We purchase the lids for the Electro-Gel jars, and they already have the paper lining and foil seal attached when we receive them. The only function of the adhesive is to hold the foil liner to the inner paper liner of the lid until the lid is placed on the jar.
The lid is applied to the jar with a sealing head. The sealing head creates an electromagnetic field which induces an electrical current into the foil portion of the liner. This seals the foil liner to the jar.
We have a new plate for the sealing head which has been cut specifically for the Electro-Gel jar(s) lid. (All sizes of Electro-Gel jars use the same size lid). It is very important with induction heating that the sealing plate be exactly centered on the lid being sealed.
The foil lining has one purpose only. We started using it to help prevent the gel from leaking during shipment. Once the gel has reached its destination, the foil lining and paper seal have outlived their purpose. Once the gel has been received by the customer intact with no leakage, the seal is no longer important to the integrity of the product.
We hope this information helps answer your customer's questions. Please let us know if you need anything further.