additional 2 days

On day 11, I dropped the temp of one to 55F while dropping the other back to 68F.

I added 8oz of hops to each... when adding to the 68F fermenter, there was evidence of increased activity and CO2 blow off but nothing out of what I expected.
However when adding the dry hops to the 55F fermenter... the activity that kicked up was INSANE. As the headspace filled with foam and hops, the PRV clogged - so I had to be quick about throwing a blow-off cane on to help ensure the pressure wasn't about to pop my fermenter. As you can see... in the time it took to replace a blank TC cap with the blow-off cane... it made quite a mess. Bye Bye dry hops!

Any ideas what gives? Both of these fermenters were treated the same. The intent was to compare the end result of dry hopping at fermentation temp vs cold temp, all while under pressure. But I did NOT have much luck with this experiment!

 

[Deadalus]

It might be supersaturation of CO2. The situation reminded me of superheating of water in a microwave. Back when I was a student, I used to heat my tea water in the microwave at school. I wasn't familiar with the microwave and would put the water in for maybe 1.5-2 minutes. I'd put the teabag in and the water would start bubbling. Not every time but sometimes quite vigorously. I tried explaining the phenomenon to the other grad students and they thought I was nuts. It's actually a real phenomenon were the vapor bubbles don't break the surface and the water doesn't appear to boil but can when disturbed. Anyway, not quite your answer but it did lead to another topic, supersaturation which I was a little familiar with. So I googled supersaturation CO2 beer and of course it lead me back to HBT to this thread which is short. But it could be supersaturation. Perhaps the colder beer was more highly charged with CO2 that hadn't escaped.

There's also that mead issue when adding nutrients but I don't know if that is the same.

You have pictures so at least people will believe you! No cell phone back then for me.

 

[IslandLizard]

Wow!
I reckon the beer in your 55F fermenter was more carbonated (containing more dissolved CO2), that all came out of solution when you introduced an abundance of nucleation sites by means of adding the dry hops.

 

[alphakry]

You know what... Now that you mention it, that second fermenter was actually reading a bit higher on the gauge when it was fermenting under pressure.

I wrote it off as possibly the oil gauge needing to be vented and recalibrated but you could be completely right that it actually experienced a higher carbonation and maybe even the suggested super saturation!

Bummer!!! Comparison fail! I may need to change my methods and quit pressure fermenting for a bit.

Thank you both for answers that seem more obvious now than they did at the time (during which I was still scraping hops off my wall...)

 

[Deadalus]

I'm not familiar with the ins and outs of the equipment you are using but I think you have a way to set the pressure as well as some sort of emergency PRV? CO2 is produced in excess so if both were set at the same value then probably the headspace inside would equalize...if they were both venting CO2 after you closed them. You did say you fermented three days with the blow off tube, so they may have been close to done and then I am not sure how much CO2 would be produced after that. Take an extreme value such as 100 psi. Maybe not enough fermentables left to produce enough CO2 to reach 100 psi. Slightly different wort volumes or multiple other factors might produce some inequality in the amount of CO2 produced. Even the best controls on a process will produce products with some variation. One might have had a little more than the other (or possibly a lot). However one was colder than the other and the cold one couldn't hold as much CO2 under regular saturation. If you look at a forced carbonation chart, 68F is not on the chart, but look at a 13 degree difference in temperature, say 47F vs 60F. At 0 gauge pressure there is a difference of 0.24 volumes. The difference increases as the pressure increases as well. If both were supersaturated (roughly equally), the cold one would diffuse(?) more CO2 as it doesn't hold onto as much in solution at the colder temperature.

Was the dry hopping done with the fermenter open to the atmosphere or do you have some sort of injection device to do it closed? Opening the fermenter itself would allow CO2 to diffuse and wouldn't necessarily need the beer to be supersaturated. A colder beer would lose more CO2 than a warmer beer when dropping from say 10psi to 0psi. The CO2 would normally need some time to diffuse if you opened it up but tossing in the hops could have sped that up quite a bit!

Just some thoughts not necessarily correct!

 

[rburrelli]

I have dry hopped at temperatures much colder than that (35 degrees) and never had that happen. Interesting.

 

[hotbeer]

SG's of both are still about the same?

 

[Rob2010SS]

You see videos like this all over social media of this happening to commercial breweries on much larger tanks and I’ve always wondered what caused that.