The bag we bought was bigger than the typical 34g packet costing 60p. Five years ago, the standard bags were 35g and cost 42p.

The cushion actually is nitrogen gas. Chip manufacturers fill bags with this preservative gas to help keep chips fresh. If it were filled with regular air, the chips would likely turn soggy and spoil.

Manufacturers claim the space left in crisp packets is needed to help keep them fresh. Most bags of crisps, including all the ones we tested, are filled with nitrogen gas to fill packs which keeps the contents fresh and crunchy.

Packet of crisps weigh 27 grams each.

In 2015, visual artist Henry Hargreaves conducted a similar experiment. His finding found air comprised about 70% of the bag, compared to the group’s finding of an average air amount of 43%. This means a 27% increase in the amount of chips in the bag in the past two to three years.

The chips that offered the best bang for the buck were Fritos, Pringles and Tostitos. They had the highest chip-to-empty-space ratio, with air percentages ranging from 34 percent to just 19 percent in a Fritos bag. “It’s best to consider the average at 43 percent,” Kitchen Cabinet Kings said in a press release.

nitrogen gas

But it is the first time we’ve noticed something funky on their packaging. On the back of the one-ounce bag of chips, a bold warning reads, “Consuming this product can expose you to chemicals, including acrylamide, which are known to the state of California to cause cancer.”

The basic material is BoPET, otherwise known as Mylar in America. Adding a thin layer of aluminum makes the bag much less gas permeable, and also shiny. It keeps the food fresher longer by keeping out oxygen better than plastic does. Chip bags are filled with nitrogen so that there is little oxygen to begin with.

In the likely event your Earth911 search comes up dry or your curbside program doesn’t accept them, you do have one option: TerraCycle offers a mail-in recycling program, which collects everything from individual snack bags to those family-sized chip bags to be recycled into hard plastic.

Place your empty chip bag in the microwave. Heat it on high for NO LONGER than four seconds. If you heat it any longer, you could damage the microwave oven. You should have seen some fireworks in your microwave oven from your chip bag.

What’s happening: Polymers, or long chains of molecules, make up the plastic that makes up the bag. When the bag is heated in the microwave these polymers return to their natural tendency and clump up again.

In crisp packets, these polymer chains are stretched out straight. When you heat up the crisp packet, the polymer chains start to get more energy. This makes the polymer chains vibrate and start curling up. The wrapper seems to shrink because all the polymer chains have curled up over each other!

When a bag of chips is made, these polymers are heated and stretched out to make the flat material used for chip bags. The high heat of this process locks the molecules in this “stretched out” state.

Never try microwaving cold chips, Magda says. Potatoes retain moisture that comes out when they are reheated, and if they’re in a microwave or a conventional oven, that steam can’t escape. Sealing them tightly can cause bacteria to grow, and you don’t want a side serving of that with your chips!

What to do:

1. Preheat your oven to 100 degrees Celsius or 200 degrees Fahrenheit.
2. Wash your empty chip bag gently with water and dry with a towel.
3. On a baking tray, lay your chip bag flat between two sheets of baking paper.
4. Place the baking trays in the oven for about 10 minutes.

Explain what happens to a potato chip bag as it warms in the heat of the sun. As the bag warms, the particles of air inside the bag begin to move more quickly and bounce into the sides of the bag, causing the bag to expand. As a gas cools, its particles move more slowly and come closer together.

Shrinking chip packets in the oven or microwave was almost a right of passage. So much so, we’d turn them into keyrings and hang them off our school bags, just to prove we had successfully done it. From Twisties to Doritos, you name it, we shrank it.

Put the chip packet on top of a sheet of baking paper on a tray. Place a second sheet of baking paper over the top. Bake at 180°C for 10 minutes. Remove the top baking tray, wait a minute for it to cool slightly and remove the chip packet.

For anyone that wants to shrink their crisp packets here is how it is done: Preheat the oven to 175 degrees (without the fan if possible) Place the crisp packets on the tray and then place in the oven. Watch as they miraculously start to shrink (you think nothing is happening and then POW all of a sudden they start)

How do you wash a crisp packet? A. You can either wash them in warm soapy water then hang out to dry or towel dry.

Two of these are polystyrene, the material in foam cups and plastic food containers, and the other is polyester, from which soda bottles are made. You can make your own shrinking polymers by baking polystyrene in a regular oven!

No matter what kind of plastic you are using, don’t use it for oven use. It will melt from the inside or it might melt completely. For safer use, don’t use plastic ’cause your oven might catch on fire.

Can plastic fumes contaminate food? Those fumes can kill; they can also contaminate food. Any type of food stored in permeable packaging — cardboard, plastic wrap, etc. Toxic fumes can permeate the packaging and contaminate the food.