In my previous post, Tamper Proofing a Bottle Cap, I mentioned that a bottle crown or tansan is very hard to tamper. Tansan is a round tin metal, cup shaped with corrugated brim. It was the tiny version of the old batiya – a large metal basin for laundry purposes.
Every tansan has a thin plastic underneath. The plastic serves as seal between the metal and bottle brim. It prevent the entry of foreign matters, spilling of liquid contents and escape of carbon dioxide – in soft drinks.
The last time, uncle and peer bought a case of solo beers. They noticed a weird taste and aroma. They examined other beers and found out the crowns were tampered. Someone else consumed the beer, replaced it with unknown liquid and put the crowns back. Liquid were dripping when the bottles were held up side down.
To make the plastic seal sit perfectly on bottle brim, an equal amount of pressure is applied toward crown top and sides. Any slight irregularity can ruin the seal. Removing the crown causes deformation. Putting it back by hand violates what I said before thus making the product leak. A tampered bottle will leak.
What if a bottle opener can remove the crown with a very slight deformation. My auntie’s wall mounted bottle opener is able to do it. The bottle opener is similar to image below. Note: illustration only, the actual steel is about 3 mm thick but of the same width.
Out of 16 used bottle crowns, 11 were resealed properly – no leaks. A single tansan endured five counts of remove and reseal. Another two performed well at second resealing. Only five failed. I pressed the sides with a vice grip and managed to get another success. Four failed and 12 success.
So a crowned bottle is not hard to tamper. Do not worry! Look for other tamper proof features. Soft drinks and beer should be bubbly when opened. A regular gin bottle has shrink wrapping. Vinegar, patis and soy sauce using gin bottle have plastic cap and shrink wrap combination. On the contrary, generic unlabeled cooking oils are doubtful.