Many 3D printing filaments are highly sensitive to moisture, and hydrated filament can ruin your prints. This guide covers the basics of drying and storing hygroscopic filament to ensure that you get the best print quality every time.

What is hygroscopic filament?

All 3D printing filaments used for FDM are hygroscopic, meaning that they filaments are prone to absorbing moisture from their environment. This moisture can cause significant problems for your 3D printing filaments.

Here’s a quick primer on filament: the thermoplastic material we use for 3D printing is a polymer material, which is a material comprising chains of molecules that are strung together to form a semi-rigid structure. When these polymer-based materials absorb moisture from the air, water molecules disrupt these chains, causing significant damage to the plastic structure and negatively impacting heating and extrusion.

While this sounds like a disaster, it isn’t difficult to fix if it happens to you. This article will cover how to identify whether your filament has been impacted by moisture and how to dry it out as well as some basic storage tips.

How to Store and Dry Hygroscopic Filament

Is my 3D printing filament wet?

Different 3D printing filaments absorb moisture at different rates, but it is fairly easy to identify a spool that has been damaged by moisture:
  • Uneven extrusion after calibration
  • Popping/cracking sounds when printing
  • Significantly decreased print strength and stability
  • Severe stringing after calibration
  • Notably textured prints

If you observe these problems after checking for basic calibration, leveling, and setting tuning, it’s likely that you are dealing with moist filament.

These are much more likely to occur with very hygroscopic print materials including PETG, nylon, PVA, and flexible filaments, as only a day out of storage or in a moist environment can ruin an entire spool. Drying should be performed as soon as possible to avoid further damage to your material.

Drying filament

Option 1: Invest in a filament dryer

As 3D printing becomes an increasingly common industrial and hobby practice, there have been numerous devices placed on the market that are specifically designed for managing common 3D printing problems like filament hydration. If you want to have a dedicated tool for keeping your filament in top condition, it may be worth spending a nice chunk of money on a desktop dryer like the Dynamism PrintDry.

There are many available filament dryers that employ different drying methods, but most are simple with a small footprint, allowing it to be stored next to your printer.
While the price tag may be a bit high for a machine dedicated to such a unique application, these machines offer the most reliable and specially tuned drying experience, which allows users to ensure that they don’t overdry their filament and keep them in perfect shape.

Option 2: Oven drying

A very easy and inexpensive method for drying filament is using a conventional oven. Note that this can only be used if your oven goes sufficiently low as you will have to set the oven temperature to just below the glass transition temperature of the plastic.

We’ve listed some basic temperature ranges below, but it’s important to look up manufacturer’s recommendations and community posts about people who have worked with different filament types as there are individual variations you may find, particularly with older ovens. After finding the right temperature, leave your filament in the oven for 4–6 hours to allow all the moisture to evaporate.

  • PLA: 40–45 °C
  • ABS: 80 °C
  • Nylon: 80 °C
💡 Wait until your oven reaches the target temperature before putting your spool inside. Ovens will exceed the target temperature when heating up, and this can melt your plastic if placed inside too early.

Option 3: Make or use a food dehydrator

Food dehydrators are also relatively inexpensive yet effective tools for drying out moist filament and can be particularly helpful if you cannot guarantee that your oven can get sufficiently low for the filament drying temperature. Dehydrators are meant to function at lower temperatures, making them perfect for the careful drying needed when working with thermoplastics, and effective dehydrators can even be DIYed, cutting the cost significantly.

How to Store and Dry Hygroscopic Filament

Storing filament

To avoid having to take any of the steps listed above (or having to perform these steps again), it is crucial that your dry filament is stored properly.

Humidity-controlled environments are recommended for 3D printing filament storage. Some makers use an airtight box with desiccant packs, while others use carefully designed commercial solutions that are specifically engineered for use with filament.
Typically, using airtight bags and/or boxes will be enough, but if you have a lot of filament or work with particularly delicate materials, you may want to invest in something a little more robust.