Shrinkage

[Spelt]

I stumped. I recently upgraded my kettle with the intention of doing full wort boils. I plan around ultimately arriving at a 5 gallon batch of beer. So I start with 7 gallons in the kettle. Do a 1 hour boil which typically brings me down to around 6 gallons. I bring the kettle into the kitchen and hook up my immersion chiller. When it hits room temp, I transfer. Now there just a hair over 1/2 a gallon left in the brew kettle, but there's only 4.5 gallons in the fermenter. Where in the world does that other gallon of wort disappear to. I've done this 4 times in a row and I can't figure out where it goes. Can there be that much volume contraction during the cooling of the wort? Frustrating because I have to stop, boil a gallon, cool it down, add it to the fermenter, and only then can I pitch.

[deadeye1]

What dimension is your pot? This could be causing your wort to boil off quicker. Things like this are to be expected when getting new equipment just adjust accordingly and start with 8 gallons of water. Are you shure you are ending up with 6 gallons before you chill? It's surpirsing how much a different piece of equipment can change your routine.

Cheers
Deadeye

[siwelwerd]

I've seen 4% given as a common figure for wort shrinkage due to cooling. That comes out to about 1 Litre from 6 gallons. Other than that, be sure your measurements are accurate, and that your measuring devices are properly calculated. You said "typically" you get 6 gallons post boil. Make sure it is actually 6, and that you are not overcounting by measuring after the chiller is in (a 1/2" 50 ft chiller can displace close to a half gallon).

[CRBrewHound]

As said, what are you using to measure volumes? If you ferement in pales do not trust the markings on the side of the containers. Someone in my club told me that some of them were very inaccurate. Sure enough when I checked mine against measured volumes they were off by a considerable factor. I don't know what brand my pales are would have to look closely as the markings have faded quite a bit. So get yourself a container that you know has accurate measurements and then fill your ferementers and kettles and verify the markings on your equipment.

[Spelt]

good point about the displacement of the chiller, hadn't considered that.

Its a polarware kettle which is shorter and wider than my previous kettle.

[deadeye1]

I remember when I upgraded my brew pot I had a similar problem. I went from a tall skinny pot to a short wide pot and had to ajust after the first brew in my new pot. It took me two brew sessions to adjust. I ended up using a dip stick marked in 1 gallon increments.

[Bugeater]

I had the same problem some time back when I went from a tall skinny turkey fryer pot to a wider 10 gallon stew pot. My boil off rate went from 1.0 gal/hr to 1.5 gal/hr. Had to adjust my recipes and batch size accordingly.

Wayne

[mors]

I know I get more than 1 gallon of wort boiling off over the course of an hour. Apart from hops absorbing wort and trub being left behind there is also the fact that the wort shrinks as it cools.