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Best Humidity for Storing 3D Printer Filament. Facts Explained

High relative humidity can damage most 3D printer filaments, and your prints may fail or turn out with several flaws. Wet 3D printer filaments can jam your hotend, extruder, or nozzle, and some may be in an unusable condition. So, what is the best humidity for storing 3D printer filament?

The best humidity for storing 3D printer filament is <30%. The maximum relative humidity for most 3D printer filaments is 50%, but such exposure shouldn’t be prolonged. The only 3D printer filaments you can store in humid conditions are the non-hygroscopic variants.

You’re probably aware of more than a dozen types of 3D printer filaments. These filaments don’t all have the same vulnerability or resistance to humidity and moisture. In this post, I explain the facts about the best humidity for all the popular 3D printer filaments and a few unique thermoplastics.

The Best Humidity for Storing Different 3D Printer Filaments

Every thermoplastic has unique characteristics. I’m not talking only about different filaments, such as PLA, ABS, etc. The same type of filament manufactured by other companies may not be equally hygroscopic. Thus, the best humidity, or its range for each grade, is likely to vary.

Additionally, some companies manufacture blends and special filaments. So, let me first share the best humidity ranges for 3D printer filaments, after which I shall address the caveats.

Here are the best humidity ranges for storing different 3D printer filaments:

Best Humidity for Storage3D Printer Filaments
0% to 20%Nylon (PA), ASA, PETG, PVA, and TPU
20% to 40%PLA, ABS, PE, PS, and CPE
40% to 60%PP, PC, PVC, PTFE, and HIPS
Disclaimer: The 3D printer filaments listed in the table are of standard or generic quality. This list excludes special filaments, such as the non-hygroscopic variants and blends. Also, the ranges are for storage containers and conditions, not the ambient relative humidity in a room.

Hygroscopic vs. Non-Hygroscopic 3D Printer Filaments

Filaments are thermoplastics. They are also polymers, which means the filaments are a chain of monomers. The polymerization process that creates polymers with monomers is not irreversible, a fundamental reason for your 3D printer being able to melt the filaments.

Since the polymers forming the 3D printer filaments don’t have an invincible bond, their chains are vulnerable to damage, primarily due to chemicals, including water. The universal solvent in the form of moisture or humidity causes hydrolysis.

Hydrolysis changes the physical properties and chemical characteristics of 3D printer filaments. However, the damage caused depends on the type and composition of the monomers and polymers. As a result, 3D printer filaments are hygroscopic or non-hygroscopic.

While hygroscopic filaments are vulnerable to water, the extent to which the polymers endure moisture or humidity varies. The same principle applies to non-hygroscopic filaments, too. Not all non-hygroscopic 3D printer filaments are equally resistant to water or moisture.

Thus, the percentage of relative humidity and the duration of exposure determine water’s impact on the quality of any 3D printer filament.

Here are a few facts you must be familiar with about the most popular 3D printer filaments:

  • Polyamide (PA) or nylon is more hygroscopic than polylactide or polylactic acid (PLA). Hence, PLA can endure 30% to 40% humidity, while nylon may suffer significant damage at more than 20%.
  • PLA is less hygroscopic than acrylonitrile butadiene styrene (ABS). So, PLA may not undergo as much structural or characteristic change as ABS at 40% or 50% relative humidity.
  • Polypropylene (PP) and polycarbonate (PC) are hygroscopic but more chemically inert than PLA and ABS. Thus, PP and PC can endure slightly higher relative humidity than PLA.
  • High-impact polystyrene (HIPS) is non-hygroscopic to an extent. Therefore, HIPS 3D printer filaments can tolerate much higher relative humidity than PLA, PC, or PP.
  • Special non-hygroscopic 3D printer filaments are resistant to relative humidity. A blend or enhanced 3D printer filament tested and proven to be non-hygroscopic is not vulnerable to moisture, irrespective of the relative humidity in the atmosphere.

Companies like FILOALFA manufacture non-hygroscopic filaments, such as PP-CF and PP-GF. However, not all filaments of such companies have this attribute.

Also, non-hygroscopic doesn’t mean these 3D printer filaments won’t react to water. This characteristic is limited to relative humidity or moisture in the air.

The Best Ways To Protect 3D Printer Filament From Humidity

The easiest way to protect 3D printer filament from humidity is by storing a spool in an airtight container or can and keeping it in a relatively cool and dark place. Apart from humidity, most 3D printer filaments have an optimum temperature range for storage.

So, if you don’t plan to use a particular 3D printer filament for a while, pack it in a resealable container or airtight bag. Fetch the filament and get the spool out of the container only if you have to load it on your 3D printer. Don’t hang filament spools on hooks in the open.

3d printer filament sealed in plastic bags

Those living in humid regions may buy filament containers with a vacuum seal. Alternatively, you can use desiccants, such as silica gel. You’ll find desiccants in different forms, including packs, beads, etc. A few desiccants are rechargeable so that you can reuse them for a long time.

Some users have to worry about high humidity while working with 3D printer filaments, such as when it rains or during a rainy season. In such cases, using a dehumidifier is a practical solution. Otherwise, you may have to dry your 3D printer filaments before loading them.

Irrespective of all the preventive measures you can take, you may have a spool of filament partly damaged by humidity. Try to salvage such filament by heating or dehydrating it. You can dry 3D printer filaments by heating them in an oven below their glass transition temperatures.

Final Thoughts

Sustaining 10% to 20% humidity is a challenge in most places, whether you use desiccants or a filament container. So, aim for a more realistic ~30% for most 3D printer filaments, except nylon. The impact of +/-10% around 30% relative humidity is almost incognizable for PLA, ABS, etc.