How to Make Cardboard Boxes Waterproof?

Cardboard boxes themselves are pretty vulnerable to moisture and water. Therefore, many people want to make their cardboard boxes waterproof either to save it from oil and grease in the product or the product itself is expensive and vulnerable to water. Whatever the reason, waterproofing cardboard boxes is simple and inexpensive. After doing some research, I’ve found out the multiple ways of waterproofing cardboard boxes.

There are a number of ways you can seal off elements from affecting your cardboard box. Technically, waterproofing a cardboard box is not exactly making the box waterproof but to add a layer of waterproof coating on the box. This also suggests that whatever the process, it should cover all of the boxes including its edges and corners. Being made of paper, cardboard boxes can get destroyed even if there’s a tiny untreated spot, which could soak in water.

As I said, there are a number of ways; from spraying water-resistant liquids to using tapes. You could even shrink-wrap it or use aluminum foil if you know how to! Some easier method would be to simply enclose it in a waterproof polyethylene bag; this may come in handy for a small cardboard box. You can use permanent paints such as acrylics, enamels or epoxy resin to create a layer of the waterproof surface on the cardboard box.

Here are Some Best Ways to Waterproof Your Cardboard Box

Using Waterproof Coating:

You can use polyurethane coating, or clear acrylic spray paint or lacquer spray sealer spray to make cardboard waterproof. These protective coatings are themselves harmless but should always be done in a well-ventilated space. Moreover, the coatings are flammable, which makes space ventilation even more essential.
First, put on your gear such as gloves and goggles. Prep the area by laying a sheet of plastic on the surface.
Place your cardboard box on the plastic sheet, and cover other valuables in your workspace.
Shake the can thoroughly so that the pigments are mixed well in the can. Also, shake the can periodically between application.
Hold the can 12 inches away from the box and apply a thin layer of coat running parallel to the surface of the box. Spray in a steady back-and-forth motion and let it dry for a few hours before applying the second coat.
After the surface is coated, spray small blobs of the coat around the corners and edges.
All waterproof coating has its own set of instruction, which is worth noting before treating the cardboard box.

Using PVA Glue Coat

PVA glue coat will give you a water-resistant surface if not absolute waterproofing, which is enough most everyday use. Most PVA glues are grade 2 water resistant which means it can survive several cycles of soaking and drying.

Prep the work area by spreading out plastic sheets or old newspaper on the floor. Place the cardboard box on the prepped area.
Mix one part of the glue with one part water. Apply the mixture to the cardboard surface and let it dry for two hours. You can touch to check if it’s dry.
After a few hours, apply a second coat of the PVA glue mixture. Get the solution to the underside and inside of the box then let it dry for two hours.
For a third coat, prepare a new mixture with two parts PVA and one part water. This is a more concentrated glue mixture. Again apply the mixture and let it dry for a couple of hours. By this time you should notice a shiny appearance on the cardboard surface.
Repeat the same process once again and this time give attention to the edges, corners and the inside of the cardboard box.

Using Fiberglass Resin Coat

Many fiberglass resin coats are waterproof and are compatible with other gels and coat application. Moreover, not just on cardboard, it can be applied to almost anything from wood to metal, plastics and everything in between.

Prep the work area by spreading out sheets of plastic and newspaper on the floor. Pick a space with good ventilation. Then lay a sheet of silicone mat on which the cardboard box would sit. The resin will harden after application and it is less likely to stick to the silicone mat. Next, don’t forget to put on proper safety gear such as rubber gloves and goggles.
Mix the polyester resin with the catalyst; because it sets in about 15 minutes, it is preferable to start with a small batch and mix up later. Mix 12 drops of catalyst per ounce of the resin.
Use a brush to apply the resin mixture onto the cardboard surface. In the first batch, finish off layering the outer surface of the cardboard box. Apply enough resin that it fully penetrates the cardboard box.
Allow the resin coat to dry for about 24 hours before applying the second batch of the resin. If you have covered all of the cardboard boxes, you can apply a second coat both the bottom and the outside layer of the box. Let it dry for 24 hours before using the box.

Using Shellac Solution

Shellac is produced from lac bugs and is used as a lacquer for musical instruments. You can brush the Shellac solution onto the cardboard box or directly bathe the box in it.

Prep the workstation by spreading sheets of plastic or old newspaper on the floor. Next, prep the Shellac solution.
Mix 5 ounces of Shellac with 1 ounce of Borax. Take a pot of water and bring it to boil. Add the mixture and keep stirring until the solution is even.
Use a mesh to drain the solution into a separate container. If you don’t have a fine sieve, you can use cheesecloth or muslin.
Now apply the Shellac solution directly on the cardboard box or bathe it in the solution, then drain it out by hanging it on a wire.

Using Lacquer

Applying Lacquer is probably the easiest way to waterproof your cardboard box. Get a few cans of Lacquer and you are good to go!

Prep the workstation by spreading plastic sheets or old newspapers on the floor. Pick a well-ventilated space because it is a spray on application.
Get a can of Lacquer and spray on the outer surface of the cardboard box. Let it dry for a few hours and then apply the second layer of lacquer on the inner side of the box, then let it dry for a few hours.
During application, the cardboard box itself may seem moist, but after drying you will notice a thin layer of protective coating on the cardboard box.

Using Alum Mixture

Alum is a rather homemade solution which can waterproof your cardboard box. You can use a spray gun to apply the final solution or use a brush to apply the alum mixture.

Prep the work area by spreading plastic sheets or old newspapers on the floor. Place your cardboard box on the floor.
Get a pot of water and heat it gets it a little warm for the mixture to dissolve. Pour 8 ounces of alum, 3 ounces of grated castile soap, 4 ounces of natural glue and stir the solution until it is even. Note that the water should not boil and the stirring process can take up several minutes.
Pour your solution to a separate container. Now use a brush or spray gun to paint a layer of alum solution on the box. Spray both the inside and outside of the box and don’t use too much solution on the box; use only a thin layer.

Using Paraffin Wax

Laying paraffin wax on cardboard box has been the most common process of waterproofing. However, it is not as efficient as other spray-on solutions.

Prep the workstation by spreading out plastic sheets and lay over the old newspaper on the floor, on which the cardboard box will sit.
Pour a few inches of water on the bottom pot of a double boiler pot.
Put 8 ounces of paraffin wax on the top pot.
Set the double boiler pot on low heat and stir the wax continuously until it melts completely.
Use a paintbrush or sponge brush to apply a thin layer of wax on the inside an outer surface of the cardboard box, then let it dry for a few minutes.
After the first layer has dried, apply a second thin coat of melted paraffin wax, then let it dry for a few minutes before using the box.

Using Self-Laminating Sheets

The self-laminating sheet is an inexpensive DIY method to waterproof your cardboard box. However, you have to buy several self-laminating sheets to cover all sides of the box.

Buy five self-laminating sheets, on for each side of the box and one for the bottom. Measure your cardboard box beforehand to get the right size sheets.
Use sheets to laminate one side at-a-time. Place the first side between two sheets of the laminating plastic. Keep the sheet with adhesive backing in the inside of the box.
Lay the box sideways on the floor, resize the laminating sheets and press down using a weight such as books, water bottles or with your hand. Keep the sheets pressed for a few seconds for them laminate.
Repeat the process for all sides to laminate the whole box. If you want you can also laminate the flaps and for convenience, you can open the bottom side while pressing down the laminating sheets.

Using Rubberized Coating

The rubberized coating can be another great way to give a complete waterproofing layer on the cardboard box.

Pick a workplace with good ventilation as the fumes can be toxic. Place drop cloths or plastic sheets or old newspaper on the floor. Place the cardboard box on top of the prepped floor.
Use a small paintbrush or roller to apply the rubberized coating over the cardboard box. The best about the coating is it covers all parts of the box including the edges and corners.
Leave the coating to dry for a few hours before using. The coating itself must come with a set of instructions, which you should follow as it may vary depending on the manufacturer.

Along with the aforementioned ways, you could also use a more sophisticated hydrophobic coating such as Rust-Oleum NeverWet. This is an extremely hydrophobic coating that can be sprayed on practically anything, even fabric; it will not let even a drop of water to stick to the surface.

Benefits of Waterproofing Cardboard Box

Your contents are safe from outer elements even in harsh weather condition
Some waterproofing coatings also strengthen the cardboard box, making it preserve its strength and shape even if handled harshly by package handlers.
Reuse cardboard boxes multiple times
Use cardboard boxes to store items at home without the danger of moisture damage
Use cardboard boxes for craft
Protect your cardboard boxes and its contents from snow and dust as well

Waterproofing Cardboard Boxes Tradeoffs

Most waterproofing coating makes the cardboard box un-recyclable
Coatings prevent any further printing on the box
Some coatings don’t last long and need to be applied multiple times in the future
Waterproofing coating is brittle and may break under pressure
You cannot store food items in a waterproof treated cardboard box

Conclusion:

The waterproofing cardboard box is a good idea if the weather is bad or you are transporting a valuable item. Plus, it helps to preserve its structure and can be reused several times. Some coatings also work as a pest repellant, which works great if you are planning to stack your cardboard box in the basement with your old books. On the other hand, a cardboard box is inexpensive and sometimes available for free. These boxes are meant to be recycled instead of being repurposed for your personal projects. Paints, coats, resins, etc. makes the box unrecyclable. So, after you are done with the cardboard box, you can let it be recycled, it will be thrown out like other waste products. That said, waterproof is an art in itself, which needs some experience. If you are new, don’t get mad if you couldn’t get it right the first time; after all, you are dealing will delicate paper product. Next time you decide to create a cardboard pet house or a cardboard boat, you know how to waterproof it.

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