Many projects call for a waterproof adhesive solution, but it’s not always clear which glues are appropriate. In this article, I’ll explore the waterproof qualities of various different glues and adhesives, and explain the differences between them.
Is Glue Waterproof?
While many household glues provide some level of water resistance once dry, few are certified as completely waterproof. Some glues even break down completely in water, rendering them useless in humid or wet conditions.
In this article, I’m going to look at various different types of glue and find out what level of waterproofing each one offers. I will also explain the difference between water resistance and waterproof glue so you can decide what’s best for your project.
Waterproof vs Water resistant adhesives:
There are two different levels of protection an adhesive can have. For many household and DIY projects the distinction might not be too important, but for critical tasks involving water, it can mean the difference between success or failure.
Water resistant glue will hold up against occasional water contact, is fine to use in humid environments like kitchens and bathrooms, and you can use it outdoors.
The difference between water resistant glue and waterproof glue is that waterproof glue can be used in repairs that will be in constant contact with water, whereas water resistant glue should only be used for occasional contact.
In situations like pool repairs, leaky water pipes, water tanks, fixing a waterfeature or pond decoration, for use in aquariums etc – you need to use a fully waterproof glue because even glue marketed as “water resistant” may degrade when exposed to constant contact with water.
Which types of glues are waterproof?
Unfortunately, there are no hard and fast rules when it comes to waterproof glues. The only way to be 100% sure is to check the packaging, but there are a few rules of thumb.
- Most crafting glues like PVA School Glue and Fabric glue are not waterproof.
- Wood Glues, although PVA based are sometimes waterproof.
- Most water based adhesives are not waterproof.
- Any glues derived from animal products are usually not waterproof.
- Polyurethanes, Cyanoacrylates, Epoxies and Silicone based glues are usually water resistant, although some are waterproof too.
An adhesive that isn’t fully waterproof may still advertise itself as being Water Resistant.
Can I use a water resistant glue instead?
Although similar, there are a few differences between water resistant adhesives and fully waterproof adhesives, and it’s important to know what you need for your project.
Water resistant adhesives:
If an adhesive product is water resistant, it means that it can handle occassional contact with water, and is fine to use in a humid environment.
For example, you might use a water resistant wood glue if you were building a piece of wooden bathroom furniture, where the air is humid and the furniture may get a little wet sometimes.
Water resistant glue is not suitable for any critical situations where there will be constant contact with water or humidity.
Fully waterproof adhesives:
Fully waterproof glues and adhesives are suitable for projects where the glue needs to hold strong against constant contact with water.
Some situations you might need waterproof adhesive instead of only water resistant include patching a water tank, sealing round the kitchen sink, plumbing applications, use in fish tanks, or in marine applications.
In these situations, constant water contact may eventually lead a water-resistant adhesive to weaken and disintegrate over time, where a waterproof glue will hold fast.
How to tell if a glue is waterproof or water resistant?
The only way to really tell is by looking at the packaging.
Adhesives manufacturers are limited by the FTC in the US and in the relevant trading standards organizations across the world.
An adhesive must be able to hold up against continuous water exposure to advertise themselves as being “waterproof”.
Therefore, if you see some adhesives with “water resistant” on the packaging, you know it means they can withstand occasional exposure, or high humidity environments, but they are not suitable for critical projects involving constant contact with water, such as plumbing or marine use.
Some underwater projects require glue that can cure and stay strong while completely submerged.
There are specialist glues available which are completely waterproof and are designed for projects that may be submerged in water.
Which glue you need will depend on the material you’re working with.
There are glue variants for almost any material which are fully waterproof and will be able to hold underwater.
Does Glue work Underwater?
There are several glues which will maintain a strong bond, even when completely submerged for long periods. You can find out which glues are suitable for sustained contact with water by looking for “Waterproof” in the product packaging. (Not “water resistant”)
The glue you pick will depend on the material you’re working with.
There are wood glues, polyurethanes, CA glue, epoxy, construction adhesive, and waterproof putty all with completely waterproof versions available.
Can Glue Dry Underwater?
Although many glues are waterproof and do not deteriorate in water, this doesn’t mean that they will cure underwater if submerged before the glue has had a chance to dry.
Most adhesives work by suspending an adhesion molecule (the sticky part) in a solvent. When the glue is applied, the solvent evaporates, leaving the adhesive behind, forming a strong bond.
Therefore, submerging an adhesive while it’s still wet will stop the solvent from evaporating and therefore prevent the glue from being able to cure.
There are some specialist glues which are specifically designed to apply underwater, usually silicone based construction adhesives, adhesive pastes, and marine glue. Read the packaging carefully to make sure it’s not only waterproof but can cure underwater too.
What type of glue should I use in an aquarium?
For underwater corals or in-tank decorations, you can use a CA (superglue) adhesive. Make sure it’s fully cured before you put it in the water.
For the tank itself, you will likely want to use an acrylic cement for acrylic tanks, or a mechanical fastener with a silicone sealant for a glass tank.
If you’re building an acrylic tank – check out my other article on the best glue for acrylic here.
Underwater adhesive tape:
Most adhesive tape won’t work underwater long term, as eventually either the cloth or the adhesive (or both) will deteriorate.
This doesn’t mean they are totally useless though, just that they are not a permanent solution.
In a pinch, any duct tape will patch a small leak and hold for a while, even when submerged.
However, some duct tape is made from strong rubber instead of cloth. These tapes don’t have the tensile strength of regular cloth duct tape, but make up for it with superior adhesion power in water.
One example is Flex Tape, (made by the Flex Seal company) which is not only waterproof, but can even be applied while underwater. You might have seen some of the over the top ads demonstrating the tape on tv or youtube.
What type of glue is rain proof?
Any glue advertised as either “water resistant” or “waterproof” will be fine for occasional rain. There are water resistant variations of almost every type of glue, depending on the material you’re working with.
If you live in a very humid climate, you may wish to opt for a fully waterproof glue (as opposed to a water resistant glue), especially if your project is critical.
All weather glue for waterproof repairs:
Any water resistant glue will hold up well to occasional rain, but there are other weather conditions which can pose problems.
Weatherproof glue is usually waterproof, but can also withstand extreme temperatures and UV radiation.
What about glue for salt water?
Any waterproof glue will hold up equally well against seawater as it would against fresh water.
In seawater, the force of the waves is more likely to be a problem for your adhesive bond than the seawater itself.
Best type of glue for seawater?
The best glue for seawater fully depends on what materials you are planning to glue together.
There are waterproof variations of most types of glue, and any waterproof glue will hold up against seawater the same as it would against freshwater.
You may want to opt for a glue which is UV resistant also, if it’s going to be outdoors for long periods.
- Many glues are water resistant, but fewer glues are fully waterproof. You can tell the difference by looking at the packaging.
- Water resistant glues are fine for occasional exposure to water or humidity, but you need a waterproof glue for continuous exposure.
- Waterproof glues can be completely submerged once dry, but only a few specialist construction and marine adhesives can actually be applied while underwater.
- There are rubberized adhesive tapes like Flex Tape which can be applied underwater.
- Weatherproof glue needs to be water resistant, temperature resistant, and UV resistant.
- Waterproof glue works equally well in saltwater as it does in fresh water.
I hope this article was useful for you, and good luck with your project!
Thanks for reading