A refractometer is a great help (gotta buy one myself, one of these days), but you have to be careful with uncapped honey as a general rule.
If most of the super is capped, and the uncapped part does not shake out at all when you turn the frame upside down and shake it, it probably has had enough moisture removed from it to be ok.
Unsealed honey that is too liquid, has too high of a moisture content, will ferment, and then you've got other problems. The gas pressure generally pops the lid, or oozes out, making a nice mess. Plus the fact that the honey is basically ruined.
Regards,
Steven