Question about Coopers Real Ale kit

[ProPyro]

So my first two brews were all grain one gallon kits, one turned out "interestingly" and the other is still aging but I don't have high hopes for it. At the suggestion of my LHBS I picked up a Coopers Real Ale extract kit to try and start my learning curve back up again.

When I bought the kit I thought I was buying a kit for a 18.9 liter carboy, after reading through the instructions I realized this was for a 23 liter batch. I'm pretty fortunate that my grandfather has a lot of odds and ends from wine making that I've got free access to. One such example of this fortune is a 25 liter demijohn, that I just ran some PBW through and have some sanitizer sitting in it right now.

Now that the preamble is out of the way, this is my main question. Is 2 liters enough head space in the demijohn for fermentation, or am I going to end up with yeast and wort all over the demijohn and whatever it's sitting on? My only options with demijohns are the 25 liter, a 52 liter, and maybe a 15 liter. I've got 3 18.9 liter carboys and more than enough growlers.

Or better yet, time for a tangent/segway. Would it be acceptable to fill a growler with wort and then throw the rest in either a carboy or the 25 liter demijohn? This way I've got a gallon on the side that I can play with dry hopping, oak, fruit or some other method. Obviously I'm going to have to divide up the yeast.

3.8 liters to the gallon, 7g of yeast to make 23 liters of beer ... so 1.15 grams of yeast should do one gallon and the remainder would treat the main body of the beer. Which now that I think of it, is too big for a 5 gallon carboy and would have to go in the 25 liter demijohn anyways.

Am I doing this right, or am I over complicating things? I'm not going to start this project for another few days, or even a week or two. So I'm not in a particular rush and I'm still pretty busy reading through some resources I've had suggested to me.

 

[CCericola]

2-liters might be enough. You can actual rig up a blow off tube just in case that'll keep your house clean. You could do it in two different demijohns without issue, but I'd avoid trying to ferment in a growler. They are not meant to hold pressure.

If you're super worried about headspace - put it all in the one container, pitch yeast, etc. Then rack out some into another demijohn until you feel better. But just not in a growler.

 

[unionrdr]

I hope you meant 25L. Just put it in the 25L & rig a blow off tube into a 1/2 gallon container 1/3 full of water with a splash of starsan. That should contain krausen & co2 blow of,which can be heavy during initial fermentation.

 

[Toga]

Put it in the 25L demijohn and add a liter or 2 less water when you mix it. You will end up with less beer however it will be a tad stronger and tastier

 

[gbx]

I would use the recommended amount of water for the kit. I started with coopers kits and recently did up a couple after 50+ all grain batches. One I did with less water to fit it in a carboy and it is too bitter - in a harsh unpleasant way. If you don't have the head space, split the wort in half and use your carboy for the other half (and maybe ferment half with a different yeast as a fun experiment) You can do tweaks to cooper's kits but I wouldn't mess with the amount of water to add.

 

[ProPyro]

Well, I ended up more or less doing it as instructed. Rather than doing 20 liters in the demijohn and 2 liters in the pot to make the wort I did 18/4 so the wort would be thinner and less likely to caramelize and burn.

Would have been great if my pot wasn't too small and the wort didn't boil over when I added the dextrose. Other than that it was pretty awesome. The wort tasted pretty interesting, never tried it on any of my all grain train wrecks I made earlier. I was actually surprised when I measured the gravity and got 1.042 like I was supposed to.

As for head space in the demijohn, the guys at my LHBS said 25 liters is ample room for the head, so I went with it.