Technique

I’ve been worrying slightly about my efficiency lately.  My last brew was calculated based on a 70% efficiency, aiming at 15 litres at 1.072, but I ended up with 15.5 litres going into the FV at 1.064.  Clearly this is a lot lower than my target.

An evening of Googling and reading later, I’ve realised I’m thinking about this all wrong.

I collected 23 litres of sweet wort from the mash tun at 1.050, and Beer Engine tells me this is 73% efficiency.  It’s this that I should be concerned with, and I did ok.  It was a strong beer (which apparently lowers efficiency), and I still managed 73%.  This is a good thing!

The brew had a 90 minute boil, which lowered the volume to 18 litres and the SG to 1.064.  Again, plugging the numbers into Beer Engine, this has maintained the 73% efficiency, as I’d expect (since all that’s happened is that water has been evaporated away, reducing the volume and increasing the gravity).  Again, this is a good thing, and bang on (in fact slightly above) my target.

What I’ve been getting confused over is the volume into the FV.  This has nothing to do with my efficiency calculations (or, if it does, it’s not a measure of efficiency that anyone cares about).  The drop from 18 litres in the boiler to 15.5 in the FV is simply a loss of wort to absorption into the hops and to the dead-space in the boiler.

If I’m wanting to get 15 litres into the FV, then I need to formulate a recipe based on how much wort I’ll loose to hops and dead-space.  In this case it was 3 litres, so I need to formulate the recipe for 18 litres at 1.072 rather than 15 litres at 1.072.  Certainly it will be a guess based on the amount of hops I’m using in a recipe, but it will be a lot closer to what I’m actually wanting.

Points to keep in mind for future recipes:

1) Formulate the recipe for the volume in the FV + losses to hops (i.e. the total I want at the end of the boil)

2) Calculate the batch sparge volumes for the quantity into the FV (i.e. after the losses to hops)

So: my efficiency is fine. And now I know why, if I have the volume in the FV that I wanted that my gravity is always a few points down.  I can’t believe it’s taken me this long to realise…

When I brew in the kitchen we end up with a steam-room.  Not surprising, really, as I’ve got a big pot of wort boiling away for 90 minutes.  It’s far from ideal, however, since we end up with a ceiling that starts dripping.  So, after some pointed comments from my dear wife, I’ve decided to try venting the steam in a more managed way.

I got some tumble drier venting and a 100mm connector piece, and cut a suitable hole in the boiler lid.

The vent pipe is dropped out of the window, the pipe is supported in the middle so it’s all running uphill, with the idea being that steam will condense when it goes outside and drop out of the bottom of the pipe.

This has turned out to be a qualified success.  Successful in that the amount of steam in the kitchen is significantly reduced, so that’s good.  Qualified in that I can’t just leave the lid fully on, or even only slightly cracked open, I need to keep a good inch or so open at one side, or the damn thing boils over.  So far it’s happened 3 times (as I write I’ve just added the late hops, the cooler coil, and the irish moss), with the inevitably messy results.  I’ve also lost a bunch of the hops in the process, so I threw a few extras in at around half-time.

The problem with the boil-over is probably one of pressure – the vent isn’t getting rid of steam quick enough, and since the liquid level in my boiler is very close to the top any time it gets frothy it ends up boiling over.

Conclusion: worth doing again for the reduction in steam, but I need to be very careful with regard to boil-overs.

Wonder if I can use a fan to vent it a bit quicker?

I thought it worth writing a run down on the equipment used for an extract brew.

You don’t need all this, but it does make life easier; you can manage with a big stock-pot on the stove and cooling in the sink (or even just left over night), but it’s easier to boil the whole 25 litres in a dedicated boiler, and use a chiller to cool it all.

This recipe is for the Exmoor Gold described in my last post.  It’s a very simple recipe that just requires dried malt extract (DME) and hops. (more…)

When I started doing extract brews (after a whole 2 kits!), I decided that I’d rather pour small amounts down the sink than a whole 23 litre barrel, so I stuck to 5 litre brew lengths.

This made it a lot easier – I had a 10 litre stock pot I could use for the boil, which was a perfect size for 7 or 8 litres of boiling wort (reduced to around 5 litres after 90 minutes boiling). The pot also fitted the sink quite nicely, which meant I could just cool it in the sink with ice blocks.

The fermentation I did in typical 5 litre water bottles from the supermarket, the lids of which I drilled a 14mm hole in, and fitted a grommet and airlock.

The other thing was keeping a good temperature. The solution to this was a plastic crate, filled with water, in which I stuck an aquarium heater. This maintained a steady 21C for the duration of fermentation.

Now, the brews I did in 5 litre batches didn’t turn out that well – that’s the subject of a future post! – but by the last one I did, Camerons Strong Arm, I seem to have figured a lot of them out, so the only problems I’ve had since then has been silly things like badly sealed caps, and not being able to bottle before going on holiday for the hottest week of the year.

It requires very little equipment, and allows easy experimentation in small quantities.  I thoroughly recommend it.

I should point out, however, that the fermentation can be a little… lively?