Evaporation

[skinfull]

Can anyone tell me what the evaporation rate would be on a 20 litre batch with a very good rolling boil.

[Jymbo]

Ray Daniels quotes a figure of 5% per hour. Personally I've been using DaaB's batch sparge calculator with a figure of 15% for 1.5 hours and it's always been pretty accurate, so I suppose the figure is probably between 5 and 10% dependent on the vigour of the boil.

[Aleman]

Just to add to this.

The amount of thermal loading that you apply to the beer can affect the outcome. My Bruheat boiler used to hit over 20% evaporation and my beers were darker and 'maltier' the 10Gallon Electric boiler was down at around 12% and beers were lighter in colour. The Gas boilers are around 8% and the beers are much lighter and not as malty . . . although fairly full bodied.

As the heat goes up (and evaporation) the amount of melanoidin production increases, hence the darkening and bigger malt profile . . . . it is possible to simulate a decocted mash using a single infusion mash by boiling the wort hard (> 20% Evaporation), obviously by reducing the amount of heat applied (to below 10%) then you get much cleaner tasting beers.

Another technique to consider once you have 'nailed' basic brewing

[MightyMouth]

That is interesting Aleman, It also makes me happy as I have bought a gas burner and I would prefer cleaner tasting beers to maltier beers and hopefully this will be easier to achieve with the gas system.

[Graham]

Just to add to this.

The amount of thermal loading that you apply to the beer can affect the outcome. My Bruheat boiler used to hit over 20% evaporation and my beers were darker and 'maltier' the 10Gallon Electric boiler was down at around 12% and beers were lighter in colour. The Gas boilers are around 8% and the beers are much lighter and not as malty . . . although fairly full bodied.

As the heat goes up (and evaporation) the amount of melanoidin production increases, hence the darkening and bigger malt profile . . . . it is possible to simulate a decocted mash using a single infusion mash by boiling the wort hard (> 20% Evaporation), obviously by reducing the amount of heat applied (to below 10%) then you get much cleaner tasting beers.

Another technique to consider once you have 'nailed' basic brewing

A major influence on wort darkening is the physical size of the element. The tiny little elements, like jug-type kettle elements, that are in vogue these days darken the wort considerably. It is all that energy concentrated in a small space that produces a fierce hot spot.

When the recipes for the books were tested, our little group met up to compare them from time to time, and the most startling difference between beers from the same recipe, using identical ingredients (I supplied them), was the colour. Widely different. It turned out to be the physical size of the element in the various different boilers employed. A Burco with a hidden element the lightest. A Burco with a large internal element slightly darker. The Electrim type with the old-fashioned kettle element considerably darker still. And the darkest being a small, tiny, modern (for then) kettle element. Strangely, the darkest wort was produced by a 2.4kW element while the others were around 3kW. It is the physical area over which the introduced heat is distributed that has the greatest influence.

I think that when kettle elements have dried up (inevitable in my view) and people are forced to move to Immersion heater elements, there will be positive benefits in this respect. The bigger the better, although probably the 11-inch ones will be the most suitable.

Also, the physical size of the element makes a big difference to the apparent ferocity of the "rolling boil". With a boiler with an integral, hidden element, the boil doesn't look anywhere near as spectacular as one with a small element offset to one side. The hidden element distributes the heat more evenly, whereas the little element sets up fierce convention currents that makes the boil look much bigger, particularly as it is offset to one side.

Again, the bent-over bit on an 11-inch immersion heater should provide a convention current that will enhance the necessary mechanical action of the boil.

[Andy]

Very interesting Graham!

[Jim]

Hmm. I wonder where that leaves my dual fuel system.

[prodigal2]

Hmm. I wonder where that leaves my dual fuel system.

Ahead of the curve Jim And maintaining the fine tradition of brewing, to suite yourself

[Graham]

How light to you want it though Graham ? My 2.4kw element system in a 33L boiler has produced some very pale blonde ales indeed. It may darken it in a 25L boiler.
Were the volumes of the boilers all the same ?

Yes, well, everybody would defend their own pet method.

The volumes of the boilers should not make any difference, in theory at least,; it is the hot-spot that caramelises the wort and that has nothing to do with volume.

I wish that I could guarantee, that if I used my integral element Burco I could produce a far paler beer than you ever could with 2.4kW in a bucket, but I am not prepared to rise to my own challenge. For once this is something that I know I am right about because it is a direct experience. You didn't ask how dark though. The response could have been quite different had you'd asked.

No! No point now. I'm going to bed.

In fact, just a little bit of subjective thought, or a bit of common sense would show that it has substance to it.

Anyway, I'm still going to bed!