The seals for bottles with screw-on caps are commonly called shrink bands and resemble simple cylinders. Choose a seal that can slide easily over the top of the bottle while making minimal contact with the bottle. Shrink bands can be purchased online through bottling supply companies., Slide the shrink band over the top of the bottle so that it covers both the top of the bottle neck and most, if not all, of the sides of the screw on cap., Apply warm air from a heat gun set on low to the shrink band. Don't let the tip of the heat gun come in contact with the shrink band. Apply heat evenly over the surface of the shrink band and stop when the shrink band appears to be snug.
Get an appropriate seal.
Apply the shrink band.
Secure the seal.
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