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Irrenarzt 12-19-2010 03:58 AM

Stange, higher pre-boil gravity than post-boil?
 
I made a batch of blue corn maceration-free chicha today for our superbowl party from 8 pounds of crushed blue corn, 2 pounds of flaked maize and 2 pounds of 6-row (and a healthy dose of amylase powder in the protein rest and the mash, iodine test showed conversion). Everything went smoothly, as I did not make any obvious errors or blunders. Puzzling scenario however as I measured the pre-boil gravity at 1.030 at 140 F which corrected out to 1.046 on both brewcalcs and brewpal. I then did a 60 minute boil and added a pinoncillo cone during the sparge over to the boil kettle, which is 8 oz of cane sugar molded in a cone, which should in theory boost my gravity even further. I expected a higher post-boil gravity reading but got a 1.036 at 70 F which corrects to 1.037. I expected a higher post-boil gravity reading but did not get one. How is this possible?

Six_O_Turbo 12-19-2010 05:13 AM

Was your pre-boil reading cooler than it should have been?

There appears to have been an error in one reading or the other.

Irrenarzt 12-19-2010 05:36 AM

I am positive no error was made. I measured the pre-boil at 1.030 then immediately took a temp reading of 140 F. The post-boil was 1.036 at 70 F after chilling the wort, which adjusted up to 1.037. I'm pretty good about reading the hydrometer and besides, I wasn't drinking at all during this brew session ;-)

It's possible an error was made but as I recall it, I'm pretty sure I did everything by the book.

el_kirk 12-19-2010 04:48 PM

Sorry to say, I can't see any other explanation other than you made an error somewhere.
Unless you added water somewhere the OG should have been higher than your pre-boil gravity because you concentrated the sugars during the boil.
Am I right in thinking that you started your boil, took a sample to determine preboil gravity, added sugar, boiled some more, cooled and then took your sample to determine your OG? If that's right, you added sugars and removed water (unless some of your cooling water made its way into your wort?).
Perhaps the problem was that, "I wasn't drinking at all during this brew session..." Always a recipe for disaster for me. :)
Whatever you did, you at least have an OG reading.

Kirk

dcp27 12-19-2010 06:57 PM

was this pre-boil reading pre-sparge? if so, that's not that weird for it to be higher than post-boil since its a way smaller volume

jkarp 12-19-2010 07:30 PM

Quote:

Originally Posted by Irrenarzt (Post 2487485)
I am positive no error was made. I measured the pre-boil at 1.030 then immediately took a temp reading of 140 F. The post-boil was 1.036 at 70 F after chilling the wort, which adjusted up to 1.037. I'm pretty good about reading the hydrometer and besides, I wasn't drinking at all during this brew session ;-)

It's possible an error was made but as I recall it, I'm pretty sure I did everything by the book.

You can't take hydrometer readings of 140F wort. Yes, there are formulas for compensating readings for temp but they're only accurate within reasonably close ranges to the hydrometer's calibration temp.

Next time, drop your samples in a cup of ice water and take the readings when they reach the calibration temp.

trub quaffer 12-21-2010 12:41 AM

Did you stir the wort really well before taking the pre-boil gravity? I forgot to do that once and my measurements were all jacked up. Took me a while to figure out what happened.:drunk:


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