My evaporation rate is going up. I use a Crown 40 litre concealed element urn. Whereas I used to lose around 5 litres for a 90 minute boil, now I am losing over 6 litres. I haven't changed anything, and I couldn't describe my boils as vigorous. Better than rolling but by no means vigorous. I do scrape the element cover with my stirrer after mashout, but have done that for a long time now. It is throwing out my calculations and I am reduced to squeezing every last drop of wort out of the trub. Does anybody have any idea why this is happening?
Desperate Bob
Post #2 made 13 years ago
How is the climate changing from when you had 5L vs 6L evaporation? Lower humidity generally means higher evaporation. How about wind? Are you brewing outdoors in the wind?
Post #3 made 13 years ago
BrickBrewHaus wrote:How is the climate changing from when you had 5L vs 6L evaporation? Lower humidity generally means higher evaporation. How about wind? Are you brewing outdoors in the wind?
We are moving towards winter, and the humidity is definitely down, but I am looking back over about 18 months worth of figures. One thing that does stand out, for the last few brews I have had to use a pedestal fan because there has been no breeze. I brew outside under my pergola and use the fan to prevent condensation buildup above the urn. I don't aim the fan at the urn but to one side. Do you think that despite the boil being the same as usual, that the extra evaporation could be caused by the passing air stream?
Last edited by BobtheBrewer on 08 May 2012, 20:04, edited 3 times in total.
Post #4 made 13 years ago
A couple of comments come to mind...BobtheBrewer wrote:We are moving towards winter, and the humidity is definitely down, but I am looking back over about 18 months worth of figures. One thing that does stand out, for the last few brews I have had to use a pedestal fan because there has been no breeze. I brew outside under my pergola and use the fan to prevent condensation buildup above the urn. I don't aim the fan at the urn but to one side. Do you think that despite the boil being the same as usual, that the extra evaporation could be caused by the passing air stream?
1)How many brews did you use to come up with a 5L evaporation rate? I ask because you say the last 18 months you've had higher than 5L. Maybe the 5L evaporation rate was achieved under different circumstances or incorrect measurements (if you used only a couple of brew sessions). I would be much more inclined to trust 18 months of figures. Plus, conditions are probably constantly evolving, whether its the performance of your equipment, climate conditions, etc. Your figures need to evolve with them.
2)If its the last couple of brews that are throwing you off, done under less windy conditions, then that's a slightly different story. Most of the time, wind (I think because I brew indoors) reduces evaporation for those using a gas-fired kettle because heat is blown out between the flame and kettle bottom. This can, of course, be countered by increasing the gas flow to achieve the same boil vigor. In your case, though, a heating element shouldn't be prone to wind effects. Wind could decrease evaporation in your case as its slightly cooling the wort by pulling heat out the side of the urn. That might explain why your last few brews, little/no wind, have had higher evaporation rates?
3)How's your OG being affected? I assume its slightly higher than expected? If you notice that evaporation is going to be higher than desired AND the gravity will be higher than desired, you can add in the appropriate amount of water to the boil. Easy solution. That's one of the great things about taking frequent measurements. It gives you time, and usually more options, to correct mistakes or abnormalities.
Last edited by BrickBrewHaus on 08 May 2012, 21:09, edited 3 times in total.
Post #5 made 13 years ago
I brewed in the rain last weekend and ended up boiling for an extra 30 minutes.Is this because of the near 100 percent humidity?
AWOL
Post #6 made 13 years ago
Nah, probably evaporating only slightly faster then you were collectingLylo wrote:I brewed in the rain last weekend and ended up boiling for an extra 30 minutes.Is this because of the near 100 percent humidity?
Could've been a humidity thing. Could also be a situation where the rain is slightly cooling the wort and reducing boil vigor. I'll allow PP to jump in now and talk to you about never believing a single measurement from a single brew day
Last edited by BrickBrewHaus on 09 May 2012, 01:30, edited 3 times in total.
Post #7 made 13 years ago
Yeah I wasn't going to start messing with his beloved formulas without some solid stats.I actally though I was running a harder boil than usual.I will know in a couple of weeks but I suspect that what I will end up with is..BEER!
AWOL
Post #8 made 13 years ago
When I brewed indoors I had a problem with condensation dripping into by brew from above.BrickBrewHaus wrote: I brew outside under my pergola and use the fan to prevent condensation buildup above the urn. I don't aim the fan at the urn but to one side.
I solved the problem by fixing a towel across the cooker hood.
Last edited by Yeasty on 09 May 2012, 04:11, edited 3 times in total.
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Post #9 made 13 years ago
Good Day, One explanation is cold air cannot hold water vapor as much as warm air...Think about Dew point, The fact that air at 5C can have humidity of 95%, and when heated to 25C the humidity is 4%.
The warm temperatures of Summer can cause Dryer air that can hold much more water than cool humid air.
Or maybe it's just an American thing
The warm temperatures of Summer can cause Dryer air that can hold much more water than cool humid air.
Or maybe it's just an American thing
Honest Officer, I swear to Drunk, I am Not God.
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Post #10 made 13 years ago
Hi Bob
Experienced a similar thing with my Crown 40 L concealed element urn. But I can partly explain my differences due to the weather. First 20 brews averaged 3.3 litres per hour evaporation, from March to October then next 20 averaged 3.5 litres per hour since October to now. That said I am getting higher evaporation rates now than at the same time last year.
I brew in an unheated garage and use a fan to direct the air stream away above the urn. Plus it is colder here in Tasmania than sunny Queensland so my evaporation rates are lower.
cheers
Ian
Experienced a similar thing with my Crown 40 L concealed element urn. But I can partly explain my differences due to the weather. First 20 brews averaged 3.3 litres per hour evaporation, from March to October then next 20 averaged 3.5 litres per hour since October to now. That said I am getting higher evaporation rates now than at the same time last year.
I brew in an unheated garage and use a fan to direct the air stream away above the urn. Plus it is colder here in Tasmania than sunny Queensland so my evaporation rates are lower.
cheers
Ian
Post #11 made 13 years ago
Excellent point BBHBrickBrewHaus wrote:... never believe a single measurement from a single brew day
Last edited by PistolPatch on 09 May 2012, 07:30, edited 3 times in total.
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Post #12 made 13 years ago
After doing some research into this and my own experiences lead me to believe there are a few factors which affect evaporation significantly
Relative Humidity
Temperature
Air Movement
and perhaps pressure too
If you have air movement the soggy steam will be evacuated more efficientyly from your kettle which allows the surface to evaporate better.
Relative humidity has a similar effect, allowing the 100% humidity steam to diffuse into the environment better, which is why evaporation is low when its raining
And temperature seems to have an effect too, not sure exactly why, but I did do some research into formulas for calculating evaporation and air speed is a variable.
Point is, your evaporation will vary with the local weather conditions, and at least in Sydney we have had a very interestingcold wet summer and we're moving into what feels to me like a drier winter.
Well, that's basically my theories/understandings
If you underestimate your evaporation you can always add back water in the fermenter.
Relative Humidity
Temperature
Air Movement
and perhaps pressure too
If you have air movement the soggy steam will be evacuated more efficientyly from your kettle which allows the surface to evaporate better.
Relative humidity has a similar effect, allowing the 100% humidity steam to diffuse into the environment better, which is why evaporation is low when its raining
And temperature seems to have an effect too, not sure exactly why, but I did do some research into formulas for calculating evaporation and air speed is a variable.
Point is, your evaporation will vary with the local weather conditions, and at least in Sydney we have had a very interestingcold wet summer and we're moving into what feels to me like a drier winter.
Well, that's basically my theories/understandings
If you underestimate your evaporation you can always add back water in the fermenter.
Fermenting: -
Cubed: -
Stirplate: -
On Tap: NS Summer Ale III (WY1272), Landlord III (WY1469), Fighter's 70/- II (WY1272), Roast Porter (WY1028), Cider, Soda
Next: Munich Helles III
5/7/12
Cubed: -
Stirplate: -
On Tap: NS Summer Ale III (WY1272), Landlord III (WY1469), Fighter's 70/- II (WY1272), Roast Porter (WY1028), Cider, Soda
Next: Munich Helles III
5/7/12
Post #13 made 13 years ago
Good Day,
Stux wrote "If you underestimate your evaporation you can always add back water in the fermenter."
I had that problem, so, when the time gets near, I Measure to hot wort level, and stop the boil at the correct volume.
Yes, the 20 minute flavor addition will never be correct, But I am F.W.H. so that doesn't matter!
Stux wrote "If you underestimate your evaporation you can always add back water in the fermenter."
I had that problem, so, when the time gets near, I Measure to hot wort level, and stop the boil at the correct volume.
Yes, the 20 minute flavor addition will never be correct, But I am F.W.H. so that doesn't matter!
Honest Officer, I swear to Drunk, I am Not God.
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Post #14 made 13 years ago
Thanks for all the feedback fellow BIABers. Much food for thought over a few beers. I measure my volumes with a steel ruler, always at the same point in my urn, so I'm confident that figures are correct. I may just wrap a towel around the beam above my urn next time and do away with the fan (unless there is a breeze). I'll keep an extra sharp eye on my next few brews and see how things go.
On a lighter note, I recently had an evaporation problem with a keg. Made a Little Creatures Pale Ale (clone) which was probably the best beer I have ever made. The keg only lasted 5 days so it must have been evaporation!
On a lighter note, I recently had an evaporation problem with a keg. Made a Little Creatures Pale Ale (clone) which was probably the best beer I have ever made. The keg only lasted 5 days so it must have been evaporation!
Post #15 made 13 years ago
Wow Bob, 5 gallon keg in five days? I hope you had help with that one. 
Fermenting:
Bottle Conditioning
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Post #16 made 13 years ago
No mate, only 18 litres, but I didn't inform the wife. It just tasted so goood!rockbotton wrote:Wow Bob, 5 gallon keg in five days? I hope you had help with that one.
Last edited by BobtheBrewer on 09 May 2012, 18:29, edited 3 times in total.
Post #17 made 13 years ago
Bob,Make sure you post the recipe in the Recipes forum as Lylo has been whingeing there aren't enough recipes there
.As for evaporation, like stux said above, there are several factors and they can all make a big difference. If you brew outside, this can make a big difference. You certainly will never get the same evaporation rate from one brew to the next. A 20% variation is not uncommon and should be fully expected.
I set my default to the highest evap rate I think I will get and then just top up my fermentor. Don't squeeze the bag to death to get the right numbers. The only thing numbers are meant for is to get you in the right ball-park or, after a few brews, tell you if you are doing something seriously wrong.
So, all is good unless you don't post your LCPA recipe. Then Lylo may turn nasty
.PP
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