Smaller batches

[Shadime]

Hi all,

After being a K&K brewer, I've just started getting into extract brewing and have made a couple of extract brews.
It takes me quite a while to get through the 19l kegs and I'm really keen to keep experimenting.

Would it be an option to brew a smaller amount and only half fill the 19l kegs, or is it better to have 9.5l kegs?

Cheers
Shadime

 

[2cranky]

sure
you will just use more CO2 to fill the space.
otherwise just give a some away. your friends will appreciate it and you will get great feedback!

 

[Shadime]

Cheers, thanks for the reply

Yeah I do give some away but most of my friends brew there own

 

[Merlyn]

Hi Shadime

I had the same dilemma as you a while back. I now brew small 10 litre batches because I want to be able to brew as often as I can and I live in a small apartment so I struggle with space.

I've got 3 9.5 litre kegs and they work a treat. As 2cranky said, you'll use a lot less CO2 than if you half fill a full size corny. The other benefits are that they take up less space (obviously) and are really easy to transport if you want to take a keg to a mate's or the beach.

I've also got two 15 litre fermenters which are nice for 10 litre batches and I can just about squeeze both (one on top of the other) in my under-counter fermenting fridge.

Merlyn

 

[Shadime]

Thanks for the reply

Bought a 15L fermenter today.
Would like to buy some 9.5L kegs but in my enthusiasm to get into kegging Ive got 5 19L kegs.

 

[pcqypcqy]

I was in the same boat as you about 18 months ago, while I experimented a bit and had the time to brew regularly.

9.5l kegs are very exy, and gas and 19l kegs are cheap. I wouldn't bother with them.

No issues half filling a keg. I doubt you'll notice the difference in the cost of gas usage, given a 2.6kg bottle fill is $20 or $25 and lasts many kegs.

 

[Bribie G]

Compared to rocking up to a drive through bottlo and paying $50 for a carton of MegaPiss, gas is, lets face it, cheap as chips.

If partly filling a standard cornie keg with an 11 litre brew out of a 15L fermenter (I have one of those actually that I use for doing a single case of PETs for case swaps or competition brews) it's advisable to do the following:

Fill your keg with water, right up to the lid opening - treated with a dash of starsan or phos.
Connect up to your kegerator and serve the whole keg through a tap, discarding the water via jugs.

You now have a keg full of pure CO2.

When transferring the brew into the keg loosen the lid a crack, then transfer beer into the keg through the beer out post so it wells up from the bottom of the cornie, pushing the CO2 out as it goes. Then seal up tight as a fish's. You'll need to buy a spare beer out QD if you don't already have one.

That way you have a fairly pure CO2 headspace. Half filling a keg just by gravity with the keg half full of air will probably cause oxidisation problems. As you don't drink a lot then you will almost certainly get oxidisation.

 

[Grott]

Other alternative is to buy one 9.5 keg and transfer out or your 19l keg thus getting 2 x 9.5l when required.

 

[Shadime]

Thanks Bribie G,

Couldn't I just purge the headspace a few times?

Cheers

Shadime

 

[Bribie G]

With a half keg headspace you'd be at it for a long time, and probably not get the oxygen out anyway after wasting a heap of gas. A bit like shoving shyte uphill !!!

 

[akx]

My understanding was CO2 was heavier than O2. If you purge with CO2 first and slowly fill from the bottom, I would think you should be ok with 10l on a 19l keg.

 

[Lyrebird_Cycles]

Commonly held supposition but not borne out in practice. The diameter of standard gas lines is such that the exit velocity will inevitably cause turbulence and thus mixing on the exit.

 

[akx]

Thanks for the tip. We always would just crack the CO2 bottle open slightly, and give it a few minutes. Maybe more superstition than functional.

 

[pcqypcqy]

Because I am engineer and I am bored, I made a spreadsheet. I would welcome any/all comments on this as it's been 15 years since I have done any sort of chemistry properly.

Unfortunately I can't attach the spreadsheet - pm me if you'd like a copy.

No matter what the headspace is, the percentage of oxygen you end up with in your headspace remains unchanged (for a given gauge pressure you use to purge). What does change, as has been pointed out, is the amount of CO2 required to achieve this.

Say you did a purge at your serving pressure (10psi say), and you did 3 purge cycles. You'd end up with ~5% oxygen content in your headspace (c.f. 21% in the atmosphere). If you half fill your keg, you will have used 38.6g of CO2 gas to achieve this. If you're totally filling your kegs (say 18 litres), then you only need 3.7g of CO2 to achieve the same result.

So 10 times the purging gas usage if only half filling kegs.

But, gas is cheap. About 1 cent per gram at my shop, so we're only talking a 35 cent difference per keg fill (assuming carbonation usage is the same, which it should be?).

 

[Grott]

Spreadsheet came out ok.

 

[pcqypcqy]

Spreadsheet came out ok.

I just took a screen shot of it to give you an idea of where the numbers came from. Anyone who wants to play with it or check it will probably want to fiddle a bit.

I used to be able to attach spreadsheets but after the migration seems not.

 

[pcqypcqy]

spreadsheet now attached (hopefully)