The internet is full of contradicting claims on the safety of putting cardboard in the oven. Can cardboard burn in the oven? Contrary to popular belief, carboard has a much higher ignition point than 451 Fahrenheit. Paper however has a lower flash point when compared to corrugated cardboard.
Can I put cardboard in the oven?
Yes. As long as there is no flame and the temperature of the oven less than 572°F (or 300°C), the carboard box and the corrugated cardboard sheet will not catch fire. Hence it is perfectly fine to reheat the frozen food at your electric home oven unless there is warning on the box.
Cardboard Ignition Temperature
What is the burning temperature of cardboard?
According to a document by Federal Aviation Administration Fire Safety the surface temperature at ignition for cardboard box is in the range of 1000 -1380 °F. The German Transport Information Service website GDV says the fire point for corrugated board is 496 Fahrenheit (258° Celsius)and the ignition point is 800°F (427°).
While in theory, the cardboard would not ignite if it stays under this temperature. However, as a rule, we do not recommend putting cardboard in the oven.
Will Paper Catch Fire in the Oven?
As you can see from the above chart, paper has a much lower temperature of ignition. Paper (not carboard) has a flash point close to 450 degrees Fahrenheit. This is especially true if the paper is too thin.
Once placed in a hot oven, it would only take a few moments for a sheet of thin paper to ignite.
Can You Put Frozen Pizza Cardboard in the Oven?
Frozen pizzas often come with a small cardboard disc that acts as a base. Placing the frozen pizza on the cardboard base will not initially cause a fire. As the pizza is directly on top of the cardboard, there is no direct contact with the heating element. The placement means that the cardboard will not react like it would with an open flame. However, if you leave it on for too long, the rise in oven temperature will increase the risk of combustion.
If you ask your friends and collogues, you can find many people claiming that they have safely cooked frozen pizza with cardboard while other will warn you that doing so can always run the risk of a kitchen full of smoke or even a fire. Despite these claims, corrugated cardboard that you find in pizza boxes will not catch fire easily.
However we do not recommend putting frozen pizza with carboard into the oven for three different reasons.
- Corrugated carboard is an excellent insulator. If you put the cardboard box inside the oven, it will block the heat and your frozen pizza will not be cooked evenly.
- If you bake the pizza with carboard, the baking temperature may cause the Pizza to taste differently because of the presence of cardboard.
- Cardboard, especially the type used for pizza boxes, sometimes is a combination of paper, wax, and glue. That combination can be flammable. With just a short amount of time at a high-heat, the cardboard may catch fire. When using combustible materials in an oven, oily foods like pizza can exacerbate the situation. Oil, cardboard mixing with high temperatures will cause smoke and likely ignite
Purpose of Cardboard Base
The cardboard base that comes with frozen pizzas is specifically there to protect your pizza. An uncooked pizza is pretty delicate and requires support to stay protected. The round piece prevents damage and keeps the crust and toppings in-tact.
In addition, most cardboard bases have an anti-grease layer on the top. The layer stops the cardboard from collecting grease and collapsing. The cardboard is great for protecting your pizza in transit but not for oven temperatures. Placing this in the oven with your pizza could introduce additional chemicals that should not be mixed with your food.
Advice on cardboard packaging holds true for more than just frozen pizza. A lot of frozen foods come packaged in cardboard with plastic coverings. Before cooking frozen foods, unless stated explicitly, remove all packaging before placing it in the oven. Neglecting to do so can lead to mishaps like melted plastic on food.
Extends Cooking Time
Some of you may want to use cardboard as a way to save the time to remove the pizza from the box and placing it on a baking tray. It is also a hassle to clean the trays and cookware.
The materials and properties of baking trays help to optimize cooking times. As pizza cardboard is not created with this purpose, it slows down the cooking time.
Safe Alternatives to Cooking with Cardboard
Baking trays ensure your pizza is cooked evenly and crisp. The metal, designed to withstand oven temperatures, conducts heat and helps to achieve a uniform bake. Unlike pizza cardboard, baking trays can help achieve a crispy base below.
Casserole Dish/Baking Pan
Casserole dishes and pans can sometimes be big enough to bake a pizza within. If you don’t have a flat baking tray, this can be a good alternative.
A casserole dish is perfect for heating other frozen foods, especially leftovers or food with sauces.
Aluminum foil can be placed over the oven rack as a cheap alternative to trays and dishes. While the foil can be tricky to maneuver, it helps to bake the pizza evenly and prevents oil from dripping.
Directly on the Rack
If you find yourself without any baking materials, fear not, as some foods can be baked directly on the rack. Pizza can be placed on the rack, without its cardboard base, and cooked for the recommended time.
Additionally, any food that specifies an oven-safe container is safe to be in the oven alone. For example, foil dishes or cases can sit on the rack and withstand oven temperatures.
If cooking directly on the rack, ensure that the oven is supervised. With no tray or base, there is always a chance that oil, or toppings can drop to the bottom of the oven. If left unattended, these drips can cause smoking, or the food could burn to the oven base.
Can You Put Cardboard in the Microwave?
Typically, you can place cardboard in the microwave without any issues.
Microwaves heat foods and liquids by moving the water molecules inside at a high frequency. Cardboard does not contain high amounts of moisture, so it is not likely to heat at the same rate.
Heating food with cardboard is safe as long as you are using the instructions on the packaging.
Most cardboard tends to be microwave safe, but there are some instances where it contains additional materials. Cardboard often consists of recycled materials, and that can include metal substances. Any form of metal is harmful and dangerous when heated in the microwave.
Cardboard containers that have wax coatings or ink prints can be dangerous when heated with food. Chemicals from these additions can leak into your food, causing the food to spoil or even toxic.
We recommend that you always check the packaging advice before heating cardboard in the microwave.
Although carboard does not burn at normal oven temperatures, cooking with cardboard or packaging on your food is risky. You can however, reheat your frozen food with open cardboard box at lower temperatures. Before heating, remember to read through instructions carefully. Placing un-safe packaging in a microwave or oven can be disastrous.
The risks outweigh the benefits when it comes to baking food in the oven with cardboard. Unless it is made for oven temperatures, remove any cardboard before cooking food in the oven.