The Science of Bee Candy

This is not a lid on this jar, it is a sheet of crystallized syrup. The little holes are from the bees drinking through the holes punched in the lid, kind of like Eskimos ice fishing.

One of the things I do to help my bees get through the winter is to give them syrup in the fall so they can top up their honey stores before the real cold sets in when they will need to have plenty of food at hand to keep themselves warm.
I am not an expert on bees, but this is one thing I think really does help them. In the spring I check for extra honey ( hoping to harvest some for us) and I find no extra honey. Just one comb of it in fact. That tells me they needed every drop of syrup I fed them in the previous fall.
One of our problems is that I became a bee keeper on one of the worst springs for bees because of its late low temperatures and record setting rain. A record, that is, until this year.
So I have been keeping the bees supplied with syrup. It can't hurt.
One of the weird things that I have been dealing with though is that sometimes the syrup crystallizes in the jars.
I cannot figure out why it only does it sometimes. It feels like I am making the syrup the same way each time, yet about every fourth time it does this.

I suspect it has to do with SCIENCE. I found this explanation of why candy crystallizes and that helped me understand a little better what the crystallizing process is. But it only alludes to the fact that it only takes a little shock to make sugar crystallize. I have also heard that the trick to keeping sugar crystals from forming is to add an acid, like cream of tarter or lemon juice. Also crystals will not form if something comes between the molecules, like a simple molecule of corn syrup or honey.
In my search I found this cool reference from an 1888 article where readers sent in their recipes for bee syrup and what their results have been.
You will see that it is not a new topic for bee keepers and the variety of methods and outcomes they list are just as diverse as it is today.
It's amazing how something that seems so simple can get so complex.