Humidity and Filament

[CrazyIvan]

I see on-line some people are almost paranoid about keeping their filament dry. I guess some types might by hygroscopic (water absorbing). So, questions:

1. Which filament is susceptible and which not?
2. What happens to a print if the filament is damp?
3. How big a problem is this, really?

[bryant]

1. Filaments like ABS, ASA, nylon and PETG are hygroscopic, meaning they absorb moisture from the air over time. PLA filament is much less susceptible to moisture absorption.
2. This makes the filament brittle and can cause poor layer adhesion, popping/cracking sounds during printing, and voids or weak spots in the finished print.
3. For moisture-sensitive materials, printing with wet filament usually leads to poor print quality. However, the effects can range from minor to completely failed prints depending on the moisture content.

[CrazyIvan]

Thanks for the reply, and I'm delighted to hear this does not affect PLA, but some follow up questions:

• What about TPU?
• Is this actually a problem in a normal domestic environment?

[bryant]

Thanks for the reply, and I'm delighted to hear this does not affect PLA, but some follow up questions:

• What about TPU?
• Is this actually a problem in a normal domestic environment?

1. TPU is somewhat hygroscopic, high humidity environments can cause TPU to absorb up to 2-3% water by weight, but TPU will give off the absorbed water and return to its original dry state when returned to lower humidity.
2. For specialized uses it may impact negatively. For most common domestic applications, the hygroscopic nature of TPU is not a major problem, it doesn't require any special considerations for products used in a normal home environment.