Head Space in Fermenters

[AleFred]

i want to do some small all grain batches, just wanted to know whats the optimal head space for wort to ferment in.. my guess was about a gallon and a half considering most of us do 5 - 5.5g batches. i have a 5g carboy that i'd like to use, would a 3.5g or maybe even a 4g batch be suitable for a healthy fermentation?

 

[CidahMastah]

it varies based on your SG reading. So if you have a high SG - you might need more headspace to avoid high krausen blowing through your airlock.

1.5gallons of head space should be good for most of your brews.

That said, you can always put on a blow off and do 4 gallons and hope you only lose a little

 

[AnOldUR]

I ferment 4 gallons in 5 gallon carboys regularly. It's about 50/50 chance of needing a blow-off tube (like said, depends on yeast and gravity.) I normally go the blow off tube route just to be safe.

 

[manoaction]

There is also a product called FermCap that you can get at your LHBS. A drop or two of it will melt away the krausen to keep it from blowing over the top.

Plently here (including me) us it and like it.

 

[Thehopguy]

Im wondering why u wouldn't just do a 5 gallon batch, its about the same amount of work..and you'll wish you had more if it ends up being really tasty

 

[Mpavlik22]

it varies based on your SG reading. So if you have a high SG - you might need more headspace to avoid high krausen blowing through your airlock.

1.5gallons of head space should be good for most of your brews.

That said, you can always put on a blow off and do 4 gallons and hope you only lose a little

I would have to disagree. How exactly does your SG relate to the headspace required? Ideally you want hardly any head space to reduce the possibility of oxidation. The caveat is factoring in the space for the krausen. I would say it depends on the type of yeast used, but even then a blow off tube could b used.

For example, a 1.060 beer using wlp001 will have a large krausen, but a 1.060 beer using wlp029 will not and require less headspace if basing it on yeast krausen.

However I do agree with you on:
1.5gallons of head space should be good for most of your brews.

 

[AleFred]

Im wondering why u wouldn't just do a 5 gallon batch, its about the same amount of work..and you'll wish you had more if it ends up being really tasty

i just simply cant do a full 5 gallon boil just yet(waiting for a few things mash tun and new kettle)..3 is sort of the max i dont know why i said 4

 

[LandoLincoln]

If memory serves correctly, I think using a blow off tube and having krausen exit the fermentor is beneficial to the beer, since the krausen contains potential unwanted materials. But I might be remembering wrong.

 

[CidahMastah]

I would have to disagree. How exactly does your SG relate to the headspace required? Ideally you want hardly any head space to reduce the possibility of oxidation. The caveat is factoring in the space for the krausen. I would say it depends on the type of yeast used, but even then a blow off tube could b used.

For example, a 1.060 beer using wlp001 will have a large krausen, but a 1.060 beer using wlp029 will not and require less headspace if basing it on yeast krausen.

However I do agree with you on:
1.5gallons of head space should be good for most of your brews.

So are you saying a 1.030 gravity brew with WLP001 with have the same Krausen as a 1.070 gravity brew with WLP 001? Didn't think so...

Your SG and yeast directly relates to how much krausen you generate, i.e. how much chance of a blow off you have. Low gravity brews generally have less explosive krausen where high gravity brews tend to have much more. Ferment temp plays in too (higher temp more activity generally).

Once you start fermentation, head space in your fermenter is really a moot point. I do 11g batches in demi johns all the time and never have oxidation issues. CO2 creates a protective blanket over your brew in the primary. I leave in primary for 3 weeks and never have oxidation issues. There is about 4 gallons worth of head space.

 

[AleFred]

i always though krausen had loads of healthy yeast cells and hop particles that would potentially alter the beers taste if "blown off"

 

[AleFred]

I leave in primary for 3 weeks and never have oxidation issues. There is about 3 gallons worth of headspace.

very interesting, that makes me fell a bit better

 

[CidahMastah]

If memory serves correctly, I think using a blow off tube and having krausen exit the fermentor is beneficial to the beer, since the krausen contains potential unwanted materials. But I might be remembering wrong.

I never get blow off from my demi john ferments. Krausen isn't harmfule to beer. It just falls to the bottom and you rack off the beer.

Alefred - do some searches and you will see that many many many brewers are 3 week on the trub fans. In my anecdotal experience, and many others, it produces better beer, and gives the yeast time to clean up by products from the ferment.

 

[Mpavlik22]

So are you saying a 1.030 gravity brew with WLP001 with have the same Krausen as a 1.070 gravity brew with WLP 001? Didn't think so...

No i didn't say that at all. i said it depends on the yeast used. "For example, a 1.060 beer using wlp001 will have a large krausen, but a 1.060 beer using wlp029 will not and require less headspace if basing it on yeast krausen. "

Your SG and yeast directly relates to how much krausen you generate, i.e. how much chance of a blow off you have. Low gravity brews generally have less explosive krausen where high gravity brews tend to have much more. Ferment temp plays in too (higher temp more activity generally).

i disagree again. Ive had some very low gravity beers with explosive fermentations. If you use a packet of liquid yeast and a packet of dry yeast on the same wort, i bet the dry yeast will have alot more explosive fermentation and more krausen. This is because there are more yeast cells in a packet of dry yeast than a packet of liquid.

So it depends on the yeast used, yes the gravity may play a very small role, but its primarily the type and how much yeast you used that is the driving force of the krausen.

 

[Mpavlik22]

If memory serves correctly, I think using a blow off tube and having krausen exit the fermentor is beneficial to the beer, since the krausen contains potential unwanted materials. But I might be remembering wrong.

While the krausen does contain some unwanted materials, it does contain the healthiest yeast in your fermenter. It also contains many proteins responsible for head retention in your beer.

 

[CidahMastah]

No i didn't say that at all. i said it depends on the yeast used. "For example, a 1.060 beer using wlp001 will have a large krausen, but a 1.060 beer using wlp029 will not and require less headspace if basing it on yeast krausen. "



i disagree again. Ive had some very low gravity beers with explosive fermentations. If you use a packet of liquid yeast and a packet of dry yeast on the same wort, i bet the dry yeast will have alot more explosive fermentation and more krausen. This is because there are more yeast cells in a packet of dry yeast than a packet of liquid.

So it depends on the yeast used, yes the gravity may play a very small role, but its primarily the type and how much yeast you used that is the driving force of the krausen.

and my point remains... gravity is a factor.

If the yeast is constant and the gravity increases... so does the krasuen. thus, all things being equal, increased gravity = increased krausen.

Are you denying this causal relationship?


dry vs. liquid isn't the casual factor in your second example, the TYPE of yeast is. You can't compare apples to oranges and draw accurate conclusions. You need to have a control, so you are actually comparing 1 thing, and measuring 1 thing.

 

[Mpavlik22]

and my point remains... gravity is a factor.

If the yeast is constant and the gravity increases... so does the krasuen. thus, all things being equal, increased gravity = increased krausen.

Are you denying this causal relationship?


dry vs. liquid isn't the casual factor in your second example, the TYPE of yeast is. You can't compare apples to oranges and draw accurate conclusions. You need to have a control, so you are actually comparing 1 thing, and measuring 1 thing.

yes as i already stated, gravity plays a very small role. Yeast is the primary factor in krausen tho.

If you have the same wort (1.060) and split it in two batches and pitch 1 vial of wlp001 in one fermenter and 3 vials of wlp001 in the other which will have more krausen? The yeast dictates the krausen volume. No matter if its dry, liquid, or a different type of yeast.

You are correct that in most cases a lower gravity beer will have a smaller krausen, but that is not always the case. I have had some very explosive fermentations making lower gravity session beers, where as i have made barleywine and didn't even need a blow off tube. So "increased gravity = increased krausen" is not true.

 

[CidahMastah]

yes as i already stated, gravity plays a very small role. Yeast is the primary factor in krausen tho.

If you have the same wort (1.060) and split it in two batches and pitch 1 vial of wlp001 in one fermenter and 3 vials of wlp001 in the other which will have more krausen? The yeast dictates the krausen volume. No matter if its dry, liquid, or a different type of yeast.

You are correct that in most cases a lower gravity beer will have a smaller krausen, but that is not always the case. I have had some very explosive fermentations making lower gravity session beers, where as i have made barleywine and didn't even need a blow off tube. So "increased gravity = increased krausen" is not true.

actually on post 6 you said otherwise. Your barley wine was probably drastically under pitched and that is why it didn't have that much krausen.

I would say all things equal in nearly every case that is true. You are just trying to stir the pot dude.

OP question was, how much head space. I answered generally, which was what he was looking for. Generally, gravity will play a roll.

 

[Mpavlik22]

actually on post 6 you said otherwise. Your barley wine was probably drastically under pitched and that is why it didn't have that much krausen.

I would say all things equal in nearly every case that is true. You are just trying to stir the pot dude.

OP question was, how much head space. I answered generally, which was what he was looking for. Generally, gravity will play a roll.

I'm not trying to fight. I just said I disagreed with your post. Where you have some valid points I think I do as well.

I can assure you the barleywine was not under-pitched. As I tried to explain before, different types of yeast produce different amounts of krausen regardless of gravity. BUT as you've pointed out, gravity may affect the krausen also.

I disagreed with your original post b/c you said headspace varies based on SG. Where you have valid points, in my opinion yeast is the main factor of krausen and headspace required with SG coming in third.