I'm an all grain brewer, have a round igloo cooler with a false bottom. I made a pumpkin ale and mashed in at 157F. Fly sparked at 170F. My first running were 1.051 and my pre boil gravity was 1.041. After an hour boil and the wort chilled down to 80F, my pre boil was 1.043 (after calculations for temp)... HOW IS THIS POSSIBLE???
Pre-boil and original gravity the same...
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Three possibilities.
1. One or more measurements are incorrect. (Were the samples at the correct temperature for the hydrometer used?)
2. Both measures are correct and you did not boil off much liquid. This could be due to a very weak boil or boiling with the lid on (I'm sure you didn't do that though)
3. Leak from wort chiller if IC used +/- option 1 or 2
1. One or more measurements are incorrect. (Were the samples at the correct temperature for the hydrometer used?)
2. Both measures are correct and you did not boil off much liquid. This could be due to a very weak boil or boiling with the lid on (I'm sure you didn't do that though)
3. Leak from wort chiller if IC used +/- option 1 or 2
jmcquesten
Well-Known Member
It's happened to me before. Only suggestion I got was that the temperature was out of range when measuring gravity (temp has to be what hydrometer is calibrated at). How much did you lose to boil-off?
If it was a hydrometer calibration issue, both would be off.
Do you fly sparge, or batch sparge? And do you stir the runnings prior to taking a preboil reading? I've found, especially with fly sparging, that if you don't stir your preboil wort prior to reading you'll get it wrong, since you're grabbing a stratified wort. It'll diffuse to consistency over time (or be stirred as such in the boil), but I've learned as a result to take preboil with a grain of salt. I'm usually within 0.2°P (approx 0.001 SG) actual post-boil gravity from what I calculate from pre-boil, but it's the same issue as topping off with water post boil, it's hard to trust that everything is evenly mixed.
Do you fly sparge, or batch sparge? And do you stir the runnings prior to taking a preboil reading? I've found, especially with fly sparging, that if you don't stir your preboil wort prior to reading you'll get it wrong, since you're grabbing a stratified wort. It'll diffuse to consistency over time (or be stirred as such in the boil), but I've learned as a result to take preboil with a grain of salt. I'm usually within 0.2°P (approx 0.001 SG) actual post-boil gravity from what I calculate from pre-boil, but it's the same issue as topping off with water post boil, it's hard to trust that everything is evenly mixed.
Every reading will be 0.006 lower than the true value.
Sounds like the hydrometer is not the best.
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Another thing to consider is when you are trying to take a gravity measurement of hot wort, you are really trying to read a moving target. The wort is continually cooling as you are trying to get your measurement.
I use a quart canning jar with a metal lid. Stir the wort well and pull a sample into the canning jar. I have a screw on lid with a hole just big enough for a digital thermometer to fit down in. I put the lidded jar into an ice bath until it reaches the calibration temperature of the hydrometer (mine is 20C/68F) and then shake the jar before pouring into my graduate for a gravity reading.
I have not had any quirky readings since I adopted this method a couple of years ago. Cooling generally takes 10 to 15 minutes, during which I am doing other things.
I use a quart canning jar with a metal lid. Stir the wort well and pull a sample into the canning jar. I have a screw on lid with a hole just big enough for a digital thermometer to fit down in. I put the lidded jar into an ice bath until it reaches the calibration temperature of the hydrometer (mine is 20C/68F) and then shake the jar before pouring into my graduate for a gravity reading.
I have not had any quirky readings since I adopted this method a couple of years ago. Cooling generally takes 10 to 15 minutes, during which I am doing other things.
Was that AT the reference temperature (common reference temps are 15C/59F, 15.5C/60F, or 20C/68F, it should say on your hydrometer)? If it's at the appropriate temp it means you're reading low and need to either add 0.006 to every reading, or you can actually adjust the hydrometer (there's instructions online for various things you can do if you google it, or probably something if you search HBT).
