Do you need to dry PETG?

By Asked 3D Content TeamPublished Last verified

Do you need to dry PETG?

Usually not from an intact vacuum bag: Polymaker pre-dries and seals every spool, and Bambu Lab rates drying PETG (glycol-modified polyethylene terephthalate) as recommended, not required. Dry it once an opened spool has sat out or starts popping. Bambu says to dry PETG Basic after 72 hours in air above 50 percent relative humidity (RH).

The number

Source Drying PETG before use A new, sealed spool Storage it asks for PETG water uptake
Bambu Lab drying wiki Recommended, not required, for PETG and PETG-CF; dry first if storage is uncertain Not addressed Below 20% RH, sealed with desiccant not given
Bambu Lab PETG Basic store page and data sheets “Dry out before use”; dry thoroughly after more than 72 h in air above 50% RH Once opened, dry before use Below 20% RH, sealed with desiccant 0.45% at saturation (25 °C, 55% RH); PETG HF 0.40%
Prusa Knowledge Base and Prusament PETG data sheet Gives a setting, but leaves PETG off its highly hygroscopic list (polyamide, polypropylene, PVA, BVOH) Not addressed Closed box with desiccant 0.07% in 24 h, 0.10% in 7 days (24 °C, 22% RH)
Polymaker wiki and PETG data sheet PETG is highly hygroscopic; drying is “crucial” Pre-dried, vacuum-sealed with desiccant, ready to print if the seal is intact A dry box while printing or storing 0.51% maximum (23 °C, 70% RH)
Flashforge PETG drying guide Hygroscopic, but less moisture-sensitive than nylon, PVA or BVOH Vacuum packaging “does not guarantee completely dry filament” 20% RH or lower with desiccant (HS PETG, PETG-CF) not given
Wang et al., BioResources, 2025 Drying improved every property they tested The dried roll settled back at its out-of-bag weight not tested 0.34 to 0.35% after 12 h at 30 °C, 90% RH

The Bambu Lab rows come from its Filament Drying Recommendations wiki, its PETG Basic store page and its PETG Basic and PETG HF data sheets. The Prusa row comes from its Knowledge Base drying article and the Prusament PETG data sheet. Polymaker’s row draws on its pre-drying and wet filament pages and its PETG data sheet, and Flashforge’s on its PETG drying guide. The last row is a peer-reviewed test on one transparent PETG. Each lab measured uptake under the conditions in parentheses, so compare the figures loosely. PVA is polyvinyl alcohol, BVOH butenediol vinyl alcohol copolymer, CF carbon fiber and HF high flow.

Why

PETG pulls water out of the air, and in the hot nozzle that water turns to steam. Polymaker says the pops or sizzling you hear are the vapor escaping. Bambu Lab blames the steam for bubbles, stringing, holes and weaker parts. In Wang et al.’s test, parts from the dried roll had 18.1 percent higher tensile strength and 48 percent lower surface roughness (Ra) than parts from the damp one.

The makers disagree on how sensitive PETG is. Polymaker groups it with nylon, PVA and TPU (thermoplastic polyurethane) as highly hygroscopic, meaning quick to absorb water. Flashforge calls it less sensitive than nylon, PVA or BVOH, and Prusa leaves it off its own list. Bambu Lab says its reformulated PETG Basic is less moisture-sensitive than typical PETG but still recommends drying it.

Humidity is where they agree. Polymaker says a humid home “greatly increases the risk,” and Flashforge says PETG takes on water faster in a warm, humid room than in a cool one.

Is PETG dry out of the box?

Usually, if the packaging held. Polymaker dries every spool with heat and airflow, then vacuum-seals it with a desiccant pack. It says that spool prints straight from the bag for most users if the vacuum hasn’t leaked.

Two PETG spools, one in a vacuum bag pulled tight around it with a desiccant pack, cut away, and one sitting loose in an opened bagA bag still tight against the spool with desiccant inside can go straight to the printer, while a loose or punctured one means unknown storage, so dry that spool first.2Vacuum bag pulled tight1Desiccant pack3Loose, opened bag
  1. Desiccant pack
  2. Vacuum bag pulled tight
  3. Loose, opened bag
A bag still tight against the spool with desiccant inside can go straight to the printer, while a loose or punctured one means unknown storage, so dry that spool first.

Wang et al.’s numbers fit that. Their test roll weighed 202.22 g fresh from its sealed bag. It took on water in the humidity chamber, then settled back at 202.22 g after 8 hours of drying at 70 °C.

Flashforge is warier: moisture can remain from production, get in through a bag that leaked in shipping, or outlast a saturated desiccant in long storage.

Should I dry new PETG filament?

Not by default. Print with it and watch. Flashforge says to dry a newly opened spool that pops, bubbles or extrudes unevenly before you touch the slicer, and that needing to doesn’t make the spool defective.

Dry it before the first print when the bag is no longer tight or you don’t know how the spool was stored. Do the same when the part has to look perfect: Bambu Lab recommends drying first for models “demanding high appearance and quality” whenever storage is uncertain.

When should you dry PETG?

  • It pops, hisses or bubbles at the nozzle. Flashforge calls this one of the clearest signs of wet PETG. Stringing alone doesn’t prove it: Flashforge says light strings with smooth extrusion point to temperature, travel or retraction.
  • It has sat open in room air. Bambu Lab puts typical indoor air at 45 to 65 percent RH, and its 72-hour line above 50 percent RH applies to PETG Basic. For filament in general, Bambu says a freshly dried spool at about 55 percent RH takes up enough water to hurt print quality within 2 to 12 hours.
  • It hasn’t been used in a long time. Polymaker says the safest move with a long-idle spool is to dry it first.
  • The room is humid or the print is long. Polymaker says highly hygroscopic filaments, PETG among them, often need to stay in a dryer while printing, especially in humid climates.

How to check it on your own print

  • Check the bag as you open it. If it’s tight against the spool with a desiccant pack inside, print. If it’s loose or punctured, treat the storage as unknown and dry first.
  • Check the spool’s heat rating. Bambu’s PETG spools are ABS (acrylonitrile butadiene styrene) rated to 70 °C, and Bambu warns that some third-party spools can deform during drying.
  • Dry it and reprint the same small file. Prusa sets 55 °C for 6 hours, Polymaker 60 °C for 6 hours and Bambu Lab 65 °C for 8 hours, in a filament dryer or forced-air oven. Never use a kitchen oven or microwave: Bambu Lab says their uneven heat can damage the spool or filament. Enclosed printers can also use the heated-bed drying settings. If the pops stop, moisture was the cause.
  • Put a hygrometer in your storage box. Bambu Lab asks for below 20 percent RH and Flashforge for no more than 20 percent. Bambu says filament stays dry for 2 to 7 days at that level. Flashforge says to let a dried spool cool before sealing it in a plastic bag.

Sources

  1. Filament Drying Recommendations, Bambu Lab Wiki (accessed October 17, 2026)
  2. PETG Basic, Bambu Lab Store (accessed October 17, 2026)
  3. Bambu Filament Technical Data Sheet V3.0, PETG Basic (accessed October 17, 2026)
  4. Bambu Filament Technical Data Sheet V1.0, PETG HF (accessed October 17, 2026)
  5. Drying filament, Prusa Knowledge Base (accessed October 17, 2026)
  6. Technical datasheet, Prusament PETG by Prusa Polymers (accessed October 17, 2026)
  7. We Dry our Filament Before Shipping, Polymaker Wiki (accessed October 17, 2026)
  8. Wet Filament, Polymaker Wiki (accessed October 17, 2026)
  9. Polymaker PETG Technical Data Sheet V3.0, Polymaker (accessed October 17, 2026)
  10. PETG Drying Temperature: How to Dry PETG Filament Properly, Flashforge (accessed October 17, 2026)
  11. Effect of drying treatment on the physical and mechanical properties of material extrusion-based 3D-printed PETG models, Wang et al., BioResources (2025) (accessed October 17, 2026)