Prusament PETG Ultraglow Green: The Brightest Glow-in-the-Dark Filament Just Launched

The Big Claim

Prusa Research launched Prusament PETG Ultraglow Green on February 19, 2026, and they are not being shy about it: they call it the brightest glow-in-the-dark filament on the market. Full stop. No caveats.

Bold claim — but they actually backed it up. Prusa ordered competing glow filaments, printed identical benchies from each, charged them all under a 405nm UV lamp for 20 minutes, and photographed the results. Ultraglow Green was noticeably brighter than everything else they tested.

So: does it live up to it? Based on what we know from the official specs and Prusa's own transparency about the trade-offs, the answer is mostly yes — with some important caveats about what it costs and what it demands from your printer.

Why PETG Instead of PLA?

Almost every glow-in-the-dark filament on the market uses PLA as the base polymer. PLA is easy to print, cheap, and beginner-friendly — but it is also weak under heat and not particularly tough.

Prusa chose PETG deliberately. PETG is stronger, handles higher temperatures, and is more moisture-resistant than PLA. That means Ultraglow Green is not just a novelty filament for glowing Halloween decorations — it is suitable for functional parts that need visibility in low light: emergency markers, safety handles, switches, tool components.

If you want to print a glow-in-the-dark endstop cover that actually lasts, or a cable guide you can find in a dark enclosure, PETG is the right base. This is a genuine differentiator.

The Science of the Glow

Older glow-in-the-dark materials used phosphorus compounds, which raised legitimate safety concerns. Modern alternatives use strontium aluminate, which is non-toxic, non-radioactive, and chemically stable — it does not react with water or common chemicals.

Strontium aluminate works by absorbing light energy (UV is most effective, but sunlight and strong LEDs work too) and then re-emitting it slowly. Prusa maxed out the concentration — as much strontium aluminate as physically possible while maintaining printability. The result: a weak but visible glow lasting 6-8 hours in total darkness after a 20-minute UV charge.

That is significantly longer than most cheap glow filaments, which fade to invisible within an hour.

Pricing and What You Get

Prusament PETG Ultraglow Green is available now from Prusa's eshop in two sizes:

• 800g NFC spool: $82.99 USD / €69.99 EUR
• 25g sample: Also available if you want to test before committing

That 800g price is roughly double what you would pay for standard Prusament PETG. It is expensive. But the strontium aluminate content is the reason — high-grade phosphorescent powder is not cheap, and Prusa packed in as much as the filament could physically hold.

The 25g sample is a smart option if you have never printed with abrasive filaments before and want to check your setup before buying a full spool.

Additional colours beyond green are described as coming soon.

What Your Printer Needs

This is where Prusa's transparency earns real respect. They are upfront that strontium aluminate is the most abrasive material they have ever put into a filament — harder than hardened steel nozzles. Here is what you need to know before loading a spool:

Hardened Nozzle: Non-Negotiable

A brass nozzle will be destroyed quickly. Prusa describes the effect as "liquid sandpaper" going through your hotend. You need a hardened steel nozzle at minimum. If you plan to print large quantities, they specifically recommend the E3D DiamondBack nozzle, which is harder than strontium aluminate and will not wear out from the filament alone.

Go 0.6mm, Not 0.4mm

Prusa strongly recommends a 0.6mm nozzle diameter. The abrasive particles can cause partial clogs in 0.4mm nozzles, especially standard (non-high-flow) variants. Prusa does provide 0.4mm profiles for those who need them, but 0.6mm is the safer choice.

Long-Term Wear

Even with hardened components, regular high-volume printing will cause wear — on PTFE tubes, hardened steel nozzles, and mechanical parts like Nextruder gears. Occasional printing is fine. Farm-level use will shorten component life.

Practical Applications

With PETG as the base and serious glow properties, here is where Ultraglow Green makes real sense:

• Safety and emergency markers — exit signs, emergency kit labels, anything that needs to be findable in a power cut
• Low-light functional parts — switch labels, cable markers, control panel indicators
• Multi-material accent printing — print functional parts in standard PETG and add glowing accents on an XL or other multi-material setup
• Toys, props, and decor — the obvious use, but now with much better glow and durability than PLA-based alternatives

Verdict

Prusament PETG Ultraglow Green is the real deal — at least on paper and from Prusa's own comparison testing. The brightness claim appears substantiated, the PETG base gives it practical utility beyond decoration, and Prusa's candid acknowledgement of the abrasiveness trade-offs is exactly the kind of transparency that builds trust.

The downsides are real too: it is expensive at $83 per spool, it demands hardened nozzles, and heavy use will wear components. If you just want to print a few glowing models occasionally, a cheap PLA glow filament from eSUN will cost a quarter of the price and be less fuss. But if you want the brightest glow, a functional PETG base, and a material you can actually trust the specs on — this is the one to get.

Available now at Prusa's eshop. The 25g sample is a sensible first step if you have never printed with abrasive filaments before.