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How to Waterproof Cardboard? 5 Simple Ways

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Cardboard is a cheap and reliable material that’s used for lots of applications, not just for shipping boxes. Some particularly popular ways to use cardboard involve arts and crafts and home decoration projects. One of the biggest weaknesses of cardboard is its susceptibility to moisture damage. It can get easily damaged by water and, in the case of cardboard boxes, the contents inside can also become affected. The best solution is to find a way to waterproof cardboard materials.




There are different approaches you could try if you’re interested in making cardboard less susceptible to water, even completely resistant to moisture. However, the basic principle stays the same: you can’t modify the material itself to waterproof it but you can add a waterproof coating to cardboard that resolves the problem. Various sealing products can be used to effectively create a protective barrier on the surface of cardboard and make it impervious to water damage.




Take a look at our helpful guide that will show you the best ways to properly waterproof cardboard.

1. Apply a Lacquer Sealer Spray

Lacquer Sealer Spray




While there are more advanced waterproofing methods out there for cardboard, lacquer sealer spray is among the best to consider as a beginner. This type of spray is reasonably affordable and easy to apply to cardboard surfaces. It creates a solid waterproof coating that becomes dependable once the spray has fully dried. Before using lacquer sealer sprays, remember to ventilate the space properly because these coatings are typically flammable.




Keep in mind that not all lacquer sealer sprays provide the best waterproofing performance. It’s recommended to get one with a quality formulation for ideal results. Check out this lacquer sealer spray model. Make sure you purchase the right quantity as well to match the needs of your project. Larger surfaces that need to be waterproofed will usually require more than a small spray can.

2. Use Flex Seal

Flex Seal




If you’re mainly looking to waterproof cardboard boxes, Flex Seal is an excellent product to try. This is a rubber sealant coating that’s easy to use and very cost-effective considering the way it can extend the lifespan of cardboard exposed to moisture. Flex Seal is a more durable option if you have cardboard surfaces outdoors that require protection from the elements.




After it gets dried, the sealant will ensure that moisture can’t penetrate the thickly formed layer. While this sounds great for many practical cardboard surfaces, you might need to avoid Flex Seal coatings if you work on arts and crafts projects. This is because the coating will clearly change the texture of cardboard and make it mostly unusable for creative applications. As opposed to other waterproofing methods out there, the protective layer shouldn’t fade away too easily. You can apply Flex Seal properly once and then enjoy waterproof cardboard for years.



3. Try a Varnish Sealer

Varnish Sealer




Although it can modify the appearance of cardboard in some cases, varnish sealers are recommended for anyone who needs to waterproof cardboard. You simply need to pay attention when selecting products to choose a varnish sealer mainly designed for arts and crafts applications. These products offer great overall protection, particularly when it comes to strong resistance to moisture.




Varnish sealers are not very expensive and just as easy to use as other waterproofing options on this list. Take a look at our recommended varnish sealer to use for cardboard. If you’re worried about the problem of an altered cardboard texture, it’s a good idea to use a varnish sealer spray that applies a thin layer with limited visibility once dry. Check out this great option.

4. Consider Fiberglass Resin

Fiberglass Resin




Fiberglass resin is another type of coating that can be used to successfully waterproof cardboard. Some can even work efficiently together with other sealing layers to enhance the ability of cardboard surfaces to withstand moisture. Compared to other products, fiberglass resin is more versatile but it can also be a little more difficult to apply properly. The process can be a little messy and you need to be careful about the tendency of the resin to harden. Two coatings of this product could be necessary for complete waterproofing. Here’s an extremely strong fiberglass resin.

5. Go for PVA Adhesive Coating

Adhesive Coating




This is a strong adhesive coating but won’t truly create a waterproof cardboard surface. It’s good enough for most applications where solid water resistance is necessary. PVA glues have to be mixed with equal parts water to create a proper mixture for coating the cardboard boxes or other surfaces. A second layer of the adhesive should be added after the first one has dried to maximize water resistance. Take a look at this high-quality PVA adhesive.

By Stefan Bucur

Stefan is the founder and owner of Rhythm of the Home. He has 6 years of experience in home improvement, interior design, cleaning and organizing.

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