Is PLA Water Resistant?  

Is PLA Water Resistant?  How to Make PLA Waterproof?

Is PLA Water Resistant?  How to Make PLA Waterproof?

PLA (Polylactic acid) is not water-resistant. The bioplastic material is derived from plants like rice, potato and corn.

That is the reason some people will compost PLA objects from failed projects.

If you left PLA printing material in an open place, it will take a few months to degrade into water, methane and carbon dioxide.

The older types of plastic, including disposable drink packaging, are made of impermeable waterproof materials.

The manufacturers derive the materials from petroleum and they can, therefore, last in the environment for 500-1000 years.

Because PLA breaks very fast, it indicates that it absorbs a lot of water from the environment to help with the decomposition process.

Moisture damaged PLA filament causes problems with three-dimensional printing. It can damage the 3D printer because it swells.

Feeding a swollen filament into your 3D printer will make it very hot and as a result, it will jam.

At times, a jam will end up in replacement of the hot end. Moreover, moisture trapped in the PLA filament can change into steam if the printer heats it rapidly.

The bubbles and tiny pockets of steam will interfere with the flow of the printing material passing through the hot end.

A material that absorbs more moisture will become weaker. If you stored a pure PLA material in water, the tensile strength will be reduced by around 6 percent.

If you dry it, it will lose around 33 percent of the tensile strength. That is noticeable.

When heating the PLA filament, it will lose water in the form of steam. So, any wet PLA will result in re-dried PLA which is around 33 percent weaker.

The same happens with PLA printed objects.

Some other factors that will influence the water absorption of 3D prints include the biological activities, light, temperature, filament brand, processing additives and some other environmental variables.

Water molecules diffuse between the polymer chains resulting in volumetric swelling. However, pure water will not affect the material.

Some elements in the soils will degrade PLA objects into small and small pieces until they get to the tetramers stage – 4 monomers.

At the size, microorganisms start eating the PLA leading to composting. So unless the chemicals are available in the environment you have placed your 3D object, it will remain intact. If it swells, you can dry it to take back to its original size.

How to Waterproof PLA Objects?

After printing a PLA 3D object for your aquarium, the next thing you will want to do is make it waterproof so that it can last for a long time. The same should happen when creating other items like dishes and mugs.

By making your prints waterproof, you will make it hard for the ink to dissolve in water. As an added benefit, you will make the objects more durable against mishandling and rubbing in addition to making them UV stable. You can shield the prints in several ways. Here is how to make the naturally waterproof and durable.

Method 1: Use wax

Wax is a good choice for people who want to make their 3D PLA prints waterproof. Wax is readily available and it will work like most other items sold in the stores. The coating is not only used in 3D printing – it is applicable in other industries too.

For example, producers of Carbide tools use Titanium aluminium nitride (TiAIN) to coat them as a way of preventing their wear when cutting. Socket heads and Allen wrenches are usually coated in black oxide to prevent wear and rusting.

And perhaps, you know that your bed is coated with either flame resistant resin. The use of coatings for 3D prints is for many reasons such as smoothing the edges, increasing the toughness and making them waterproof.

So, if you need to waterproof your PLA 3D prints for aquarium tank or outdoor use, coating is a good choice.

No 3D print is like the other. After all, you will print objects for different uses. So, you have to know where to coat and where to leave.

Apply wax to every part that will interact with water more often and if you do not know the part, wax the entire object.

Objects that will float on the water surface only need coating on their bottom and some little coating on the lower portions. Wax will prevent fluids from breaking into the object because it forms watertight barriers.

To coat the object, you will need:

  • Your 3D printed parts
  • Wax (you can try colours that will match the print)
  • Brush (for cleaning the object and to apply the wax)
  • A heat gun (to heat melt the wax)
  • Container (for heating the wax)
  • Razor or knife

Clean your object and melt the wax. When applying the wax, you will have to ensure that it is warm. After you are through with the application part, cool the object and remove any excess wax.

The excess wax will not be a problem but it will add unnecessary weight to the objects that should float.

Also, it will make them look odd, particularly if the application was uneven. You only need a very thin wax coat to make your 3D prints watertight.

Application of wax on objects will make them waxy, so you have to hold them tightly and use gloves to prevent them from slipping out of your hand or getting the hands waxy.

Heat guns can get extremely hot to use, so you have to be cautious when using them.

After applying the wax and allowing it to cool, you will have to check for any leaks. Fill your container with water and dip the object. Leave it for around 1 minute. If any water permeates, you will have to add more wax and try again until the object is watertight.

After your object is watertight, you will have to clean it. Take the razor or knife and remove excess wax carefully from the object.

Try to clean up the fingerprints you might have left. You can use any type of wax to make your objects waterproof and finding wax that matches the colour of your prints should be an important goal.

Method 2: Use fixative spray

Perhaps, use of fixative sprays is the most versatile alternative and one that will work for most PLA printed objects. To make the object waterproof, you just need to spray it directly. The spray will add a transparent layer.

Wait for the layer to dry so that you can use the print how you want and ensure that it is waterproof. The fixative spray will enhance the UV stability of your object. To keep the additional layer intact, the manufacturers of fixative sprays offer them in glossy, satin and matt finishes.

Can You Use PLA Printed Objects in Aquariums?

If you are planning to use PLA printed objects in your aquarium tank, you will have to choose the natural (or the white PLA). White PLA is clear and has a slightly yellow tinge. It does not contain any potentially toxic dyes that might harm your fish.

T-glass from Taulman is among the food-safe PLA filaments to try. It will not have any side effects in your fish. However, because PLA is biodegradable, you do not want it in your aquarium for a long time.

Will PLA Dissolve in Salt Water?

PLA will degrade faster in salt-water tanks. It will get brittle faster but it is unlikely to increase the nitrites in the tank. So, you should expect your PLA printed objects to last for a shorter time when in saltwater tanks.

Is PLA Drink Safe?

The bioplastic printing material Polylactic Acid (known as PLA), is made from natural materials like potatoes, tapioca and corn. So, it is common for many people to assume that it safe because it is made from the things we eat regularly.

That might not be the case. Even though it is safe to use for liquids and food, the hot ends of most 3D printers are likely to release many materials that are not safe.

First, the colourings used in the PLA filament contain additives that might not be safe if they get into contact with your drinks or food. Producers find it hard to use natural or virgin PLA without adding colours that would eliminate the risk.

Secondly, the PLA printed 3D objects contain holes and cracks that allow food to be stuck and the result is the growth of mould.

PLA might be safe for some simple things like single time use dish or water cup, but repetitive usage will lead to many health complications. The material is not a good choice for kitchenware.

But because 3-dimensional printing is evolving rapidly, there is a big possibility that shortly we might have plastic materials to facilitate the printing of kitchenware.

For now, using PLA to print your dishes and mugs is a bad idea.

Other Waterproof 3D Filaments

The most popular 3D filaments are Acrylonitrile Butadiene Styrene (ABS) and Polylactic Acid (PLA). However, there are other filaments like Polylvinyl Alcohol (PVA), PolyEthylene Terephthalate (PET) and High Impact Polystyrene (HIPS) filament.

If you need a waterproof filament for printing your aquarium tank objects, try PET and Nylon. PLA can cause fatal damages after it starts degrading.


PLA is biodegradable and the two primary things that make it break down are sunlight and moisture. So, water and light are the main enemies of PLA and they will dictate why you need the PLA objects.

If you are planning to use the objects in a moist environment or your aquarium tank, you will have to rely on other methods to waterproof them. Spray some polyurethane sealer or wax. You can opt for the waterproof filaments like Nylon and ABS.

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