pre-boil gravity measurement - cool first?

[bdaddy]

OK, I'm going to measure my pre-boil gravity this time around to hone in on my efficiency. I'm guessing my wort will be around 150-170 after the sparge...I have a wine thief and can take a sample at that time. But do can I just plop my hydrometer in at that temp and then using software to adjust the reading? Or do I need to cool my sample before taking a measurement first?

 

[Yooper]

There is a correction table, but in my experience in any sample over about 90-100 degrees, it's inaccurate. If you cool the sample to under 90 degrees first, (an ice batch in a pitcher is perfect) then the correction software works pretty well.

That's a wordy way to say, "cool it down a bit first!"

 

[BigB]

Draw a sample and cool it off. A high temperature will REALLY throw off the reading and you cannot properly adjust for it with that much deviation.

 

[ajf]

You missed to other important point.
First stir the wort really well to make sure you don't have a gravity gradient
Then cool it and take a gravity reading.

-a.