Gravity Difference pre vs. post chilling. - Home Brew Forums

Register Now!
Home Brew Forums > Home Brewing Beer > All Grain & Partial Mash Brewing > Gravity Difference pre vs. post chilling.

Reply
 
Thread Tools
Old 01-10-2011, 06:34 PM   #1
hedonist91
Recipes 
 
Sep 2009
Poughkeepsie, NY
Posts: 71
Liked 4 Times on 3 Posts



Hey everyone, anyone run into this phenomena?:

I'll take my refractometer reading just after creating a whirlpool and letting it settle, while the wort is hot in the boil kettle, and I'll get say, a gravity of 23. I send it through the plate chiller and the gravity is 17.5.

Is this a plate chiller issue ie. we're taking particles out of the wort, is it a cold-break issue?

We've tested it against a hydrometer sample that has been taken out of the hot side and chilled in an ice bath, vs a hydrometer sample that has come out of the plate chiller and get the same results as the refractometer readings.

Thanks

 
Reply With Quote
Old 01-10-2011, 10:03 PM   #2
TheMan
HBT_SUPPORTER.png
 
TheMan's Avatar
Recipes 
 
May 2009
Illinois
Posts: 3,045
Liked 340 Times on 252 Posts


Even if the refractometer is ATC you still need to let it sit for a few minutes at room temperature before checking the gravity. I'm guessing this is the issue.

 
Reply With Quote
Old 01-10-2011, 10:06 PM   #3
AZ_IPA
PKU
HBT_LIFETIMESUPPORTER.png
 
AZ_IPA's Avatar
Recipes 
 
Jun 2008
The Cold Part of AZ
Posts: 52,673
Liked 8718 Times on 7006 Posts


Leak in the plate chiller that is diluting your wort with chill water?

 
Reply With Quote
Old 01-10-2011, 10:22 PM   #4
lamarguy
 
lamarguy's Avatar
Recipes 
 
Aug 2008
Austin, TX
Posts: 1,653
Liked 25 Times on 24 Posts


Quote:
Originally Posted by AZ_IPA View Post
Leak in the plate chiller that is diluting your wort with chill water?
That would quite a leak to go from 1.096 to 1.070.

I vote - (1) not properly cooling the sample to room temperature or (2) selecting a turbid sample. Selecting a sample with visible hot break can cause off readings.
__________________
Doggfather Brewery

Planned: Lambic, American IPA
Fermenting: 6 gals of 1.090 stout (Belgian) & 6 gals of 1.090 stout (English)
Tapped: Berliner Weisse, Black English IPA, German Pils, & Live Oak Primus

 
Reply With Quote
Old 01-11-2011, 01:04 AM   #5
hedonist91
Recipes 
 
Sep 2009
Poughkeepsie, NY
Posts: 71
Liked 4 Times on 3 Posts


Quote:
Originally Posted by lamarguy View Post
That would quite a leak to go from 1.096 to 1.070.

I vote - (1) not properly cooling the sample to room temperature or (2) selecting a turbid sample. Selecting a sample with visible hot break can cause off readings.
the numbers I used were just random numbers I chose to illustrate better what I was saying-but yeah it does make sense what you're saying about hot break.

I do see floaties in the hot sample, i try to avoid them to no avail, they're pretty much homogeneously spread out throughout the boil kettle-but they don't make it to the fermenter.

I was leaning towards this too-thanks.

I'm still sort of baffled as far as hitting similar efficiency marks with my system-I get really consistent 80 percent efficiency with about half of my recipes, but not so much with others. I understand with a big grain bill I'm going to get lower efficiency unless I decrease the water to grain ratio in the mash, or sparge longer, and boil longer to increase the amount of extract yield, so it doesn't really bother me that with different brews my efficiency is slightly off.

It just bugs me that post-sparge I get one number, before boiling,and so I scale down the volume to see what the gravity is going to be using beersmith. Then the gravity is way more than what I think it would be after boiling(flawed logic perhaps using apparent efficiency pre boil to estimate it post boil?). Then, post-chill, I get numbers lower than what I think it should be.

The erratic gravities are frustrating with new recipes, in estimating what the OG we're going to hit is. Once we get a certain result however, it repeats with the subsequent brews of the same recipe.

Brewing = trial and error, but really fun trial and error.

 
Reply With Quote
Old 01-11-2011, 01:07 AM   #6
hedonist91
Recipes 
 
Sep 2009
Poughkeepsie, NY
Posts: 71
Liked 4 Times on 3 Posts


Quote:
Originally Posted by TheMan View Post
Even if the refractometer is ATC you still need to let it sit for a few minutes at room temperature before checking the gravity. I'm guessing this is the issue.
I thought of this too, and waited to check the reading, no dice. Thanks though -I wish that was the issue!

 
Reply With Quote
Old 01-11-2011, 01:29 AM   #7
Frodo
Recipes 
 
Nov 2009
Petersburg, AK
Posts: 1,034
Liked 28 Times on 27 Posts


Theoretically the floaties should not skew the reading, but just make the blue/white line hazy since the refractometer is supposed to measure dissolved sugar using refracted light. Chunks don't refract light AFAIK. However, since the protein that will become cold break material is still dissolved in the wort when it's still hot, maybe it bends the light some too throwing the reading off. That doesn't seem to make sense though since you got the same results as the refractometer with a chilled down hydrometer reading... in that case the cold break material should have coagulated in the sample jar and wouldn't be dissolved anymore either. And when the few drops hit the glass on the refractometer it should have a mini-cold break right? Interesting for sure.

 
Reply With Quote
Old 01-11-2011, 01:47 AM   #8
hedonist91
Recipes 
 
Sep 2009
Poughkeepsie, NY
Posts: 71
Liked 4 Times on 3 Posts


Quote:
Originally Posted by Frodo View Post
Theoretically the floaties should not skew the reading, but just make the blue/white line hazy since the refractometer is supposed to measure dissolved sugar using refracted light. Chunks don't refract light AFAIK. However, since the protein that will become cold break material is still dissolved in the wort when it's still hot, maybe it bends the light some too throwing the reading off. That doesn't seem to make sense though since you got the same results as the refractometer with a chilled down hydrometer reading... in that case the cold break material should have coagulated in the sample jar and wouldn't be dissolved anymore either. And when the few drops hit the glass on the refractometer it should have a mini-cold break right? Interesting for sure.
Next time I brew I'll make a thread about it, I don't have exact numbers to give that would make this a more adequate discussion. I'll take pictures so we can examine it further. I'm interested too, maybe the numbers are off in my head. I'll have to treat it like a legit experiment with legit observations.

 
Reply With Quote
Reply
Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
Post boil gravity lower than pre boil PolarisSnT All Grain & Partial Mash Brewing 10 06-15-2011 08:04 PM
Post-boil gravity was high. Not sure why. Can you guys help me troubleshoot? headwall All Grain & Partial Mash Brewing 8 03-10-2010 11:46 PM
Calculate Gravity Post Boil? JMSetzler All Grain & Partial Mash Brewing 3 11-23-2009 12:35 PM
Post boil gravity doesn't match post boil gravity Kaiser All Grain & Partial Mash Brewing 17 02-10-2009 04:07 PM
Post Mash Gravity using Beer Smith jzal8 All Grain & Partial Mash Brewing 3 12-28-2007 04:12 AM


Forum Jump