# Kettle Shape And Boil Losses Survey - Record Your Figures Here



## PistolPatch (13/7/09)

I'm hoping a few brewers can take the time to record their kettle shape and boil-off statistics in this thread using the template I have supplied at the end of this post.

It might help a few new brewers know where to start and some intermediate ones to be less paranoid about the figures they are getting seeing as percentages get quoted so much. I have been gathering a few figures on the side from some brewers and it is interesting to note the variance when you only talk percentages - 10 to 24% so far. A high evaporation rate in a high surface area kettle does not mean that a brewer is doing a stupidly high boil so please don't be quick to jump in and criticise anyone who does supply their figures.

In home brewing, our kettles vary immenseley. I use a 70lt Robinox pot with a 45cm diameter whereas a common keggle diameter is 33cm or so. In surface area this makes a huge difference. (1590 square cm as to 855) according to this calculator.)

Anyway, hopefully this can be an interesting thing to explore and investigate as there is very little info on this around.

I am happy to record all the figures into a spreadsheet and post the spreadsheet up here on AHB regularly or at least to those who contribute depending on the response.

For now, I think people only need fill out the following template as I think I can calculate all the rest. Straight after this post, I will do a sample reply post. (Hopefully, I will score Post #2 :icon_cheers: )

If you don't want to post your figures publicly, feel free to email them here

Thanks in advance,
PP

START OF TEMPLATE

How would you describe your kettle (keggle/pot/urn/other):
How long was your boil?:
What was your pre-boil volume?:
What was your post-boil volume?:
What is the diameter of _*the body*_ of your kettle?:
What is the diameter of the opening to your kettle? (should be same as above for pot or urn):
What is the depth of your pot/kettle?:
Do you cover your pot/kettle in any way during the boil? If so by how much and when?:
On a scale of 1 to 10 how confident are you in your figures?:

END OF TEMPLATE


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## PistolPatch (13/7/09)

START OF TEMPLATE

How would you describe your kettle (keggle/pot/urn/other): 70lt Robinox Pot
How long was your boil?: 90 min
What was your pre-boil volume?: 33.5 lts
What was your post-boil volume?: 24.1
What is the diameter of _*the body*_ of your kettle?: 45cm
What is the diameter of the opening to your kettle? (should be same as above for pot or urn): 45cm
What is the depth of your pot/kettle?: 45cm
Do you cover your pot/kettle in any way during the boil? If so by how much and when?: No
On a scale of 1 to 10 how confident are you in your figures?: 9

END OF TEMPLATE
[/quote]


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## PistolPatch (13/7/09)

Here's another one I have copied from another brewer although I don't have his urn dimensions.

START OF TEMPLATE

How would you describe your kettle (keggle/pot/urn/other): 40lt Urn
How long was your boil?: 90 min
What was your pre-boil volume?: 31.0 lts
What was your post-boil volume?: 25.0 lts
What is the diameter of _*the body*_ of your kettle?: Not sure 
What is the diameter of the opening to your kettle? (should be same as above for pot or urn): As above
What is the depth of your pot/kettle?: Not sure
Do you cover your pot/kettle in any way during the boil? If so by how much and when?: No
On a scale of 1 to 10 how confident are you in your figures?: 9

END OF TEMPLATE


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## LLoyd (14/7/09)

START OF TEMPLATE

How would you describe your kettle (keggle/pot/urn/other)ot
How long was your boil?:75min
What was your pre-boil volume?:31
What was your post-boil volume?:24
What is the diameter of _*the body*_ of your kettle?:457mm
What is the diameter of the opening to your kettle? (should be same as above for pot or urn):457mm
What is the depth of your pot/kettle?:403mm
Do you cover your pot/kettle in any way during the boil? If so by how much and when?:no
On a scale of 1 to 10 how confident are you in your figures?:9

END OF TEMPLATE
START OF TEMPLATE

How would you describe your kettle (keggle/pot/urn/other)ot
How long was your boil?:75min
What was your pre-boil volume?:31
What was your post-boil volume?:24
What is the diameter of _*the body*_ of your kettle?:457mm
What is the diameter of the opening to your kettle? (should be same as above for pot or urn):457mm
What is the depth of your pot/kettle?:403mm
Do you cover your pot/kettle in any way during the boil? If so by how much and when?:no
On a scale of 1 to 10 how confident are you in your figures?:9

END OF TEMPLATE


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## Thirsty Boy (14/7/09)

I hate to complicate matters - but boil off is a variable not a fixed amount. I am happy to contribute my figures.. but they are what I made them, not just what happens. I can go up or down by quite a margin by tweaking my set-up.

How would you describe your kettle (keggle/pot/urn/other): Keggle
How long was your boil?: 90min
What was your pre-boil volume?:30L
What was your post-boil volume?:23.5L
What is the diameter of the body of your kettle?: keggle diameter
What is the diameter of the opening to your kettle? (should be same as above for pot or urn):10cm less than keggle diameter (ie 5cm rim)
What is the depth of your pot/kettle?: Keggle depth
Do you cover your pot/kettle in any way during the boil? If so by how much and when?: Not usually. As needed.
On a scale of 1 to 10 how confident are you in your figures?: 10

I can say 10 for confidence - because as I said, I make the system perform to that level. My pre and post boil volumes are set and I adjust, tweak, change etc in order to make sure I hit them - as the boil progresses if necessary.


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## Screwtop (14/7/09)

Same as TB above, figures are general, I can vary the boiloff rate but try to judge boil rate to suit prevailing conditions. I boil for varying times but work on a L/hr rate. Lots of variables in the boil affect boiloff rate. Percentage rates only work if your variables remain the same, same wort, same volume, same amount of heat, weather conditions etc. Kettle surface area and opening are fixed. I loose roughly the same amount per hour to boiloff when doing a single batch as for a double batch. 



How would you describe your kettle (keggle/pot/urn/other):SS fabricated pot
How long was your boil?:90min
What was your pre-boil volume?:58
What was your post-boil volume?:46
What is the diameter of the body of your kettle?:400mm
What is the diameter of the opening to your kettle? (should be same as above for pot or urn):400mm
What is the depth of your pot/kettle?:660mm
Do you cover your pot/kettle in any way during the boil? If so by how much and when?:no
On a scale of 1 to 10 how confident are you in your figures?:9


Screwy


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## Barry (14/7/09)

How would you describe your kettle (keggle/pot/urn/other): 30 L plastic old fermenter
How long was your boil?: 90 mins
What was your pre-boil volume?: 30 L
What was your post-boil volume?: 25 L
What is the diameter of the body of your kettle?: 32 cm
What is the diameter of the opening to your kettle? (should be same as above for pot or urn): 32 cm
What is the depth of your pot/kettle?: 39 cm
Do you cover your pot/kettle in any way during the boil? If so by how much and when?: No
On a scale of 1 to 10 how confident are you in your figures?: 9+

Use immersion heaters, and it is filled to the brim.


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## Ronin (14/7/09)

As with others, the evaporation figures vary depending on how many rings on the burner I have going. But with rings 2 and 3 of a 4 ring burner going:

How would you describe your kettle (keggle/pot/urn/other): Pot
How long was your boil?: 90 Min
What was your pre-boil volume?: 37L
What was your post-boil volume?: 27L
What is the diameter of the body of your kettle?: 42cm
What is the diameter of the opening to your kettle? (should be same as above for pot or urn): 42cm
What is the depth of your pot/kettle?: 40cm
Do you cover your pot/kettle in any way during the boil? If so by how much and when?: I cover it until it boils, then the lid is completely off during the 90 minute boil.
On a scale of 1 to 10 how confident are you in your figures?: 9, this is very repeatable and predictable in my setup.

EDIT: I would say my boil is slightly rolling. Used to go with a much more vigorous boil, but I no longer think it's necessary.


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## PistolPatch (14/7/09)

Thanks a heap for jumping in so quickly with your figures :icon_cheers:

I'm wondering if I should have asked in the template for a description of the boil, something like...

*How would you describe your boil? (Simmer, slightly rolling, medium roll, vigorous, jumpy!):*

Maybe if you could add that as well.

Just aiming for your average here so don't be worried about your variance. It'll just be interesting to see how much the shape affects things on average as it is hard to find formulas for this stuff.

Any extra feedback is great also such as Screwtop provided on the difference between single and double batches in the same kettle.

Many thanks again!
Pat


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## TidalPete (14/7/09)

START OF TEMPLATE

How would you describe your kettle (keggle/pot/urn/other): 70lt Robinox Pot
How long was your boil?: 90 min
What was your pre-boil volume?: 38.0 litres
What was your post-boil volume?: 29.0 litres
What is the diameter of _*the body*_ of your kettle?: 450mm
What is the diameter of the opening to your kettle? (should be same as above for pot or urn): 450mm
What is the depth of your pot/kettle?: 450mm
Do you cover your pot/kettle in any way during the boil? If so by how much and when?: No
On a scale of 1 to 10 how confident are you in your figures?: 9
How would you describe your boil? (Simmer, slightly rolling, medium roll, vigorous, jumpy!): vigorous

END OF TEMPLATE


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## barry2 (14/7/09)

How would you describe your kettle (keggle/pot/urn/other): Stainless steel stockpot
How long was your boil?: 75 min on electric stove hotplate
What was your pre-boil volume?: 10L
What was your post-boil volume?: 8.8L
What is the diameter of the body of your kettle?: 28cm
What is the diameter of the opening to your kettle? (should be same as above for pot or urn): 28cm
What is the depth of your pot/kettle?: 20cm
Do you cover your pot/kettle in any way during the boil? If so by how much and when?: Fully covered until near boil and then 80% covered with a heavy glass lid when boiling.
How would you describe your boil? (Simmer, slightly rolling, medium roll, vigorous, jumpy!):Medium roll
On a scale of 1 to 10 how confident are you in your figures?: 9


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## warra48 (14/7/09)

START OF TEMPLATE

How would you describe your kettle (keggle/pot/urn/other): *40 litre aluminium pot*
How long was your boil?: *75 minutes*
What was your pre-boil volume?: *31.25 litres*
What was your post-boil volume?: *26 litres*
What is the diameter of _*the body*_ of your kettle?: *38 cm*
What is the diameter of the opening to your kettle? (should be same as above for pot or urn): *38 cm*
What is the depth of your pot/kettle?: *36 cm*
Do you cover your pot/kettle in any way during the boil? If so by how much and when?: *No cover*
On a scale of 1 to 10 how confident are you in your figures?: *9*

END OF TEMPLATE


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## troopa (14/7/09)

PP i wouldn't go with descriptions as thats really an unknown.. maybe a degrees C would be more of an accurate measure or boil or a range of degrees if the brewer is the type to fiddle

START OF TEMPLATE

How would you describe your kettle (keggle/pot/urn/other): 60L alumium Pot
How long was your boil?: 60mins
What was your pre-boil volume?: 31.2L
What was your post-boil volume?: 26.1L
What is the diameter of the body of your kettle?: 44cm
What is the diameter of the opening to your kettle? (should be same as above for pot or urn): 44cm
What is the depth of your pot/kettle?:40cm
Do you cover your pot/kettle in any way during the boil? If so by how much and when?: no
On a scale of 1 to 10 how confident are you in your figures?: 7.5

END OF TEMPLATE

*** Temp 102-104C

Edit... Dunno if anyone else has run any of the evap figures yet but im seeing a huge trend of evap being over 20-25%
either that or my calcs are WAAAAAAY off

Edit 2 made a whoopsy and added total volume of water at mash in


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## rude (14/7/09)

How would you describe your kettle (keggle/pot/urn/other):keggle
How long was your boil?:90min
What was your pre-boil volume?:34 litres
What was your post-boil volume?:26 litres
What is the diameter of _*the body*_ of your kettle?:keggle dia 400mm
What is the diameter of the opening to your kettle? (should be same as above for pot or urn):300mm
What is the depth of your pot/kettle?:380-400mm
Do you cover your pot/kettle in any way during the boil? If so by how much and when?:no
On a scale of 1 to 10 how confident are you in your figures?:9
boil is medium rolling


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## haysie (14/7/09)

How would you describe your kettle (keggle/pot/urn/other):keggle
How long was your boil?:75min 90min, depends on the bill and the style, more the bill
What was your pre-boil volume?:32
What was your post-boil volume?:25
What is the diameter of the body of your kettle?:keggle
What is the diameter of the opening to your kettle? (should be same as above for pot or urn):keggle less 60mm
What is the depth of your pot/kettle?:keggle
Do you cover your pot/kettle in any way during the boil? If so by how much and when?:yes, until a simmer is reached, then adjust the opening of the keggle to suit the conditions
On a scale of 1 to 10 how confident are you in your figures?:7 always room for improvement, hate to be a knowitall.


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## PistolPatch (14/7/09)

Thanks again for all the figures. I will whack them into spreadsheet form on the weekend if not before.

The more figures, the better.

Please keep recording the vigour of your boil as I will include that in the sheet as well.

:icon_cheers: 
Pat


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## PistolPatch (14/7/09)

Sorry troopa, I missed your questions.

The description is very subjective I know but I think it is the best we can do. If we start doing wort temperatures then we'll have to record height above sea level too etc!!! I think the description will do for our very primitive purpose here.

As for the evaporation figures, to work out the percentage, get the boil off volume (litres at start of boil minus litres at end) per hour and then divide that by the litres at start then multiply by 100. Confused? Here are your figures...

(31.2lts -26.1lts) x 60 / 60 (your boil length) = 5.1lts per hour

5.1/31.2 x 100 = 16.4%

For a 90 minute boil such as Screwtop recorded in Post #6, it goes as follows...

(58lts - 46lts) x 60 / 90 (his boil length) = 8lts per hour

8/58 x 100 = 13.8%

Hope that helps.

Cheers and thanks,
Pat


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## Leigh (14/7/09)

PistolPatch said:


> Sorry troopa, I missed your questions.
> 
> The description is very subjective I know but I think it is the best we can do. If we start doing wort temperatures then we'll have to record height above sea level too etc!!! I think the description will do for our very primitive purpose here.
> 
> ...



Just fixing your units Pat...your percentages are per hour, not total percentage.


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## PistolPatch (14/7/09)

Thanks Leigh. I'm a lazy bugger :lol:


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## Back Yard Brewer (14/7/09)

How would you describe your kettle (keggle/pot/urn/other): 98ltr Robinox
How long was your boil?: 60min
What was your pre-boil volume?: 85ltrs
What was your post-boil volume?: 75ltrs
What is the diameter of the body of your kettle?: 500mm wide (yeah, I know you want the diameter but it is bloody cold out in the shed tonight)
What is the diameter of the opening to your kettle? (should be same as above for pot or urn): As above
What is the depth of your pot/kettle?: 500mm
Do you cover your pot/kettle in any way during the boil? If so by how much and when?: yes. From the start. Normally have the lid resting over a 1/4 of the opening.
On a scale of 1 to 10 how confident are you in your figures?: 9

Just to throw a spanner in it, I made a brew on the week-end. Pre-boil of 85L, post boil of 75L. I threw some flame out hops in waited around 15-20mins and when I measured it again I had 70L  The brewery was sitting in the same place all the time. I put it down to shrinkage and evaporation. If anyone can explain otherwise.


BYB


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## Damian44 (14/7/09)

Heres my figures

How would you describe your kettle (keggle/pot/urn/other): 80lt ally pot
How long was your boil?: 90 min
What was your pre-boil volume?:47 lts
What was your post-boil volume?: 35
What is the diameter of the body of your kettle?: 48cm
What is the diameter of the opening to your kettle? (should be same as above for pot or urn): 48cm
What is the depth of your pot/kettle?: 40cm
Do you cover your pot/kettle in any way during the boil? If so by how much and when?: No
On a scale of 1 to 10 how confident are you in your figures?: 7


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## floppinab (14/7/09)

Interesting thread Pete, something thats on mind a lot given my kettle is likely to be one of the most "flat" around I think. As a result I lose on average around 35% of my pre-boil on a 75 min boil. When I first started AG with this it took me a while to understand why my gravs where 5 points or so higher than I was expecting.

START OF TEMPLATE

How would you describe your kettle (keggle/pot/urn/other): 100L old butchers bin
How long was your boil?: 75 min
What was your pre-boil volume?: 37.0 lts
What was your post-boil volume?: 23.0 lts
What is the diameter of the body of your kettle?: 57cm
What is the diameter of the opening to your kettle? (should be same as above for pot or urn): As above
What is the depth of your pot/kettle?: 38cm
Do you cover your pot/kettle in any way during the boil? If so by how much and when?: No
On a scale of 1 to 10 how confident are you in your figures?: 9

END OF TEMPLATE 

I boil pretty low generally to minimize the high losses I already have.


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## matti (15/7/09)

This was approximately the number I calculated my equipment to.

How would you describe your kettle (keggle/pot/urn/other): 76lt S/S pot
How long was your boil?: 90 min
What was your pre-boil volume?:33
What was your post-boil volume?:25
What is the diameter of the body of your kettle?: 43
What is the diameter of the opening to your kettle? (should be same as above for pot or urn):43
What is the depth of your pot/kettle?: 37
Do you cover your pot/kettle in any way during the boil? If so by how much and when?: No
On a scale of 1 to 10 how confident are you in your figures?: 8

I use a Rambo burner at 3/4 with a vigorous boil.


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## PistolPatch (16/7/09)

Back Yard Brewer said:


> Just to throw a spanner in it, I made a brew on the week-end. Pre-boil of 85L, post boil of 75L. I threw some flame out hops in waited around 15-20mins and when I measured it again I had 70L  The brewery was sitting in the same place all the time. I put it down to shrinkage and evaporation. If anyone can explain otherwise.
> 
> BYB



Probably mainly just one of those measurement inaccuracies we all get from time to time no matter how well we think we measured - I hate that! With your wide pot, if you have the lid off while cooling, it is still going to evaporate a fair whack. Be interesting to see if this continues to happen to a big degree for you.

The expansion of water is exponential so this, as you reckon, could account for a few litres too. If your wort somehow dropped to 80 degrees, you would have lost about 1.2lts.

Just for interest interest and to give me practice uploading a spreadsheet, the following table shows how much 100lts of water expands between 0 and 100 degrees celsius. I've also whacked in the correction factor you need at each temperature. (I used some online calculator so it doesn't start at precisely 100 litres for some reason but you'll get the idea.)

View attachment Water_Expansion_0_to_100_degrees_Celsius.xls


Drinking is often a lot more fun than measuring  

Many thanks to those like BYB who threw their figures in over the last few days.

Pat


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## PistolPatch (18/7/09)

Here's a spreadsheet with your figures to date...

View attachment AHB_Evaporation_Figures_Record.xls


I have sorted them from largest surface area down and you'll see that surface area is the critical factor which is as expected.

Just for fun, I whacked in an "X Factor," with this being the volume loss per hour divided by the surface area. I then tested how well using the average X Factor is to predict volume losses based solely on surface area. You'll see the results in the last 3 columns.

It's probably as good as any other figure given to people when they are starting out and might save them the "twenty questions," game that you have to play when using an evaporation percentage figure. Also as, Screwtop says, you can pretty much expect the same volume loss in the same pot whether you are doing a single or a double batch.

Feel free to throw some more figures here if you want and I'll update the spreadsheet if this happens. (I'll have over another 5 to throw in here from other brewers by the end of next week.)

:super: for throwing in all your figures. I reckon it is always interesting to see them.

Spot,
Pat

P.S. Some figures in the spreadsheet are in brown. These are figures I had to have a guess at.


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## crundle (20/7/09)

How would you describe your kettle (keggle/pot/urn/other): 40 litre Crown Urn
How long was your boil?: 90 min
What was your pre-boil volume?: 33.0 litres
What was your post-boil volume?: 25.0 litres
What is the diameter of the body of your kettle?: 340mm
What is the diameter of the opening to your kettle? (should be same as above for pot or urn): 340mm
What is the depth of your pot/kettle?: 585mm
Do you cover your pot/kettle in any way during the boil? If so by how much and when?: No
On a scale of 1 to 10 how confident are you in your figures?: 9
How would you describe your boil? (Simmer, slightly rolling, medium roll, vigorous, jumpy!): vigorous

Boiled using a 2400W over the side immersion heater instead of the thermostat controlled internal element, and the urn sides are covered with a 10mm camping mat


cheers,

Crundle


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## pants (26/7/09)

START OF TEMPLATE

How would you describe your kettle (keggle/pot/urn/other): 98 litre Robinox pot
How long was your boil?: 1 hour
What was your pre-boil volume?: 66 litres
What was your post-boil volume?: 52 litres
What is the diameter of the body of your kettle?: 500 mm
What is the diameter of the opening to your kettle? (should be same as above for pot or urn): 500 mm
What is the depth of your pot/kettle?: 500 mm
Do you cover your pot/kettle in any way during the boil? If so by how much and when?: No
On a scale of 1 to 10 how confident are you in your figures?: 8

END OF TEMPLATE


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## PistolPatch (2/8/09)

Sorry crundle and pants for taking so long to add your figures in. I'm still trying to clean up my apartment from Australia's Biggest Brew Day .

I have added your figures and those of mine for double-batches. Like Screwtop, my evaporation rate per hour in litres pretty much remains the same which means the percentage drops from 18.7% to 10.8%.

Here's the latest spreadsheet including your figures.

View attachment AHB_Evaporation_Figures_Record.xls


Thanks guys :icon_cheers:


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## pants (4/8/09)

pants said:


> How long was your boil?: 1 hour



You've got me down for a 90 minute boil on the spreadsheet, PP.


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