Why is the bag inside a food box so hard to open?
After opening (and shredding) the over-glued box of cereal to prepare part of breakfast, there is a plastic bag holding the contents. When new, it is seam sealed to the extent that trying to unseal it (to preserve the bag’s integrity) requires superhuman strength.
Likewise, trying to tear the bag itself open (not at the seal) results in the bag stretching to a point, but then becoming as strong as spring steel. The result is often that it explosively tears and blasts the contents all over the kitchen.
Why is that bag so strong? Wouldn’t it be cost effective to make it, say 10% as strong AND easy opening? It will still discourage ants and locusts, and survive international shipment.
The result is that Clorox bleach is easier to open than breakfast cereal. Are we expected to use a knife or scissors?
The strength of the tubular material – which eventually forms the waxy plastic bag inside your cereal box – is dictated by the requirements of the machinery which forms the bag and fills it with cereal. It operates at incredibly high speed and the need for consistency and reliability is paramount. It is not cost effective to reduce the bag’s strength if that, in turn, results in stoppages during the packaging process. The consumer’s needs come way down the pecking order!
Incidentally, you are right to ask this question. The design of the food packaging (including the waxy bag) is constantly under review and development and mistakes are made – e.g. I remember that recently Kelloggs had to recall 28 million packs of cereal after it was discovered that the waxy bag contained unacceptably high levels of methyl naphthalene. Those of us granolas in the know get our breakfast cereal packaged in cellulose bags.
The cereal box itself is not necessarily any safer. Here in Europe the use of benzophenone in food packaging and – most recently – 4-methylbenzophenone in printing inks for food packaging of children’s breakfast cereal – has been the subject of investigation (see below).
Thanks for a great answer to my question on a solar cell for my 12V DC fan!
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