Does shape of fermenter dictate fermatation speed?

[bigtoe]

Brewed two very similar beers, same recipe with just hop changes to adjust bittering. Pitched 200ml of Notty washed yeast slurry into both of them from the same batch. Brew 1 was in conical fastfermenter, brew 2 in a youngs fermenter, both sealed 100% and both using airlocks. OG on both was 1.038, hoping brew 2 will brew down to the same 1.007 as brew 1.

Brew 1 fermented 100% out in 72hrs
Brew 2 is still going 4 days in so 96hrs and counting

Both were fermented at around the same 19 to 20C.

Does the shape of the fermenter make a difference?

[Dennis King]

Are they both plastic and are you using a fermenting fridge. Several months ago I switched to a stainless fermenter and still use the same fridge and controller. With the old plastic fermenter the temperature of the wort was always spot on with the controller. The stainless is always 1c below what the controller says.

[bigtoe]

Both plastic but not in a brew fridge, however they are in a semi controlled environment. The room I ferment in is held at 18c.

Thats pretty much why I got thinking fermenter shape is the only difference.

[WalesAles]

bt,
Are they both in the same part of the room?
Have you got a cold spot in the room?
Can you guarantee 18deg throughout the room?

WA

[gobuchul]

What about the mash times and temperatures?

Did you mash them separately?

If you did them on the same day, was the mash tun was a bit warmer from the first one than the second?

You may have the same OG with less fermentable sugars in the 2nd batch than the 1st?

Did the 1st batch oxygenate better when transferred to the conical FV than with the other? Higher oxygen level, more efficient fermentation?

[bigtoe]

Same recipe but different Hop additions.

Same OG, same mash schedule, same yeast, cooled to same final temp (within 0.5c at least) brewed on different days however but similar daytime temperature.

So it boils down to oxygenation possibly, both brews were dropped into the fermenters from a reasonable height, no further mixing was was carried out, both brews had 3 to 4 inches of foam in the fermenters by the time the transfer had finished.

2nd brew is still chugging along, may take a peak and gravity today, see if its dropped below what they 1st brew was totally finished at.

[rpt]

FV shape can affect how fermentation goes but whether it's significant on a homebrew scale I don't know. But you are trying to compare two separate brews so you'll have to do it again and report back.

[kev93_10]

Since I moved to a conical I've had my beers dry out WAY more and now if I'm surprised if it doesn't go below 1010.

K


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[bigtoe]

Well imo the conicals ferment quicker and to a lower gravity (dry out more) tested a little more now and found the conicals with notty yeast were dropping down as low as 1006, in the flat bottom fermenters 1010.

[steveshep8676]

I have two twenty gallon stainless steel conical fermenters which are double lined insulated with a glycol cooling coil in contact with the inner layer of stainless. In my opinion they are the best thing for brewing beer.
One of the selling points of conical tanks was that a brewer could use them for both fermentation and conditioning once the yeast had dropped. We rarely see that today, as most small breweries use separate conditioning tanks, but this is one of the selling points now associated with the homebrew versions of conical tanks. The most interesting aspect of these fermentors is their geometry. The more vertical the fermentor, the faster the fermentation. The fluid dynamics of the cone create CO2 bubble movement from the bottom of the cone up through the center of the tank. The taller the tank, the larger the bubble formed as it reaches for the surface. The movement of CO2 helps carry the beer to the top, where it migrates downward again along the sides of the fermentor. The position of the cooling jackets can even enhance this effect and can affect the fermentation rate.
Most commercial breweries now use conical fermentors and control their temperature with cooling jackets filled with glycol or another fluid. They monitor fermentation temperature at one or more points in the fermentor, and they regulate the flow of coolant to maintain the desired temperature. The thermowell is either built as part of the fermentor or is inserted through a triclamp fitting into the beer. You place the probe from the controller inside the thermowell, and it accurately measures the temperature of the beer.
Tanks can have multiple jackets, providing more capacity and the ability to control different portions of the fermentor at will. It is particularly important to have the cone jacketed, as the yeast will spend time in the cone when settling. The ability to control the jackets at different temperatures can be advantageous. For example, with a separate temperature setting for the cone, the brewer can cool the cone before dropping the fermentation temperature of the tank. This encourages flocculation and ensures the cone is cold enough to keep the yeast from building up too much heat as it sits in the cone until harvested. I attach a glass vile yeast collector to the bottom of my conical which has valves at both ends so the yeast I capture is the best creamy white yeast with no trub, perfect for repitching. There's a 2" butterfly valve on the bottom of the cone to dump trub with so a large valve there's never any chance of blockages.
The conical a also have a racking arm to enable the beer to be drawn off without and sediment being drawn into the finished beer. Oxygen can also be added without fear of contamination, in fact from the hot side (boil kettle) to cask or bottle the beer never sees the light of day so more or less zero chance of any airborne contamination.

[donchiquon]

Same recipe but different Hop additions.

Same OG, same mash schedule, same yeast, cooled to same final temp (within 0.5c at least) brewed on different days however but similar daytime temperature.

So it boils down to oxygenation possibly, both brews were dropped into the fermenters from a reasonable height, no further mixing was was carried out, both brews had 3 to 4 inches of foam in the fermenters by the time the transfer had finished.

2nd brew is still chugging along, may take a peak and gravity today, see if its dropped below what they 1st brew was totally finished at.

Do both FVs have the same thickness plastic wall?

If the fast ferment had a thicker wall this may insulate more and allow the wort to self-heat to a higher temp during the first few days.

I guess this would speed up fermentation?....