Dealing With Kettle Evaporation

[Ecosse]

Hi all,

Using much knowledge gleaned from many hours here (and with parts from Ross & Beerbelly) I've finally cracked my AG cherry

Over the past three weekends I've brewed a Southern English Brown, a Dunkelweizen (both from JZs 'Brewing Classic Styles') and a brown ale (from How to Brew). The smell from all three was terrific and I'm counting the minutes till the first proper tasting.

The process hasn't been as daunting as I'd expected. I've been happy with my efficiencies (go the Millmaster) and have been hitting my gravities OK. Apart from losing a little too much heat in the esky-tun it's been a blast.

My one real issue is the amount of water I'm evaporating off during the boil. My kettle is quite big (60L with a 44cm diameter) and I'm using the Italian spiral burner. It's a powerful little bugger. Even on the lowest heat that maintains a rolling boil I'm losing almost 40% of liquid during the 60 minutes. :blink:

I'm wondering how anyone else who has this problem deals with it. At the moment I'm topping up the fermenter to correct level with filtered water but I'd probably rather add this to the kettle so that it's boiled as well.

Just interested in everyone's ideas.

 

[mika]

Umm, stop boiling so vigourously ?

 

[Tony]

get a smaller burner mate. nothing else for it.

I have a 23 jet Rambo mongolian and its too big for 60 liter boils. I have to turn it down to nothing....... till it soots on an orange flame and it still rolls and gives me 10 liters/hr evaporation.

If your evaproating that much, your probably caramelizing the wort as well. Great in the brown ale but no good in a german pilsner.

Just got my little 10 jet mongolian running on the weekend and will be giving it a run on sunday. It certanly pours out the heat and its only a baby compared to the big rambo.

Not sure of the heat rating of the spiral burners but i recon its lots.

 

[Ecosse]

Umm, stop boiling so vigourously ?

Well I tried that The second two brews were just boiling but the evaporation was still very high.

 

[Stuster]

Do you have a lid that you can cover half the opening with? Or you could try topping up with water as you go. Tony has a good point though.

 

[lobo]

when your wort evaporates, dont you lose your sugars etc? wont topping it up dilute it? or are you only losing water? im interested as i have a nasa burner, and am setting up my brewery saturday for sunday to be AG#1.

Lobo

 

[Stuster]

Lobo, you don't lose the sugars, just the water.

 

[oldbugman]

Sure it's not leaping out of the pot while your not watching? 40% is pretty big.

 

[Adamt]

What size are your boils? Quoting a percentage evaporation rate is redundant unless everyone has the same setup, a better way to quote evaporation is litres per hour.

Turning down the burner while maintaining a good, blue flame is a good idea to reduce output. Or if you're not worried about your gas consumption you can raise your kettle higher above the burner

 

[Tony]

The kettle has a very open top at 44cm......... perhaps make a ring that sits over the top and drop that hole dia back to say 30cm.

this will let the volatiles out but limit some of your evaporation rate.

If you can throttle it right back....... it must be the big opening on the top. 40% or a 20 liter boil is only about 8 liters which would be normal......... as above....... liters/ hr is a better figur to work off. where as 40% of a 50 liter boil would be 20 odd liters which would be very high.

and would be good to know the boil/batch size? a %age figure is relative to batch size and without that we are just guessing

cheers

 

[lobo]

thanks stuster

 

[Kai]

The kettle has a very open top at 44cm......... perhaps make a ring that sits over the top and drop that hole dia back to say 30cm.

Or just prop the slightly ajar on the kettle. I used to do this when I had a large kettle and high evap rate.

Also, before anyone brings it up, I don't think DMS is an issue like this, not when compensating for the excessive evaporation rate.

 

[Ecosse]

Thanks everyone.

My batch size is 19L, I'm starting with about 27L in the kettle and getting about 16L into the fermenter (and then topping up to 19L) so that, according to my rickety maths, is a loss of 55% o) or about 11L/H. This is all with the boil just boiling.

I have a lid I could whack on top and crack it open a bit but I've had the fear of DMS instilled in me. Maybe I should give it a go.

 

[TidalPete]

G'day Ecosse,

A 40% loss is huge. Never heard of a loss like that before.
I know nothing about the heat rating of spiral burners either but think that Tony is correct in recommending that you get a smaller burner.
I have a 70 litre ss pot with a 450mm opening & using a NASA burner loose 13.5% (Or 5 litres) an hour with the lid off & a good rolling boil going.
Raising the kettle may help a little but you will still be wasting all that gas by raising it high enough to get a significant reduction in evaporation.
How high above your burner does the kettle sit?
Using the stand that comes with the NASA my kettle sits 60mm above the burner.

TP :beer:

Just saw your latest post. You may want to think about getting some brewing software to help you with your calcs.

This is all with the boil just boiling.

Something seems to be wrong here mate?

 

[Screwtop]

40% sounds a bit off over 60min. Still, just plug in the value to your brewing software and you will have enough pre-boil volume to end up with your target fermenter volume. Might want a bigger mash tun though, you'll have a high total water volume. Might have to ensure mash PH using 5.2 or something to prevent tannin extraction.

Screwy

40% P/H :blink:

 

[Kai]

I have a lid I could whack on top and crack it open a bit but I've had the fear of DMS instilled in me. Maybe I should give it a go.

If you're evaporating 40% then you're going above and beyond what you need to to avoid DMS. I think you can afford to cut it back a little.

 

[jonw]

If you're evaporating 40% then you're going above and beyond what you need to to avoid DMS. I think you can afford to cut it back a little.

How does leaving the lid on result in DMS? I have a 50L keg-shaped pot, and use one of Beerbelly's Italian burners with the adjustable medium pressure reg. With a ~40L boil, I can easily turn it down enough to maintain a vigourous rolling boil, and lose about 6L over 90min with the lid loosely covering the pot.

Now you've got me worrying about DMS!

Jon

 

[Kai]

If the lid is partially on and your boil is not adequate, then DMS may condense on the underside of the lid and fall back in. With a vigorous boil though I imagine enough would escape through whatever gap you have between lid and pot. Again, I used to always brew like this when I was using my old gear without any issue. I wouldn't worry about it till you can taste it.

 

[Darren]

Kai,

I wonder about your logic.

If only 1% escapes as steam, then 99% falls back in.

Ecosse would be better of boiling for the first 20 or so minutes with the lid off (allow the DMS to escape). Then partially covering the remaining boil.

Personally, I would get a bigger mash-tun and boiler and do bigger batches or as Tony said, turn the gas down a tad.

cheers

Darren

 

[Guest Lurker]

I am yet to be convinced that high evaporation is bad, although there are opinions to the contrary, or that wort can be caramelized with 16 l left in the kettle. I can maybe believe that Maillard reactions are slightly increased in the boil. Assuming you are batch sparging, I would sparge some more, and add water during or after the boil, and enjoy the good hop utilization, and clear beers that result.