Thermo-Tec Sound/Heat Barrier Not Very Sticky Any Longer

I purchased two three foot by five foot rolls of Thermo-Tec a couple of years ago for the '65 Formula S. Installed it this week. I did not have to peel off the waxy protective film, it just fell off. The sticky black surface of the product must have been exposed to the atmosphere for a while and is not super sticky like it is when new/fresh. This made it very easy to move around during installation, but at the same time, has me wondering if it will have more of a tendency to fall off later. I am hoping the rolling and pushing will be enough to encourage it to not fall down in the future on top of the headliner. I hated to throw it out after the expense of purchase, shipping, and customs charges.

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