How much headspace for fermentation

[yourlastchance89]

I was gifted a 5 gallon barrel for Christmas. I will be fermenting and aging a Lambic in it. I typically do 5 gallon batches in 7 gallon stainless steel. How much headspace should I have in the barrel for fermentation and aging?

 

[cactusgarrett]

I think the majority of barrel users employ the barrel for aging and not primary fermentation. I could be wrong, as I don't have one. Doing the primary ferment in the barrel would simplify things by allowing you to fill the barrel right up to the bung hole and not worry about any blowout that would come along with a krausen. Just one option.

Since a barrel isn't air-tight, I don't think headspace would be too much of a concern. With a smaller barrel (5gal), you're likely to have it aging less time (more surface area imparts more flavor faster), so I don't think exposure to oxygen will be an issue for a shorter amount of time.

 

[RPh_Guy]

I don't have one either but +1 for this:
Use another vessel for primary fermentation and the barrel for aging (topped up to full).

What was in the barrel?

 

[Dcpcooks]

If you want to use the barrel for primary you’ll need to make a little extra to top off the barrel after primary. You don’t want a lot of head space in the barrel. O2 will bring the potential for acetic acid and a primary in the barrel can have a larger blow off than you may anticipate. You should also have a plan for a blow off tube.

 

[yourlastchance89]

If you want to use the barrel for primary you’ll need to make a little extra to top off the barrel after primary. You don’t want a lot of head space in the barrel. O2 will bring the potential for acetic acid and a primary in the barrel can have a larger blow off than you may anticipate. You should also have a plan for a blow off tube.

Top off with what? More wort? Doesn’t that just re-kickstart fermentation

 

[Dcpcooks]

Yes more wort. You’d make a slightly larger batch than your barrel will hold and ferment it on the side in a small fermentor. Then you add it to the barrel as needed.

Personally I’ve done it both ways and I prefer to start in a fermentor. I say that because it can get messy and unpredictable in a barrel with zero head space.

Once primary is over in a barrel you’ll have head space from blow off. There are lots of variables at play in a primary fermentation with wild yeast in a barrel. It’s pretty hard to predict how strong primary fermentation will be. You don’t want a 1/2 to 1 gallon of head space as you begin a year long aging. You’ll lose enough to evaporation by the time your done.

You’ll also have more evaporation if you have head space as the staves in the headspace will shrink a bit faster and allow more o2 in.

It’s a long haul to finish a lambic. You’ll want to stack the odds in your favor when possible.

Where did the barrel come from? What was in it before?

 

[yourlastchance89]

20 L white oak never used before

 

[howamidriving]

Others with more barrel experience feel free to correct me but...in a 5 gallon first use oak barrel I'd be hesitant to age a lambic in it long term. I suspect you're going to get way to much oak character.

If you have other sours aging right now maybe rack one over to the barrel for a week or two. Or maybe even do a stout or something in it first.

 

[yourlastchance89]

I’ve been getting that consensus. I’ve got a few beers going now I may rack over to it when they’re finished for a few days. I started a new thread on here to get some ideas.