Tips and Tricks: How to Store Filament

Have you ever noticed that your 3D printing filament makes cracking or popping noises as it comes out of the extruder tip, or that steam sometimes comes out as your model is printing? Or maybe your prints are all coming out odd and inconsistent even though you swear you’re printing with the exact same parameters every time. Well, that might be because you have a spool of filament on your hands that’s already reached its moisture saturation point. This is very common for 3D printing filament made out of hygroscopic plastics, which are plastics that will actually absorb the water content from the air. So if you live in particularly humid areas, this is definitely something to be aware of.

For reference, here is a list of hygroscopic vs. non-hygroscopic resins (from Plastics News)

Why is this a problem?

When your filament absorbs the water vapors from the air, the water can actually break apart the polymer chains that make up the plastic, a process called hydrolysis, and this can actually permanently damage your filament. During the printing process, the heat from the print head will cause the trapped water vapor to become steam and those gases escaping from the tip can interrupt the flow of the material, potentially creating a super soaker of molten plastic. Were the print to complete without flow issues, the water damage can also present itself in the finished product from general weakness to unexpected surface finishes.

So the results of using 3D printing filament that’s been affected by moisture can range from slightly annoying to somewhat catastrophic. But have no fear, there are ways to avoid this!

What’s our solution?

First and foremost, you’ll need to take stock of the type of filament you’re using, since some resins are hygroscopic while others are not. PLA and ABS, for instance, are hygroscopic so are definitely more susceptible to hydrolysis. HIPS, on the other hand, is not hygroscopic and therefore unlikely to be affected by ambient moisture. Depending on the type of climate you live in, choosing your standard printing material based on this property may save you a lot of headaches, but for those who live in dryer climates, this may be less of a concern.

But let’s say you’re a PLA-for-lifer and you’re concerned about hydrolysis, what can you do?

Filament Usage

Use it right away!

As soon as you open your roll of filament the material will be exposed to the open air. Leaving your spool hanging on your printer for days, weeks, or months, gives ample opportunity for water molecules to sneak into the plastic. If you’re using it regularly, you have a lot less to worry about.

3D printer using CLP U-HIPS filament while printing

Print in a dryer area

The room in which you do your 3D printing could have an effect as well. Again, based on your climate, this could be more or less of a concern. Consider finding a dryer area in your home and workplace to print if you want to minimize water absorption.

Filament Storage

If you can’t use all your filament at once, don’t worry. There are also ways to store your filament in order to protect it.

Vacuum sealing

Spool of U-HIPS filament in a vacuum sealer

If you have access to a vacuum packer at home (because don’t we all have one lying around?), place the entire spool in a vacuum seal safe bag, put in an activated desiccant packet, and seal it up. There’s a reason your filament likely is sent to you in a vacuum sealed bag, and part of it is to protect it from moisture! So this method will do the best job at keeping your filament as close to its original state as possible.

Sealable plastic bags
Spool of U-HIPS filament in a sealable plastic bag

For those who don’t have a vacuum sealer, you can also make a sealable plastic bag work! Similarly to vacuum sealing, you’ll put your filament in the bag, add in activated desiccant packets, and squeeze as much air out of the bag as you can before sealing it. Of course this won’t remove all the air so your filament will be exposed to some, but this method will definitely extend the shelf-life of your filament a great deal.

Airtight container

Spool of U-HIPS filament in an airtight container

An airtight container can do an equally good job as a sealable plastic bag and can store multiple rolls of filament at once depending on the size. If you use an airtight container to store your filament, make sure to add in either a large activated desiccant packet or multiple small packets.

Desiccant packets

If you’re wondering where you can get your own activated desiccant packets, almost every spool you receive should come with at least one. These are very easy to reactivate: all you have to do is microwave them for 30 seconds!

And remember, don’t leave your filament out for long periods of time, as that increases its exposure and potential for water damage.

We hope we’ve helped you uncover the mystery behind some of your failed prints and given you some helpful solutions! Happy printing!

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