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General Category => General Homebrew Discussion => Topic started by: thirsty on July 10, 2013, 01:23:10 AM

Title: Science question
Post by: thirsty on July 10, 2013, 01:23:10 AM
I have a 5 gal batch in the fridge fermenting. I also have a bunch of commercial beer bottles in there. If I turn the temp down to 38, why did I find a chunk of ice floating in my 5 gal batch, but the bottles in there did not freeze first. I am confused.
Title: Re: Science question
Post by: fmader on July 10, 2013, 01:50:54 AM
I would say your temperature controller is not working properly in order to get ice floating. I wouldn't think fermenting beer would freeze at 38 degrees. But to try and answer your question, if your beer is still fermenting, you're alcohol content wouldn't be as high as it is in the commercial bottles, therefore being more prone to freezing. I don't know if this has any impact, but your commercial bottles are under pressure too.
Title: Re: Science question
Post by: dmtaylor on July 10, 2013, 02:03:01 AM
Frank is right.  Finished beer has more alcohol, and it is under pressure.  Both will impact the freezing temperature.  Also every refrigerator has warm and cool spots.  The thermometer is probably wrong for one thing, and for another thing, the temperature is not exactly 38 F or 32 F at every single point in the refrigerator but rather only where the sensor is.
Title: Re: Science question
Post by: cornershot on July 10, 2013, 11:14:04 AM
I have an upright keezer that holds 5 kegs and I keep the temperature at 40f. I recently had a 3.8% ordinary bitter, stored against the back wall, freeze slightly. The 5% beers next to it didn't freeze. Moved the bitter to the front and the problem went away.
Title: Re: Science question
Post by: piszkiewiczp on July 10, 2013, 12:52:07 PM
Location in the refrigerator can have a large affect on local temperature. Depending on design, cold may be blown in or circulate by gravity from the freezer compartment through one small vent. If your fermenter was in the direct path of the cold, you would get some icing in one area while the liquid at the bottom of the fermenter was relatively warmer. I've heard of using a computer muffin fan in refrigerators or keezers to equalize temperatures.
Title: Re: Science question
Post by: tomsawyer on July 10, 2013, 02:27:41 PM
Sounds like your thermocouple was reading the temp near the bottles, and maybe the larger vessel was already at temp.  Usually I have th opposite problem though.
Title: Re: Science question
Post by: thirsty on July 10, 2013, 06:57:24 PM
Hey thanks for the input everyone. I think next time I just wont turn the temp down so low.