I take a hydrometer sample while coming up to boil. My flask is plastic. I put it in the freezer and it normally cools to ~60F when the boil has reached 15 minutes in that way I don’t have to rely on the adjustment calc. My process is close enough that I don’t need a reading sooner because I’m rarely off a point or two.
Thanks for this information. Yes, my hydrometer is calibrated at 60F and I have verified it several times. I use a plastic flask and distilled water for calibrating.
I have a hydrometer (https://www.morebeer.com/products/triple-scale-hydrometer.html) that is calibrated at 68 F. My wort and ale spend a lot more time closer to 68 than to 60, so I like this a lot. I agree with Denny that I don’t trust the temperature corrections very much, so I prefer to get my samples as close as possible to the calibrated temperature.