Usually, when a jar has a label that can be removed, we soak it off so that the only label on the jar is the one where we write what food is in it now and the numbers for purchasing. That looks better and is less confusing. I just demonstrated another reason:
If a jar’s original label had metallic printing on it, and you put it in the microwave, it will give off sparks and an unpleasant smoke smell. Why would you microwave a jar? Well, if that jar is full of honey that has crystallized, a few seconds in the microwave will soften it so that you can pour it out.
But if that jar has a metallic label that you did not remove but only covered with the co-op label, this is what happens in only six seconds in the microwave:
Yikes! There was no damage to the honey, my microwave, or myself–but I wonder if whatever chemicals in the labels turned so black have created something that’s not safe to handle. I decided to use a new jar of honey in the zucchini bread (I’m revising my recipe–stay tuned!) and figure out what’s best to do about this jar tomorrow.
The Earthling's Handbook 
You can decrystalize the honey in a pot of simmering water on the stove, if you are hoping to save the honey. 🙂
After the sparking incident, both layers of label were looser, so we were able to remove the labels completely. Then I could microwave the jar and use the honey.
The only problem with placing a jar of honey in a pot of water is that, if it still has labels on, the adhesive from the labels will dissolve at least partially into the hot water and thus onto your pot. Adhesives used in food packaging can be toxic! Of course, you can wash the pot and maybe get it all off…let’s hope….
Another option is to warm the water in the microwave in a container that you’re then going to recycle, which may not be “microwave safe” but at least isn’t going to melt during this brief use–like a quart-size yogurt bucket.
Ah, I hadn’t thought about the residue sticking to the pot. I’ve run jars under hot water, too, but always feel guilty about the waste of the water…