The best product to take sticky glueness off anything is UnDu. It is what pros use to remove stuck photos from glass frames without harming the photos. I use to find it in craft stores but it's much cheaper to buy by the quart on Amazon. A quart has lasted me for four years and still have almost half the bottle left. It removes stickers or anything stuck.. If you live in CA you can't order the original and it's the best. Something has to be taken out of the original to be sold in CA. But there is another version of UnDu that can be sold in CA, it works but takes more of it. It takes off fusible from my iron like magic.
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https://www.amazon.com/Original-Form...44&sr=8-4&th=1Un-du 32 Ounce Commercial Framing Adhesive Remover