How much do you loose during boil when it's cold outside?

[bnutting]

I have done several AG batches and have never really had much of an issue with this . So either I had a MAJOR brain cramp or I lost more during the boil than I had expected.

I ended up with around 4 Gal after my 60 minute boil. The temp was around 20° F. I swore I had around 6-6.5 Gallons wort collected from my MLT.

I use a turkey fryer for the boil and I KNOW that I only boiled for 60 minutes because I'm anal about it and time everything with my watch. I timed from the start of the hot break.

I guess it's possible that it took a little longer to get to boil due to the colder temps which caused more loss???

But 2 Gallons??? What the heck??

Could I for future winter batches collect a gallon or two in a separate pot and put that on the stove to add after the hot break?? I thought I had seen something like that from one of Yooperchick's posts.

Would I need to make some hops adjustments due to the additions?

Thanks in advance!

 

[the_bird]

More than the cold, I suspect the issue is that the air is a lot drier this time of year. I'd just sparge some more (I've been collecting more like 7.5 - 8.0 gallons to get about 6.0 in the fermenter). Yooper was doing the separate collection, I believe, because she was boiling inside and had to split the boil.

 

[Soulive]

Next time you brew, measure your preboil volume accurately. Also, how much hops did you use? You have to account for some of the wort being lost to trub/hops. Lately it seems to me that I've been losing about 1.5-2 gallons depending on how much hop absorption I have. My last brew I started with 7 gallons (measure accurately) and ended up with 5 gallons in the fermenter...

 

[drunkatuw]

I've been doing some google searching and it appears that evaporation really doesn't depend too much on temperature, but more on relative humidity. But when it's below freezing, the relative humidity drops quickly. Evaporation rate is also determined by the surface area and wind. So if you have a wide boil kettle that is not very deep, you'll have more evaporation than a tall skinny boil kettle. And if the wind is gusting pretty heavy, you'll also lose more volume.

In my searching, I never did find a good formula for calculating the evaporation rate. Best bet is to do as Soulive suggested and measure accurately and then figure out how much you lost and plug it into beersmith (or other brewing program) and you'll know in the future how much you need.

 

[bnutting]

More than the cold, I suspect the issue is that the air is a lot drier this time of year. I'd just sparge some more (I've been collecting more like 7.5 - 8.0 gallons to get about 6.0 in the fermenter). Yooper was doing the separate collection, I believe, because she was boiling inside and had to split the boil.

You know I 'would' boil the 7.5 - 8.0 gallons, however I only have a 7.5 gallon pot and I suspect that I would not have enough head space ;-) Hence the collection into another pot.

Well at least know that I'm not a complete idiot. So do you think that the Yooperchick approach would work?

This was Yooperchick's DFH 60min IPA recipe so there was constant hop additions. But I suspect the large amount of loss was due mostly to the cold/dry air, however I'm sure that the large amount of hops sure added to the loss too.

 

[bandt9299]

This is one thing I can never figure out, just when I up my sparge a little I come in way over, yesterday I brewed and the temp never got over 30 degrees and I lost the normal amount to evaporation, start with 7 or so gallons end up with 5.5 to the fermentor. I think in my beer notes I'll start writing in temperature, wind, dewpoint and humidity. Now thats a beer geek!!!

 

[bnutting]

This is one thing I can never figure out, just when I up my sparge a little I come in way over, yesterday I brewed and the temp never got over 30 degrees and I lost the normal amount to evaporation, start with 7 or so gallons end up with 5.5 to the fermentor. I think in my beer notes I'll start writing in temperature, wind, dewpoint and humidity. Now thats a beer geek!!!

Yeah now not only do we need to be chemists and biologists but we have to be meteorologists too!

 

[ohiobrewtus]

I missed by post boil volume bigtime over the weekend because I forgot to figure in the additional boil-off. Live and learn.

 

[bnutting]

I missed by post boil volume bigtime over the weekend because I forgot to figure in the additional boil-off. Live and learn.

You'd think I would remember from last year! But I guess I must have had too many homebrews!

 

[Brewing Clamper]

Yeap, it seems counter-intuitive, but the colder it is, the lower the moisture content so it's easier for water to evaporate(that's why the fridge dries up everything). The first time I boiled outside with very low temps, I lost tons of volume.