how do you remove hand warmers

I need to replace the handlebars and I want to remove the hand warmers without ruining them so I can reuse them. I used the air method to remove the grips, but the hand warmers are still wrapped tightly around the bars ( looks like they are glued on). Any ideas, as I don't want to damage them, they look fragile.

Thanks, any help would be greatly appreciated:)

I've used razor blades, just becareful and take you time, then use grip glue to reattach

Thanks for the reply. What I did, was use a heat gun to soften the glue so I was able to peel them off without harming them. It worked just fine and I was able to reuse them.

Thanks again