How To Keep Your 3D Printer Filament Dry (& What To Do If It's Not)

If you’re like me, you are very aware of your printer settings when you’re setting up a print job. You’re meticulous when it comes to the print temperature, bed temperature and print speed.

You make sure that all is right with your output program.

You try and use the highest quality printing filament. In short, you do everything you can to make sure that you end up with a printed object that is as close to perfect as possible.

Yet, despite all this careful preparation, you come back and find that your print has distorted, layers have stopped binding and instead of a perfect print, you’ve ended up with a mess. What the heck happened?

If this has happened to you, the likely culprit is water, specifically humidity infiltrating and breaking down your printing material. In this article, we’re going to take a look at why thermoplastics are susceptible to water damage and best practices for 3D filament storage. 

Hydroscopic Filament

We’ll also look at some best practices that you can use to keep your printing filaments as dry as possible. Finally, we’ll look at some of the ways you can detect water damaged filament before you print as well as techniques that you can use to try moist filament out so that you can safely use it again.

Why Water Damages Thermoplastics

All plastics are polymers or copolymers. Simply put, a polymer is a material that is made up of multiple long molecular chains of a single substance. For example, PVC or poly vinyl chloride consists of a bunch of vinyl chloride molecules.

A copolymer, on the other hand, is a material that is made up of several substances, each of which exists in long molecular chains. ABS is a copolymer and consists of strands of acrylonitrile, butadiene, and styrene molecules all bound together.

Polymers and copolymers are complex substances. They are designed to act in certain ways under specific conditions. For the most part, they fulfill this task admirably.

However, that task specific complexity comes with a price. What can be built up, can also be broken down and nothing breaks certain polymers or copolymers down quicker than water.

If you looked at a polymer or copolymer under a strong microscope, you’d see that the long molecular strands that make them up are woven and braded together, almost like rough cordage or rope. This means that there is plenty of space between and round these strands.

Because of this, most polymers and copolymers are hydroscopic. This means that as air circulates around and through these strands, the spaces between them pick up and hold the molecular water that is naturally present in the air.

Some filament materials, like Nylon can be extremely sensitive to water - where if they absorb just a little it can lead to problems when printing. 

Always Dry Nylon Filament

The more water vapor there is in the air, the more molecular water the copolymer can pick up or absorb.

These water molecules in the spaces between the strands not only increase the size of the material, they also tend to break down and alter the length of some of the molecular chains that comprise the polymer.

This process is caused hydrolysis. The result is an extruded copolymer plastic that doesn’t perform to design specifications.

How to Prevent Water from Damaging Your Thermoplastics

Even a small amount of absorbed water will negatively affect the end result of your print jobs. The best wat to avoid this problem is to prevent your print materials from coming into contact with water vapor in the first place.

Not keeping your filament dry

This is how not to keep your filaments dry. Luckily, after printing most thermoplastics are less sensitive to moisture absorption although this can still happen. 


The easiest way to do this is by storing you filament in an air tight container that contains desiccants.

When it comes to air tight, however, all containers are no created equally. When most people think of airtight, they think of plastic containers and bags. These are fine short-term solutions for the most part.

It’s better to store your materials in a plastic bag than leaving it unprotected in a drawer or box.

However, over time, plastic containers and bags are slightly water permeable. This means that the longer your printing materials sit in the plastic bag, the more water they are slowly absorbing.

You might be thinking how long does 3D printer filament last? 

Well, if you live in a humid climate, this process is accelerated. Eventually, even with the use of desiccants, you wind up with filament that is water damaged.

A better solution is to use Mylar bags, or bags made of a similar material, to store your thermoplastics. Mylar, as you know, has a metal layer that is embedded between two layers of plastic.

This metal layer keeps any water vapor that permeates the plastic layer away from your printing materials. The result is dry materials that are ready to give you great results every time you print.

Metallic Bag to Keep 3D Printing Filament Dry

Here at, this is the reason we provide metallic, sealable bags, along with desiccants, with every order we ship. It makes no sense to sell our customers the highest quality thermoplastics available and not give them the best means to protect those materials when they are not being used.

How You Can Tell That Your Printing Material Has Absorbed Water

There are two easy methods that you can use before you print in order to determine whether your material has absorbed water. First, you can measure the diameter of the material itself.

Remember, when a polymer absorbs water it begins to increase in size. The more water it absorbs the bigger the size increase will be. If the diameter of your filament has increased by 10% or more, it is likely that absorbed water is the cause.

The other way to determine if your filament has absorbed water is to extrude a small amount of filament prior to printing. We’ve probably all had the experience of sitting next to a fire and listening to it pops and crackles. This occurs because there’s water in the wood that is turning to steam as a result of the heat.

When you extrude thermoplastic that has absorbed water, the same phenomenon occurs. The heat of the print end causes the water in the plastic to expand. As the plastic extrudes, you will hear hissing or popping that is a result of the steam escaping. You may also see bubbling.

If you suspect that your filament has absorbed water you’re going to need to dry it out. In the next section, we’re going to show you how.


How to Dry Printing Material that Has Absorbed Water

If your filament has absorbed water, you’re going to have to dry it out before you can use it to print. The easiest way to do this is by using your oven to get the job done.

The first thing to do is check out the glass transition temperature for the filament that you are going to dry. You want to make sure that you keep your oven temperature below the transition temperature. In general, about 100C is just about right for a material like ABS.

For a harder material, like polycarbonate, 150C should do the trick. On the other hand, a material with a lower transition temperature, like PLA, doesn’t lend itself well to oven drying. This is largely because that lower temperature will cause it to deform even at your oven’s lowest setting.

Once the oven it up to temperature, place the spooled material inside and leave it there for four to six hours. If you have a convection oven, this drying time may be shortened since the circulated air removes more moisture from the material more quickly.

You can also 'recharge' the desiccant this way too, placing it in the oven over a low heat. 


Once the time is up, remove the material from the oven, allow it to cool and place it into a water impermeable container or bag along with desiccants. Make sure that the container or bag is completely sealed.

When you use any material that you have oven dried to print, be aware that it will slightly more brittle than normal. If you handle the material with care this should pose no problem, especially when you consider the superior results that you can achieve when using a properly dry print material.

If you've tried everything above, and that's still not help (and your filament is less than a few months old) we recommend getting in touch with your filament supplier and asking for a replacement. If they're worth their salt, they'll do this for you.

Well, we would anyway. 

Bags like the ones in the images above are delivered free with every order of, even the free samples. We hope you found this article useful - if you have any questions please don't hesitate to ask in the comments below. 

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