24% Evaporation Loss

Just moved into my new apartment and decided to get my numbers for my new brewery.

So I filled my brewpot up with 4.5 gallons of water and let it come to a boil (actual water temp was about 208 degrees), then timed it for exactly 1 hour full boil.

I let the water cool off overnight and started measuring... came up with 3.42 gallons left over. Using the equation from BYO.com:

Evaporation percent = 100 - (post-boil volume x 100 ÷ pre-boil volume)

I ended up with a Evaporation Loss of 24%. Thats a damn lot of loss. It says in the article homebrewers should expect around 6% to 8% loss.

So should boil at a lower temp???

Have any of you measured your Evaporation Loss? and if so, what is it?

Any sugestions on how to lower mine?

My evap rate is right around 25% each boil. Basically two gallons is what I boil off.


Dan

First of all, you can't lower your boil temp... the water will boil at a given temp for a given elevation. When I did my first batch I started with about 6.5 gallons and ended up with 4.75gal. So I think you're probably about right. Why are you worried about this anyway?

mykayel said:

First of all, you can't lower your boil temp... the water will boil at a given temp for a given elevation. When I did my first batch I started with about 6.5 gallons and ended up with 4.75gal. So I think you're probably about right. Why are you worried about this anyway?

Click to expand...

Yeah it's no big deal. Once you know your evap rate, you just add more water.



Dan

You may need to adjust your relative humidity.

Oh wait, we have no control over relative humidity.

Just add water.

I think Mr. Wizard slipped up on his numbers. If you are doing extract and barely keep the boil rolling, maybe. But his figures would indicate 4-5 hour boils for all-grain (7.5 gal. -> 5 gal), which is ridiculous.

A good boil only has to be strong enough that when you stir it, the boil does not stop.

It's always a good idea to have a gallon of pre-boiled and cooled water around to adjust the volume in the fermenter.

Sounds about right to me. For a 4 gallon boil, if I preboil my water 20 minutes to get rid of clorine and do an hour boil on the wort, I end up with 3 to 3.5 gallons wort when I siphon to my bucket.

I keep a couple bottles of spring water in my basement to bring it back up to 5 in the fermenter.

david_42 said:

I think Mr. Wizard slipped up on his numbers. If you are doing extract and barely keep the boil rolling, maybe. But his figures would indicate 4-5 hour boils for all-grain (7.5 gal. -> 5 gal), which is ridiculous.

A good boil only has to be strong enough that when you stir it, the boil does not stop.

It's always a good idea to have a gallon of pre-boiled and cooled water around to adjust the volume in the fermenter.

Click to expand...

I out in 7.25 gallons in my pot on my last batch and came out with about 5.20 gallons after boil. am I boiling too vigorously?


Dan

With AG the goal is to boil down 5+ gallons. How much you start with is really driven my your sparge rate: 7.25 to 5.20 is fine. I batch sparge and typically start the boil around 6.5 gallons.

mykayel said:

Why are you worried about this anyway?

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Not to worried about it, just didn't expect that much loss... After reading the article I mentioned I thought maybe at the very highest 10% loss.

Now I know and I can adjust my recipes

Craig said:

I let the water cool off overnight and started measuring... came up with 3.42 gallons left over. Using the equation from BYO.com:

Click to expand...

Craig, did you leave the lid on the pot, while it was sitting overnight? You're going to get some SERIOUS eveporation, especially in the first hour or so.

steve

I have found that most books and recipes from HBSes have boil losses at way less than actual for me. Boil loss is related to pot diameter so I can only speak for myself but I have a 32 quart megapot and do lose from 1.29 to 1.37 per hour depending on the barometric pressure,relative humidity and wort gravity. This typically equates to 1.5 to 1.6 gallons loss in my 70 minute boil.

Percentage loss is never accurate. You do not lose a percentage - you lose a certain amount per hour. I don't know who came up with this percentage per hour calculation but it is totally BS. If that were true, you could boil a quart for an hour and only lose a percentage of the quart. I can assure you that if you boil a quart in your boil pot for an hour, you will have a ruined pot.

I have kept record of my losses in my pot and calculate on the basis of 1.29 per hour which in my case is correct most of the time. You should do the same. Keep a record each time and you will soon know how much to allow for boiling loss.

skou said:

Craig, did you leave the lid on the pot, while it was sitting overnight? You're going to get some SERIOUS eveporation, especially in the first hour or so.

steve

Click to expand...

I left the lid on while it cooled.

Prowler 13 said:

I have kept record of my losses in my pot and calculate on the basis of 1.29 per hour which in my case is correct most of the time. You should do the same. Keep a record each time and you will soon know how much to allow for boiling loss.

Click to expand...

Sounds like a good plan.. thanks