Is My 3D Prin­ting Fila­ment Dry?

How to Detect Moisture in PLA, ABS, PA (Nylon) and More – And Why NIR Might Be the Future

If you’­ve ever strug­g­led with britt­le fila­ment, strin­gy prints, or unex­plai­ned sur­face issues, chan­ces are your 3D prin­ting fila­ment has absor­bed mois­tu­re. It’s one of the most over­loo­ked cau­ses of print fail­ure - and one of the har­dest to veri­fy quickly.

So how can you know if your fila­ment is dry? And could NIR (Near-Infrared) spec­tro­sco­py offer a bet­ter way to test it? Let’s dive into what’s curr­ent­ly pos­si­ble, what’s not, and whe­re the indus­try might be headed.

Why Filament Moisture Matters

Most popu­lar 3D fila­ments - like PLA, ABS, PETG, and espe­ci­al­ly PA (nylon) - are hygro­sco­pic. That means they absorb water from the air. Even small amounts of mois­tu­re can cause:

  • Steam bubbles and stringing
  • Wea­k­en­ed part strength
  • Poor lay­er adhesion
  • Incon­sis­tent extru­si­on and nozz­le jams

The effects are espe­ci­al­ly seve­re with nylon, TPU, and PC. But even “low-risk” mate­ri­als like PLA can suf­fer under the wrong conditions.

How Can You Tell if Filament Is Wet?

Reliable DIY methods:

  • Visu­al test: Watch for steam or pop­ping at the nozzle.
  • Weight check: Compa­re to known dry weight (if available).
  • Print test: Print a test cube and inspect sur­face quality.
  • Dry­ing + com­pa­ri­son: Dry the fila­ment, reprint, and compa­re results.

External resources:

What About NIR (Near-Infrared) Spectroscopy?

This is whe­re it gets interesting.

NIR spec­tro­sco­py can detect water con­tent in poly­mers - sci­en­ti­fic lite­ra­tu­re and indus­tri­al set­ups pro­ve it. The idea is simp­le: water absorbs spe­ci­fic NIR wave­lengths, and that shows up as chan­ges in the spec­tral fingerprint.

But here’s the catch…

While NIR is a powerful tool in lab and fac­to­ry set­tings, it’s curr­ent­ly not a cost-effec­ti­ve or relia­ble method for mea­su­ring fila­ment mois­tu­re in small-sca­le environments.

Here’s why:

  • Pre­cis­i­on: The mois­tu­re signal is subt­le and varies by polymer.
  • Cali­bra­ti­on: You’d need dif­fe­rent models for each mate­ri­al type.
  • Sur­face effects: Dust, colo­rants, and extru­si­on irre­gu­la­ri­ties can distort readings.
  • Cost: Lab-gra­de NIR sen­sors cost seve­ral thousand euros.

At Solid Scan­ner, we offer advan­ced NIR tools like the Ave­nir Pho­to­nics Sie­na spec­tro­me­ter - but they’re pri­ma­ri­ly used in recy­cling, R&D, and qua­li­ty con­trol, not fila­ment test­ing … yet.

What’s the Future of Filament Testing?

We belie­ve a more accu­ra­te, hand­held test for fila­ment dry­ness will even­tual­ly be pos­si­ble - may­be even based on NIR. We’­re wat­ching this space closely.

If you’­re a rese­ar­cher, fila­ment pro­du­cer, or 3D prin­ting inno­va­tor working on this chall­enge, let’s talk. We’re hap­py to explo­re pilot tests or partnerships.

What Can You Do Today?

Until afforda­ble sen­sors catch up, here’s your best approach:

  • Always store fila­ment in air­tight con­tai­ners with desiccants
  • Use a fila­ment dry­er or dehy­dra­tor (50 - 70°C for PLA, up to 80 - 100°C for nylon)
  • Weigh and docu­ment spools over time
  • Don’t trust “fresh out of the bag” - many spools are alre­a­dy par­ti­al­ly wet

Helpful products:

Bottom Line

Yes, fila­ment mois­tu­re is a real pro­blem. But no, the­re isn’t a fool­pro­of, afforda­ble sen­sor - yet.

We’­re not going to sell you a fal­se pro­mi­se. But we will keep explo­ring how advan­ced spec­tro­sco­py can sol­ve real pro­blems for real peo­p­le - whe­ther you’­re sort­ing pla­s­tics or pushing the limits of 3D printing.

Want to stay infor­med about NIR and mate­ri­als tech?
📩 Join our mai­ling list (see bot­tom of this page) for indus­try tips, use cases, and honest insights.

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