Process for Charmat Method Sparkling in a Keg

[JustinTG]

Hi all, I’m wondering if there is a “definitive guide” to doing a Charmat method sparkling wine in a keg. We’ve been bottle carbing (no disgorging though) but want to try the Charmat method. At the highest level, I think some of the steps are:

I. Make a clear base wine and transfer to keg.
II. Add sugar yeast mixture
III. Seal
IV. Wait ~ 7 weeks
V. Bottle

Sounds simple but I have a ton of questions. For example:

1) What are the pros and cons of doing this in a commercial keg versus a corny keg (I just learned there was a difference)? The corny kegs are easier but are they less suitable for the pressure?

2) How high can I fill the keg? Can I top it off like I do when doing sparkling in the traditional method?

3) What is the best way to seal the keg? Do you need a pressure gauge or can you just seal the thing up?

4) How much pressure will these kegs withstand? Are there standard ratings? What about things like gaskets?

5) I see that brewers bottle from a keg with a “counter-pressure” filler. Would that work here? Is it as simple as hooking up a hose to the keg and the counter-pressure filler to the host to bottle?

6) Do I still need to use champagne bottles? My physics-delinquent brain tells me that pressure won’t build in the bottle because the fermentation is done. But maybe that’s wrong?

7) Any strategies for dealing with the sediment? Since kegs are tapped from the top, will the sediment stay at the bottom?



These questions are just to add some specificity but I am looking for any general insights and experiences. Thanks all.

 

[BarrelMonkey]

I've only ever done bottle carbonation (traditional/champagne method) but to address some of your points:

1) What are the pros and cons of doing this in a commercial keg versus a corny keg (I just learned there was a difference)? The corny kegs are easier but are they less suitable for the pressure?

2) How high can I fill the keg? Can I top it off like I do when doing sparkling in the traditional method?

3) What is the best way to seal the keg? Do you need a pressure gauge or can you just seal the thing up?

4) How much pressure will these kegs withstand? Are there standard ratings? What about things like gaskets?

A quick Google search suggests that kegs are typically rated to 60psi. This is fine for most beers but not sufficient for sparkling wine. Champagne can get to over 6 atm, which is ~90psi.

Bottom line: Do NOT do this in a keg unless it's a real pressure vessel specifically designed to withstand high pressure. Even if your fermentation goes off successfully, you have to somehow get the (highly pressurized) wine out of the keg and into bottle. How are you going to get the cap off? I've opened several pressurized kegs in my time (not from making sparkling wine, but accidentally pressurized eg if a supposedly finished wine starts to referment). It's very dangerous. (If you have to do this you need to press down hard on the cap with one hand and carefully remove the clamp. Gently release pressure with your hand and let the gas escape as slowly as possible. Beware that the cap may get stuck onto the keg via the gasket, in which case do not leave it like this unattended. The cap can fly off with great force and cause serious injury).

6) Do I still need to use champagne bottles? My physics-delinquent brain tells me that pressure won’t build in the bottle because the fermentation is done. But maybe that’s wrong?

Yes, you absolutely still need to use champagne bottles. The pressure comes from dissolved CO2 which will still be largely there when you bottle the wine. You may lose ~5% of the pressure in a champagne bottle at disgorging, but most of it is still there when you put the final cork/cap in place. Again, these sorts of pressures are no joke. We always wear long sleeves, eye protection and cut resistant gloves when handling non-disgorged sparkling bottles and working on the disgorging line since accidents can happen even under well controlled conditions.

7) Any strategies for dealing with the sediment? Since kegs are tapped from the top, will the sediment stay at the bottom?

Charmat process wines are typically filtered; I assume this needs to be done in some sort of pressure-rated system but I've never done it.