We all brought leftovers in cardboard containers. Have you ever thought about putting cardboard in the microwave for tomorrow’s lunch?
Microwaves are made to make our life easier. Within a few seconds or minutes, it’s all done to heat up or even cook some meals. However, with all these comforts, there is still a confusion about reheating the food in cardboard containers.
Does cardboard catch fire in the microwave?
Yes, it is possible for the cardboard to catch fire in two cases:
- If the cardboard box is empty. The moisture content will dry quickly and catch up the heat inside a microwave. It leaves the combustible material of cardboard to increase the stimulation
- If you leave the cardboard box for too long in the microwave. Keep in consideration that overheating cardboard raises the temperature that causes overdrying the fibres that increases the flammability.
Can you put cardboard or pizza boxes in the microwave?
If the cardboard container has no plastic coating, then yes, you can put it in the microwave. Moreover, if the container does not have any metal, glue or wax coating or plastic, you can use it safely. Stricts supervision is required when the cardboard is inside the microwave to avoid overheating.
The pizza boxes are made to store food but you should not heat it to high temperature. This also applies to take out boxes, lasagna trays or burger boxes. basic concept of how microwaves work is, it produce electromagnetic waves of a specific wavelength. The radio waves are absorbed by the moisture in the food that builds up energy in water molecules. These molecules start moving and interact with each other to produce heat that ultimately warms the food or drink. The moisture content of packaging cardboard is around 8%. That’s the reason it dries up quickly in the microwave.
When is it safe to microwave cardboard boxes?
Microwave safe cardboard boxes are made from wood fibre or pure cellulose. Generally, they’re labelled as micro- safe or contain water, coffee or food. If it is not listed, the best way is to transfer the food or drink to another container before heating.
If you put drink or any food inside the cardboard, most of the microwave gets absorbed by the item with higher moisture content. Reheating food or in cardboard containers is generally safe but cooking or boiling must be avoided.
When is a cardboard box in the microwave unsafe?
Heating the cardboard box in microwave is considered unsafe in following conditions:
If the boxes empty
As mentioned above, the moisture in cardboard is 8%. It leaves the combustible material of the cardboard to dry that can spark fire.
If the cardboard contains
Glue: If the cardboard container has glue, it would be best to avoid microwaving. Heating the glue not only produces that toxic fumes but it also melts the form that can mix into your food.
Wax or plastic: Some cardboard boxes are coated with a shiny layer of wax or plastic to make them durable. If the label says it is unsafe, don’t microwave the box as it can melt and deposit chemicals into your food.
Metal: Some cardboard boxes use metal to seal up their seams. Generally, Aluminium foil is used. In such cases don’t use the container in the microwave as the metal can damage the appliance and also cause fire hazard. If you see flame, shut off your microwave immediately
Ink and die: If your cardboard has micro- safe ink or die, you can use it but it should be labelled on the container. Otherwise avoid microwaving it because some types of ink produce toxic gasses.
How long can you microwave the cardboard box?
Overheating can be serious for cardboard. Therefore, keep the time minimum as much as you can. You can keep the microwave time below 2 minutes. However, if the food still needs heating, take 20-30 second intervals and give rest between each heating process round. Choose a low power setting because overheating is not a great option.
Essential safety tips to microwave cardboard boxes
Here are some significant tips that can help you stay safe while using cardboard packing to warm the food
Check the labelling
Most food items in packaging containers have labels. Some packaging materials don’t have information about using a microwave. However if you’re in doubt, it would be best to use an alternative method to heat your food.
Avoid free heating
Cardboard material has less humidity when placed under the microwave. It drops the level up to 1% and becomes hot. As a result, the container can catch fire. It you heat the food at low heat it will maintain the humidity level.
Check the duration
Heating food using a microwave requires no more than 2 minutes. But if you intend to take it longer, you can result in burning the container or food.
Layer your food
It would be best to protect the food from getting into contact with heat. You can use a napkin or paper towel by layering between the food and container. It also protects the cardboard from exposure to food and oil
Stay clear of glue and ink
The food box is coated with glue or chemicals and it absorbs in your food when exposed to microwave heat. Ink can also contaminate your food.
Keep an eye on the food
Be observant and watch out for responsibilities and look out for unfamiliar sounds or smells. Set the temperature at low heat and give it intervals of 20 to 30 seconds.
Remove flammable materials
Material such as metallic clips, plastic lids or paper warmers should be removed before heating the meal.
Common microwave alternatives
Not all cardboard is microwave safe. Therefore, you can also use safer alternatives to ensure that your appliance and food remain unharmed.
Micro safe Paper Products: Reheating your food in the microwave is safe in microwave safe paper products. These include wax paper towels or parchment paper. These papers can also be used to wrap the food items like pastries or sandwiches to retain moisture during reheating.
Glass ceramic: Glass ceramic cookware is safe and durable for microwave ovens. The cookware is made by combining glass with ceramic to create highly resistant material. These are perfect for reheating food in the microwave and allows the heat to pass evenly. It also minimises the risk of overheating food.
Oven cooking bags: Oven cooking bags are used for roasting in conventional ovens as they are microwave safe. The bags are made from BPA- free plastic and designed to trap the steam which helps in heating the food evenly. Using oven cook bags heat the food quickly without making it soggy.
