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-   -   Measuring pre and post boil volume (http://www.homebrewtalk.com/f36/measuring-pre-post-boil-volume-68983/)

missing link 06-12-2008 06:05 PM

Measuring pre and post boil volume
I've done a few AG batches and my system is pretty sound. I am having trouble with on area though and I wanted to understand what you guys do.

I sparge into a graduated bucket to measure my pre-boil volume and I also have a somewhat calibrated stick that I can insert into the boil kettle to measure volume.

Once I hit my pre-boil volume, I stop sparging and start boiling. I know that I need to boil off a certain amount. My problem is that at 45 minutes, I stick my immersion chiller into the boil and it raises the liquid level. At 60 minutes I shut off the flame but I am unable to measure my post boil volume.

When I rack off into the carboy's, I am getting more wort than I expected. I have my evaporation rate in beer smith set to 12%.

Here is my questions

1. How do you measure pre and post boil volume
2. what evaporation rate do you use to calculate boil off?


dstar26t 06-12-2008 06:11 PM

Why can't you lift the chiller for a few seconds and take a level reading with your stick?

missing link 06-12-2008 06:19 PM

I suppose I could get a glove and do that. After 15 minutes in boiling wort, the copper is to hot to touch.


dstar26t 06-12-2008 06:21 PM

Even an oven mitt would work I would assume

Alamo_Beer 06-12-2008 06:34 PM

Or you could sanitize the IC in starsan or whatever and put it in at the end of the boil.......it doesn't HAVE to go in at 15min.....

But, ultimatly the source of your problem seems like calculations....play around with your brewing software a bit more and when you brew next try and write down all of the numbers....like what all your water amounts and gravity

TwoHeadsBrewing 06-12-2008 06:38 PM

1. How do you measure pre and post boil volume
Preboil: Same as you I think...I have one of those buckets with measurements on the side, so I take one measurement of the first runnings, then add the batch sparge runnings.

Post-boil: I have marked the inside of my boil kettle at 5 and 6 gallons, using a nail to scratch it into the aluminum. I'm sure you could find a better solution, but this works for me. If I'm WAY under, I'll sparge a bit more. If I'm WAY over, I keep boiling until I hit the 6 gallon mark. Most of the time, I end up right around 5.5 gallons. The real measurement comes when I transfer to the primary...I've got that marked so I can tell exactly how much post-boil volumne I have.

2. what evaporation rate do you use to calculate boil off?
My evaporation during the spring was 9%, but my last batch was closer to 11% due to hotter/dryer weather. I assume this will continue to rise, as we get very hot, dry summer weather around here. Since I use a 7.5 gallon turkey fryer pot, I usually have too much wort to put it all in at the beginning. I'll keep the extra in a pot during the brewing process, and if my evaporation is really high I'll add some wort to the pot.

I know my methods are pretty un-scientific, but I find that measurements of water...both in the mash and in the boil, are hard to pinpoint. There are just too many variables; grain types, grain amount, mash step length, humidity, ambient temperature, etc.

Alamo_Beer 06-12-2008 06:43 PM

Yeah, lately for 5gal batches w/10lb of grain I've been mashing w/3gal and sparging w/6gal. 6gal is really too much but it's good bc I just keep running off until I have how much wort I want in my pot and the rest stays in the MLT. It makes it easier to dumb out the spent grain bc there is about a gallon or so of water in there to swish around.

For preboil I go up to ~6.5 gal if I'm boiling for 60min or 7gal for 90min. 7gal is right at the studs for my kettles handles....6.5 is about a half inch or so below...yeah I know really accurate :D

Beerthoven 06-12-2008 06:45 PM

I ferment in a graduated bucket. I use the same bucket to measure the pre-boil volume. Hence, I always have consistent pre- and post-boil volume measurements. After that its just a matter of calibrating BeerSmith with the correct evaporation rate. Mine is set at 20%. I hit my target pre- and post-boil volumes almost exactly every single time.

missing link 06-12-2008 07:12 PM

My only other question then is how do you guys handle the displacement of the chiller? Or are you using a plate chiller or counterflow where there is no affect on your volume readings?

Maybe I'm over complicating things. Next brew I'm going to put the chiller in a hot star san solution and just let it sit until I am done boiling or try lifting it out of the boil pot.

The boil is my only variable that I haven't nailed down. I am getting pretty consistent efficiency out of my electric RIMS system and I have a new burner that can boil 10 gallons much better.

Thanks for the feedback


GilaMinumBeer 06-12-2008 07:15 PM

I tend to not be concerned about the volume. There are just too many variables to deal with to nail it everytime. Sure I anticipate evaporation (1G/H Summer, 1.5-2G/Hr Winter) but never check it prior to going into the fermenter.

Instead, I monitor gravity with my refractometer and I boil until I either hit a 60 minute minimum or I keep going til I get to my target gravity.

On the rare occasion I find that my fermenter is low in volume, well then I decide if I want to dilute and lower my gravity. On the typical brewday I am a gallon or 2 over my final volume and that wort gets canned for starters (most likely) or chucked into a jug and fermented with an experimental yeast, late addition (fruit, sugar, etc...), or a wild fermentation temp (rocket fuel).

The latter I find to be the most fulfilling as it afford some playfullness without the potential of sacrificing a full 5 gallons. If I like the end result then I can tweak it a bit and go full volume.

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