Hydrometer Calibration

I am prepping for my first brew in 10 months. I expect to make some mistakes and run into some speed bumps, so I'm doing most of the prep a day in advance. One thing I decided to do is check the calibration of my refractometer, hydrometer, and thermapen. The thermapen and refractometer needed essentially no adjustment. The hydrometer was a bit off.

I sampled distilled water at 68*F. My hydrometer claims to be calibrated for 60*F. It read 1.003 and according to the beersmith adjustment it should read 0.999.

Now I could just subtract 0.004 from any reading, but it also occurred to me that I could just find out what temp my hydrometer is really calibrated for and enter that into beersmith.

To do this, I put my hydrometer in warm water and saw a reading below 1.000 as expected. I allowed the water to cool until the hydrometer read 1.000, and used my thermapen to learn that my hydrometer is calibrated for about 89*F. I was able to verify this using beersmith by entering a measured gravity of 1.003 at 68*F and adjusting the calibration temp until the actual gravity read 1.000. This occurred between 87*F and 91*F.

And wouldn't you know it, I went to recal my refractometer now...Hydrometer read 1.037 @ 84.5*F, corrected to 1.036. Refracto read 9.0 Brix which gives a brix correction factor of 1.00000 according to beersmith. Hot damn!

yea im having the same problem with my hydrometer. i just found out its not even calibrated properly. mine is supposed to be calibrate to 68 like yours. but instead of sitting at 1.000 it sits at 1.006! I have been just subtracting the .006 from all of my readings but you make an interesting point about finding the TRUE calibration temperature.

But i dont understand why they dont just sell the hydrometers and say " hey not all hydrometers are calibrated equally, so find out what yours is calibrated too, so you actually can know what your doing!".