7 Methods For Waterproofing Cardboard Tested!

Due to cardboard surfaces becoming more and more popular for everything from arts and crafts to home decoration, we have noticed a bunch of questions being asked relating to waterproofing cardboard in the best possible way. Unfortunately, when it comes to actually waterproofing your cardboard surfaces successfully, there is an absolute ton of misinformation online with some people on social media recommending products that will not fully waterproof a cardboard surface time and time again.

As we have noticed a dramatic spike in the number of people reaching out about the various methods that you are able to waterproof cardboard recently as well as seeing so many recommendations of methods that really don’t work very well, we have decided to publish this article. Our hope is that by going over the more commonly recommended products for waterproofing cardboard in a dedicated article, we will be able to help our readers choose the method that is right for them as well as avoid methods that simply don’t work.

We have decided to feature the most common waterproofing recommendations that we see time and time again in this article to offer our opinion on how useful they actually are for waterproofing cardboard. We have added a table of contents below so you are able to skip directly to the sections of the article you need but we have tried to organise the article so the more effective products are at the top and then decline in their usefulness as the article goes on.

Can Cardboard Be Waterproofed?

Cardboard can easily be waterproofed by coating your cardboard in anyone of a wide range of popular sealing products. Although there are a wide range of products on the market that you are able to use to seal your cardboard and make it waterproof, we feel that a simple lacquer sealer spray is the best option for most people due to it being cheap, easy to use, and very effective.

As the majority of people who we see reaching out looking for tips and tricks to waterproof their cardboard are beginners to the arts and crafts space, the ease of use of a lacquer sealer spray really does score it points over the competition. Although there are different spray formulas on the market that do require slightly different methods of application for the sprays, the majority simply need to be held around six inches away from your cardboard when applied.

Once dry, the lacquer will form a protective, waterproof barrier over your cardboard protect it from any problems with water. Most of the more popular lacquer products on the market are available with a gloss or matte finish too allowing you to match up the finish of the lacquer with any paint that you may have used on your cardboard too.

How Can I Make My Cardboard Waterproof?

Most of the waterproof sealers that work with cardboard are very easy to apply. If you are using a sealer that needs to be applied via a brush then you simply apply it as you would a layer of paint. If you are using a spray sealer then you simply hold the canister around six inches away from the cardboard that you need to seal and then spray an even coat of sealer over the cardboard.

We would highly recommend that you always check the label of the specific sealer that you plan to use to waterproof your cardboard though. Different formulas may require a slightly different application method for optimal performance so always check the specific application instructions for your product.

In addition to this, some sealers may require two coats before they will be able to offer you full water protection with a single coat on your cardboard only offering basic water resistance. Depending on exactly what you need, simple water resistance may be able to get the job done but having your cardboard fully waterproof will be an important factor for some use cases.

Does Lacquer Sealer Spray Waterproof Cardboard?

Although a lacquer sealer spray is not as popular for waterproofing cardboard as some of the other common methods, it is probably the best option for most beginners to take. Most lacquer sealers will offer solid waterproof protection to your cardboard once dry with minimal issues during the application process due to being spray based.

Thankfully, even a decent lacquer sealer spray is very budget-friendly so the majority of our readers should be able to add one to their collection without having any problems with their budget. Please note the volume of the sealer spray that you order though as many of our readers will be fine with a very small amount of sealer if they are only needing to cover a small piece of cardboard. This can help keep your budget even lower by going with a small canister of sealant rather than the larger ones.

Due to many of the lacquer products on the market having very similar formulas, even the cheaper sprays can still offer decent protection to your cardboard from water. That said though, the better formulas are usually only around $5 more than the cheaper formulas but offer much better protection from water so we would highly recommend that you go with a better formula if possible for the added protection for your cardboard.

Do Varnish Sealers Waterproof Cardboard?

Varnish sealers can be an excellent option for waterproofing cardboard with most products being cheap and easy to use. Depending on exactly what you are doing though, the texture and look of a varnish sealer on your cardboard may cause potential issues as some of the popular varnish sprays are easily visible and can change the look of the card once applied and dry.

There are a ton of varnish sealer products online that all offer excellent protection due to them being so popular for arts and crafts and home decor. You are usually able to use varnish seals designed for arts and crafts or wood on cardboard without having any problems while still getting that tight, waterproof seal on the card once the varnish has fully dried.

Provided the change in the texture and look of your cardboard is not an issue, varnish can be a great way to protect your cardboard from water. If you are using the varnish sealers that come in a spray canister then the layer of varnish is often thin enough so there is only a slight difference in how the cardboard will look when the varnish is dry anyway so it can reduce the effects of this potential downside.

Does Flex Seal Waterproof Cardboard?

Flex Seal is an extremely versatile product and it can be a quick and cheap solution to make your cardboard waterproof with minimal skill or effort being required on your part. Although Flex Seal is easily able to make your cardboard waterproof, it will change the texture and look of it once the flex seal is dry.

Unlike the varnish spray products that we covered earlier in the article, Flex Seal, 14 oz, 2-Pack, Clear, Stop Leaks Instantly, Transparent Waterproof Rubber Spray On Sealant Coating, Perfect for Gutters, Wood, RV, Campers, Roof Repair, Skylights, Windows, and More results in a more obvious change to your cardboard rendering it useless for use in arts and crafts in many situations. That said though, for any out of side home decor use cases, Flex Seal can be an excellent option due to it being so robust and durable once dry while offering one of the best levels of waterproofing for cardboard in our list.

If you have outdoor surfaces that are supported by cardboard then Flex Seal is at the top of our list for adding a waterproof coating to it. Once the Flex Seal coat has dried, nothing is going to be able to get through and your cardboard surfaces outdoors will stand the test of time without issue for many years to come. One of the main problems with the other products on our list is that constant battering from wind or exposure to extreme heat or cold can cause their waterproof protection to fade where as Flex Seal will continue to protect your cardboard from the elements no matter what.

Does Polyurethane Waterproof Cardboard?

Water based polyurethane formulas tend to perform poorly when used to waterproof cardboard but solvent based polyurethane formulas can perform considerably better. That said though, even some of the solvent based polyurethane formulas on the market can end up having problems with creating a full waterproof seal on surfaces.

Depending on exactly what you need for your cardboard, polyurethane may be able to meet your needs but it really is not the best option out there for adding a waterproof coat to your cardboard. In some very specific situations, it may work but it is often better to think of a solvent based polyurethane product as something that offers water resistance protection at best, not waterproof protection.

As a general sealer, polyurethane really is an excellent option though it can offer great protection to many surface types with it being a common option for arts and crafts. It is only when water is added to the mix that its performance rapidly starts to drop off, especially if it is a water based polyurethane rather than a solvent based polyurethane.

Do Acrylic Sealers Waterproof Cardboard?

Although some people do recommend acrylic sealers as a way to add a waterproof coat to cardboard, they tend to underperform and offer no water protection at all. This is due to their water based formula and the actual sealer being able to rehydrate once water is added to it letting the water through it to the cardboad surface.

We would highly recommend that you avoid using an acrylic sealer on your cardboard if you are specifically looking for waterproof protection. Even small amounts of water are able to cause problems with many of the acrylic sealers on the market so they are not suitable for most peoples requirements when water is involved. We have seen some people report that they have used acrylic sealers in conjunction with other products to form a waterproof barrier for their cardboard or paper but this defeats the purpose of using the acrylic sealer, just use the other product by itself to form the waterproof layer.

To be clear, acrylic sealers are an excellent option for sealing your arts and crafts in pretty much every other situation and they are rightly an extremley popular product on the market right now due to their low price, great performance, and ease of use. The issue only really comes about when any type of water is added and even high levels of moisture in the air can cause problems with some of the cheaper acrylic sealer formulas on the market.

Does Mod Podge Waterproof Cardboard?

Although many people do use Mod Podge as a sealer for paper and card, it really does struggle once water is added in to the mix due to Mod Podge being a water based product. Even once dry, a small amount of water on Mod Podge can cause it to rehydrate and let the water through the layer of Mod Podge to get to your cardboard and ruin it.

Although Mod Podge is technically a PVA glue substitute, it does have a small amount of sealer in its formula. This is why, once dry, Mod Podge is able to offer some protection when used as a sealer provided there is no water involved. The low price of Mod Podge and its low price tag make it a very popular sealer within the arts and crafts community when you know that the art work that you seal with your Mod Podge will be kept in a nice and dry place.

Similar to using acrylic spray, we have seen some people say that they add other, fully waterproof sealers to their Mod Podge to then apply to their cardboard or paper to try and waterproof them. Although this could techncially work in some situations, we would highly recommend that you avoid doing this if possible and just use the other, fully waterproof sealer on your cardboard from the very start without adding it to the Mod Podge.

What Is The Best Way To Waterproof Cardboard?

The best way to waterproof a cardboard surface is to use a suitable lacquer sealer spray that offers waterproof protection once dry. Hold the cannister around six inches away from your cardboard surface and then spray a thin yet even coat of the lacquer sealer over the cardboard and leave it to dry. Some lacquer spray sealers do require a second coat to be applied so always check the lable of the paritcular product that you are using.

Although there are a number of methods that you are able to use to sucessfully waterproof your cardboard surfaces, we do think that a lacquer spray takes the top spot at the time of writing. They are very easy to use and too beginner friendly for any other the other products to take the top spot while also offering excellent protection from water with minimal overall effect on your cardboard.

If you are in the arts and crafts niche then you are able to use these lacqur sealer sprays on paper and other common surfaces to help seal them or form a waterproof barrier too. With most of the modern spray formulas having a price tag of less than $10, they are a real bargian and well worth adding to your collection with most sprays lasting you years depending on how often you use them.


That brings our article going over how you can go abour waterproofing cardboard at home with ease to an end. We have tried to go over all of the methods that we constantly see people recommending on social media as a way to add a waterproof coat to your cardboard as we often see products recommended that really are not fit for purpose.

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