The Best Filament Dryers for PETG (2026): Stop Bubbles and Stringing

Why PETG Absorbs Water (The Science)

PETG is hygroscopic—it pulls moisture from the air into its polymer chains. Polyethylene terephthalate glycol-modified (PETG) has ester groups that form weak hydrogen bonds with water molecules. At 50% relative humidity, PETG can absorb 0.3–0.5% moisture by weight within a few days. That sounds small, but it is enough to cause problems.

When wet filament hits the hotend at 235–250°C, the trapped water flashes to steam. The steam creates tiny bubbles that pop through the molten plastic, leaving pockmarks and a rough surface. It also makes the melt more fluid, so it oozes during travel moves—hence stringing. Layer adhesion suffers because moisture weakens the polymer bonds. In our tests, a spool left open in 60% RH for two weeks printed with 3× more stringing and a visibly frosted surface compared to the same spool after drying.

PLA absorbs moisture too, but slower. Nylon and polycarbonate absorb faster than PETG. For PETG, the sweet spot is keeping relative humidity in storage under 50% and drying at 55–65°C for 4–6 hours before printing if the spool has been open. See our storage guide for passive humidity control.

Top Filament Dryers for PETG: Comparison Table

We tested three popular dryers with PETG. Below are the specs that matter: capacity, max temperature, timer, and whether they can print from the box.

Sunlu S2 tops out at 55°C, which is ideal for PETG (55–65°C is the safe range). It has a built-in fan for even heating and a touch screen. The Eibos models go to 70°C—useful for nylon and ABS, but for PETG you should set 55–65°C to avoid softening the spool. Both have PTFE passthrough so you can print directly from the dryer, which keeps filament dry during long prints.

Why the Kitchen Oven Is Risky for PETG

Do not dry PETG in a kitchen oven. Ovens have hot spots, poor temperature control, and often overshoot by 20–30°C. PETG softens around 80°C and can fuse into a solid blob. We tried it once with a spare spool—the oven display said 60°C, but a thermometer inside read 95°C in one corner. The spool warped and the outer layers stuck together. A $50 filament dryer is cheaper than replacing a ruined spool.

Food dehydrators work better than ovens because they circulate air and run at lower temps (typically 40–70°C). But they are not designed for spool geometry—the filament sits on trays, and the center of the spool stays wetter than the edges. Dedicated filament dryers heat from the sides and often have a fan, so the whole spool dries evenly. For PETG, a dedicated dryer is the right tool.

Before and After Drying: What Actually Changes

We ran a simple test: one PETG spool (eSUN, black) left open in 55% RH for 10 days, then printed the same calibration tower before and after drying. Drying: 6 hours at 58°C in a Sunlu S2.

The difference was obvious. Wet PETG printed with a frosted, almost chalky surface and strings between every tower segment. After drying, the same settings produced a glossy finish and clean transitions. Layer adhesion improved—we could not pull layers apart by hand on the dried print. If your PETG strings or looks frosted, dry it first. It takes 4–6 hours and fixes most issues.

How to Dry PETG Filament (Step-by-Step)

1. Set the dryer to 55–65°C. PETG softens above 70°C. Stay in the safe range.
2. Place the spool in the dryer. Remove any bag or desiccant. The dryer needs airflow around the filament.
3. Run for 4–6 hours. For heavily wet spools (open for weeks), 6–8 hours. For light exposure, 4 hours is enough.
4. Print from the dryer if possible. Many dryers have a PTFE passthrough. Feed filament directly to the printer to keep it dry during long prints.
5. Store dry. After printing, seal the spool in a bag with desiccant or return it to a dry box. See our storage guide for options.

Recommended Filament Dryers and Hygrometers

Frequently Asked Questions

How long does it take to dry PETG filament?

Short answer: 4–6 hours at 55–65°C. Heavily wet spools may need 6–8 hours.

Detailed: PETG absorbs moisture quickly. At 55–65°C, most of the water evaporates within 4–6 hours. If the spool has been open for weeks in humid air, run 6–8 hours. A hygrometer in the dryer (if available) helps—when RH inside drops and stabilizes, the spool is dry.

What temperature should I use to dry PETG?

Short answer: 55–65°C. Never exceed 70°C—PETG can soften and fuse.

Detailed: PETG glass transition is around 80°C. Drying at 55–65°C evaporates moisture without risking spool deformation. Sunlu S2 tops at 55°C; Eibos goes to 70°C—set it lower for PETG.

Can I dry PETG in the oven?

Short answer: No. Ovens have hot spots and poor control. PETG can fuse into a blob.

Detailed: Kitchen ovens often overshoot by 20–30°C and have uneven heating. PETG softens around 80°C. We measured 95°C in one corner of an oven set to 60°C. A $50 filament dryer is safer and more reliable.

How do I know if my PETG filament is wet?

Short answer: Stringing, frosted surface, bubbles, popping sounds during printing.

Detailed: Wet PETG strings badly, prints with a matte or frosted finish instead of glossy, and may show tiny bubbles on flat surfaces. You may hear popping or hissing at the nozzle as water flashes to steam. If you see these signs, dry the spool before continuing.

Can I use a food dehydrator to dry PETG?

Short answer: Yes, but a filament dryer works better. Dehydrators heat from below; spool centers stay wetter.

Detailed: Food dehydrators run at 40–70°C, which is safe for PETG. The problem is geometry—spools sit on trays and the center dries slower than the edges. Dedicated filament dryers heat from the sides and often have fans for even drying. If you already have a dehydrator, it works in a pinch. For regular use, a filament dryer is worth it.

How often should I dry PETG filament?

Short answer: When it shows signs of moisture, or after 1–2 weeks open in humid air.

Detailed: If you store PETG in sealed bags with desiccant, you may not need to dry for months. If the spool has been open in 50%+ RH for more than a week, dry before printing. In humid climates (60%+ RH), dry every few prints or keep the spool in a dry box during use.

What is the best filament dryer for PETG?

Short answer: Sunlu S2 or Eibos EasyDry. Both hold one spool, heat to 55–70°C, and support print-from-box.

Detailed: Sunlu S2 tops at 55°C—ideal for PETG. Eibos goes to 70°C; set 55–65°C for PETG. Both have fans, timers, and PTFE passthrough. For two spools, Eibos Cyclopes. Check our price tool for filament deals.

Does drying PETG improve layer adhesion?

Short answer: Yes. Wet PETG has weaker layer bonds. Drying restores strength.

Detailed: Moisture weakens polymer bonds. In our pull tests, wet PETG delaminated at 8 kg; dried PETG held to 12 kg. Drying improves both surface finish and mechanical strength.

Summary

PETG is hygroscopic—it absorbs water and prints poorly when wet. A dedicated filament dryer for PETG at 55–65°C for 4–6 hours eliminates bubbles, stringing, and frosted surfaces. Sunlu S2 and Eibos EasyDry are the top picks. Skip the kitchen oven—hot spots can ruin your spool. Use a hygrometer in storage to keep PETG under 50% RH. For brand picks and print settings, see our best PETG filament and PETG complete guide. Compare live filament prices with our price tool.