Tip On How to Make Cardboard Waterproof?

September 16, 2025 Box Material

Cardboards serve many packaging and storage functions because they offer strong protection at affordable costs. However, the amount of damage from water exposure poses its most significant challenge to practical use. When cardboard comes in contact with water, it loses its strength. When the fiber is exposed to water, it absorbs, becomes soggy, and breaks apart. So, brands relying on cardboard to ship their products need waterproofing of this material for safety and durability.

So, let’s read this blog and learn how to protect cardboard from rain or moisture in general.

How To Make Cardboard Waterproof

Cardboard is made of wood pulp and tends to absorb water. Cardboard is an excellent and durable product packaging under dry conditions. Nonetheless, when it comes to humid environments, it merely withstands water. Some of the problems that you may have to face based on the exposure of cardboard to water are as follows:

Structural Weakness

Water interacting with cardboard fibers weakens the material and reduces its ability to withstand strain. Such cardboard can easily tear and cannot protect the packed items.

Bending And Warping

When exposed to water, cardboard loses its shape. This leads to bending and loss of structure. Persistent exposure to water leads to the disintegration of cardboard and makes it unsuitable for use.

Potential Mold Growth

Wet cardboard in humid air can develop mold and mildew, threatening personal health and creating strong odors. This further leads to damage to the packed items causing you a significant loss of products.

If you have to use custom boxes for shipping or outdoor uses, then their protection from moisture is crucial. The best thing is that there are several ways that you can protect your cardboard material from water so that you can use the boxes for moving goods or under unpredictable weather.

Waterproofing Cardboard Boxes

There are several methods that you can use to protect your cardboard material or boxes from moisture. From the use of coatings to the application of sprays and duct tapes, all can be used as an effective method to waterproof cardboard.

Using Waterproof Coatings

The use of coatings is one of the most effective ways to make cardboard waterproof. These coatings create a moisture resistance barrier and make sure that moisture does not deteriorate the quality of the boxes. There are several types of coatings that you can use based on your specific requirements.

Wax Coating

Wax coatings are one of the most common methods for waterproofing cardboard material. The application of wax coating creates a moisture-repellant barrier and keeps the cardboard dry. There are several ways of applying wax coatings, such as:

Paraffin Wax

Paraffin is the most common form of wax applied for waterproofing. It is melted and brushed onto the surface of the cardboard. After this, you have to weigh for the wax to dry and harden for the creation of a waterproof layer.

Beeswax

Beeswax works just like paraffin wax, but it is a sustainable option. So, brands looking for biodegradable coatings can opt for this. Apart from being sustainable, bees wax is softer than paraffin wax, due to which it keeps the cardboard flexible.

The best way is to melt the wax and dip the cardboard material in it. You can also use a brush to apply the coating and spread it evenly on the box surface. Make sure that the wax is set and hardened before using the cardboard to prevent improper application.

Plastic Coatings

Plastic coatings such as polyethylene and polypropylene are widely used to make the surfaces waterproof. These coatings are highly durable and resistant to water. The common application of plastic coatings is lamination.

Lamination

In this, a thin layer of plastic film is applied over the surface of the cardboard. This application is done mainly via heat and pressure. The laminated surface of cardboard becomes permeable to water and its strength as well as longevity increases.

There is one downside of the application of laminations, which is the cost of production. Another issue that brands have to face is the reduction in the recycling ability of cardboard. So it is better to use this option for heavy-duty applications or for sensitive products.

Acrylic or Latex Spray

Acrylic or latex can be used as a waterproof cardboard spray. These two are a great option and are designed to form a clear and waterproof barrier when applied on cardboard. You simply have to spray a thin, even coat of the product over the surface of the cardboard and let it dry.

Acrylic and latex both are available in two forms, the one is matte and the other is gloss. When you do not want to change the texture of cardboard but need a waterproof barrier then these two are ideal options.

Polyurethane Coating

Polyurethane varnishes are highly durable and waterproof coatings that can be applied to the cardboard to protect it from moisture. There are two types of polyurethane coatings, namely:

Oil-based Polyurethane

When you need to protect the cardboard material for long durations, then you can use oil-based polyurethane. It has only one flaw, which is that oil-based polyurethane takes longer to dry and has a strong odor.

Water-based Polyurethane

Water-based polyurethane is also one of the most durable water-resistant coatings. You can use it as an alternative to oil-based polyurethane when you need a sustainable coating with less odor on orders that need quicker turnaround time.

You simply have to brush polyurethane on the surface of the material and allow it to dry. If you need additional protection, then you can apply multiple coatings on the surface.

Waterproofing Cardboard with Tape

When it comes to the answer to the question “how to waterproof cardboard,” then one thing that comes to mind as a quick solution is the use of waterproof tape. This is an ideal option for edges and seams to prevent moisture from seeping into the cardboard box.

Gaffer Tape or Duct Tape

These tapes are made from strong and water-resistant materials and can be used to seal the seams or cover the surface of cardboard. You can simply apply the layer onto the surface of the material and press it to ensure that the duct tape has been sealed thoroughly.

Waterproof Packing Tape

Waterproof packing tape is specifically designed to be applied on custom boxes when they have to be shipped and stored. These tapes are made from vinyl material and have a strong adhesive backing that is made from vinyl or polypropylene.

How To Make Cardboard Waterproof With Oil-Based Solutions

Another technique involves using oil-based treatments to waterproof cardboard. These treatments can include mineral oils or linseed oil, which penetrate the fibers of the cardboard and create a water-resistant barrier.

Linseed Oil

Linseed oil is often used in arts and crafts projects that can saturate cardboard. When this oil is applied to the surface, it generally soaks into the material, and when it dries, it gives a natural, water-resistant surface. The application of oil may cause the cardboard to darken in color and impact the recyclability of the material. It is important to consider the trade-off when choosing this method. This means understanding whether the application oil is worth it at the cost of recyclability or not.

Using a Waterproofing Spray Or Sealant

You can use commercial waterproofing sprays or sealants to make your cardboard waterproof. These sprays are designed to protect porous materials such as cardboard, wood, or fabric from water. The spray forms an invisible barrier that repels water and prevents it from soaking into the cardboard.

You can find several types of waterproofing sprays that are formulated specifically for paper-based materials such as cardboard. Simply have to spray them over the surface of the material and allow it to dry. Some of the popular options are as follows:

Scotchgard Water Shield
Rust-Oleum NeverWet
Plasti Dip Waterproofing Spray

Additional Tips On How to Make Waterproof Cardboard?

When it comes to making the cardboard waterproof then there are certain things that you have to consider so that the cardboard material remains in safe and sound condition. Make sure you always see the following factors while making the cardboard waterproof:

Consider The Environment

If your cardboard boxes are exposed to extreme conditions such as rain or you have to store the boxes for a long term then consider using multiple layers of waterproofing. You can also use a combination of different methods to enhance the protection of the boxes.

Test First

To make sure that your selected method is good and useful, always test on a small sample. This also prevents damage due to adverse reactions such as discoloration or loss of flexibility of the material.

Use Multiple Coats for Maximum Protection

Another very important thing that you have to consider if you want to make your boxes long-lasting, is the application of multiple layers on the material. Specifically, if you are selling sprays or coatings then you must do this as they may wear off with time.

Storage Conditions Matter

Store the waterproof cardboard material under cool and dry conditions to avoid the premature breakdown of the protective layer. Direct sunlight and high temperatures can cause some waterproofing agents to degrade faster.

Wrap Up!

When it comes to the use of custom boxes then the damage due to moisture is the biggest hindrance one may have to face. To prevent this damage, it is vital to coat the materials with appropriate waterproofing agents such as coatings, varnishes, tapes, or oil-based solutions.