Refractometer and hydrometer question

In a recent post it was pointed out that Mash Efficiency and Brewhouse Efficiency were important in determining residual volumes. 

https://www.youtube.com/watch?v=bIoeFuNbDbU  good tutorial, at least for me regarding the two values.

The question is in measuring the pre-boil gravity what are the temperature tolerances for a 'typical' hydrometer.  Will a 150 degree sample be acceptable for the hydrometer or will it shatter?  I understand that the reading must be temperature compensated, my concern is the equipment durability. 

Hydrometers and refractometers are meant to read at room temperature.

Refractometers require a very small amount of wort, so the cooling is just seconds.

I doubt a hydrometer would shatter at mash temperature, but the further you get from calibration temperature the less accurate the adjustment tables tend to be. Since it makes sense to take your readings at a lower temperature, why not do just that.

It might not shatter, but it might be ruined. Most float hydrometers are glass tubes that have some steel shot held into the bottom with wax. The manufacturer can add shot beads until the correct level of flotation is achieved. If you put the float into water that is hot enough to melt the wax you can alter the balance of the device and ruin its calibration. My hydrometer is calibrated at 68 F and has temperature corrections listed for 54 - 84 F. I don't like to rely on those and try to take measurements on wort that is close to 68 F. For mash, it isn't much harder to cool to 68 that it is to cool to 84, so I wait the extra time (using a metal cup in a bath of ice water).

--GF