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 Post subject: Evaporation Rate Question
PostPosted: Wed May 17, 2006 3:03 pm 
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Ok, sunday after Ray Daniels, there was a discussion around Justins Evap rate. I have a question regarding my technique. What I do is boil the wort as usual, around the time I do my 15 min. additions, I'll guestimate how much volume I lost and just add some more to get to my target post boil volume. It knocks down the boil for a second, but I start the timer again once it starts boiling.

I haven't noticed any issues as yet, and it is much easier for me to do this then calculate my evap rate for every season.

Comments?


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 Post subject: Re: Evaporation Rate Question
PostPosted: Wed May 17, 2006 3:55 pm 
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[quote="4nier"]Ok, sunday after Ray Daniels, there was a discussion around Justins Evap rate. I have a question regarding my technique. What I do is boil the wort as usual, around the time I do my 15 min. additions, I'll guestimate how much volume I lost and just add some more to get to my target post boil volume. It knocks down the boil for a second, but I start the timer again once it starts boiling.

I haven't noticed any issues as yet, and it is much easier for me to do this then calculate my evap rate for every season.
[/quote]

He talks about doing this in his book, they are inverse operations, gravity units will remain almost the same throughout your boil. But according to his book you should be more concerned with your final gravity. Who cares if you got 5g of wort if its at 1.020 when it should have been 1.040, if you dont have the right specific gravity the beer probably isnt gonna be that great (probably too watery).

If you know your evap rate and know your shrinkage, you should be able to always hit your target gravity by using the correct volumn at the start of boil. This is one of the many reasons why a lab book is so useful. He has a great water calculation at the end of one of the chapters that really makes it too easy.

Mr. Cheese


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PostPosted: Wed May 17, 2006 4:02 pm 
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4nier, I do this every batch. I have a wide copper kettle and my evaporation rate is huge. I have to add 3 gallons of water to the kettle before the boil to come out near my target. I always check before I add my flavor hops so that I finish on time and on target.


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 Post subject: Re: Evaporation Rate Question
PostPosted: Wed May 17, 2006 4:16 pm 
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Mr.Cheese wrote:

He talks about doing this in his book, they are inverse operations, gravity units will remain almost the same throughout your boil. But according to his book you should be more concerned with your final gravity. Who cares if you got 5g of wort if its at 1.020 when it should have been 1.040, if you dont have the right specific gravity the beer probably isnt gonna be that great (probably too watery).

If you know your evap rate and know your shrinkage, you should be able to always hit your target gravity by using the correct volumn at the start of boil. This is one of the many reasons why a lab book is so useful. He has a great water calculation at the end of one of the chapters that really makes it too easy.

Mr. Cheese


Just to clarify, I do TRY to hit my evap rate. I use the stock calculation out of BeerSmith. At 15 minutes till the end, If I am below my target post-boil volume I add water.

I guess I was just confused as to the whole worry about it when this seems to be a simple solution.


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PostPosted: Wed May 24, 2006 8:40 am 
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4nier, to really get a good hold of your evaporation rate, you're going to need some way of determining you pre and post boil volumes. Some people use a graduated stick, spoon, or metal rod. I use a sight glass that I calibrated to the quarter of a gallon, so that when it says 10.25 gallons *hot*, I know it will be 10 gallons *cold*. With this information, and knowing how long I need to boil (90 minutes minimum) I usually collect 14 gallons of wort, and boil for 120 minutes, or I'll collect 13.5 gallons, and boil for 90 minutes, depending on the type of beer I'm making. This works out to 1.75 to 2 gallons per hour, and is primarily a function of how much thermal loading I put into the kettle (another variable that you need to figure out). So I basically have a 12~15% evaporation rate, which is about as high as you would want to go, given all other considerations posted previously.

Prost!

Michel


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 Post subject: Re: Evaporation Rate Question
PostPosted: Wed May 24, 2006 8:52 am 
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Location: Pepperell, MA
4nier wrote:
What I do is boil the wort as usual, around the time I do my 15 min. additions, I'll guestimate how much volume I lost and just add some more to get to my target post boil volume. It knocks down the boil for a second, but I start the timer again once it starts boiling


I haven't listened to the Ray Daniels show yet, but I do the same as you do. Since I'm brewing 5.5gal AG batches with a 30qt stainless steel turkey fryer pot, I have to stop sparging at 24L (little less than 6 gal). At the end of my boil I always have to add water to hit my post poil volume and gravity.

Shortly before I place my immersion chiller in the pot, I'll kill the heat so the bubbling stops and I can read the current kettle volume. Then I add the chiller and turn the heat on again. Now I can calculate the amount of water to add. But I add boiling water. This will not interrupt the boil. But the main reason for boiling is the fear of hot side aeration which could happen when I add oxygen with the cold water.

Should I be afraid of HSA when I would add cold water?

Kai


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 Post subject:
PostPosted: Wed May 24, 2006 10:08 am 
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Should I be afraid of HSA when I would add cold water?

In a word, no. Use deaerated water if you are concerned, but unless you are adding enough tap water to affect temperature into the alleged HSA range, then you really don't have a problem. You *really* have to abuse your wort to cause HSA anyways from experiments that I've done, but as usual, ymmv. Ttyal, and ilbcnu!

Prost!

Michel


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