Simple tips on using shrink wrap seals
Choose a seal that is slightly wider than bottle cap. Fit the seal around capped bottle. Distance between seal and cap side should be minimal. You’re going to have trouble fitting a too big seal. The top end should be higher than cap, while the bottom end should cover the protruding part of bottle finish.
The seal should be easy to remove. Have two vertical dotted lines and a protrusion which can easily pulled by hand. Marking the tear line with the word “tear here” will make it more visible. I often have trouble removing seal of soy sauce bottle. I usually use kitchen knife to pry it off.
If the budget permits, procure a custom made seals with a matching design. Company or product logo on it is an added protection. Bad guys might tamper the product, replacing it with inferior content. There is no way they can replace the broken seal.
Opening the cap means destroying the seal. See the picture below. I lifted the mineral water container cap without any damage on seal.
How can I refuse it if the seal will never be broken?
A well fitted seal has overlap over the cap and covers the protruding area of bottle finish. No wrinkles allowed. Repeat any deviating work.
In case using hot water for sealing. Place the bottles fitted with shrink wraps on water bin. Then pour a just boiled water slowly on every cap. Slowly but surely. Splashing hot water over results to improper seals.
Use of heat gun if available is recommended. Hot water sealing tends to leave water droplets underneath the shrink wrap.