Refractometer/Hydrometer/GHL

[gregzz4]

Firstly, I wouldn't worry about the hydrometer reading as they cannot always be trusted ( put it in a drawer and forget about it )
As for calibrating the refractometer;
Mine requires me to have the solution @ 68f. I take a digital thermometer with me and wander around my basement until I find that room temperature. Then I put a drop on the lens and wait a couple minutes for it to equalize before I close the cover. I've never had an issue with it when I do this.