If something is stored inside sealed or closed paper cardboard and the cardboard is put under strong sunlight, is it usually good enough to keep the stored item cool?

In Antarctica, yes. In Sahara, no.

3 hours ago, kenny1999 said:

If something is stored inside sealed or closed paper cardboard and the cardboard is put under strong sunlight, is it usually good enough to keep the stored item cool?

Temporarily. The cardboard will heat up, and radiate into the box.

On 6/27/2023 at 8:26 PM, swansont said:

Temporarily. The cardboard will heat up, and radiate into the box.

From Google search, a number of results suggest that carboard is a good heat insulator.

14 minutes ago, kenny1999 said:

From Google search, a number of results suggest that carboard is a good heat insulator.

That’s for conduction and convection. The corrugation creates pockets of dead air, much like double-pane glass. So if you have a temperature differential, the cardboard will reduce the rate of heat transfer. But you specified sunlight, which means radiation. The cardboard will block this, but will absorb some of the light, So, as I said, it will heat up, and radiate into the box. How much depends on details that you haven’t provided.

On 6/27/2023 at 10:02 AM, kenny1999 said:

If something is stored inside sealed or closed paper cardboard and the cardboard is put under strong sunlight, is it usually good enough to keep the stored item cool?

I did my apprenticeship in a paperboard mill where we regularly ran a grade for conversion to fish boxes for storage and transport of frozen fish.

Typical product range details can be found at https://diepvriesurk.nl/en/packaging/carton-packing/

Quote

Cardboard fish boxes are made from corrugated cardboard or solid cardboard. They are specifically designed to transport frozen fish. If required, we can offer boxes with different properties related to water resistance, strength, and insulation. The dimensions of the box are adapted to the product in order to guarantee the maximum pallet load.

 

Cardboard boxes are a familiar and trusted packaging material in the fish industry. It offers several advantages:

• 100% recyclable
• Made from renewable sources
• An environmentally friendly alternative to polystyrene and styrofoam boxes
• Less transport damage thanks to strength and flexibility
• Lightweight material
• Suitable for printing (coloured) text and images
• Use to promote products and brands, and achieve your marketing objectives
• Maximum pallet load in small sales results in lower transport costs

Storing such boxes in strong direct sunlight would not be recommended. Why would anyone want to do this?

Mostly no but it can be if structured correctly. It can act as shade and if there are large openings on the sides then air circulation can cool down what’s inside. However, it will heat up like a dry sauna inside if it’s kept sealed.