Most of us live in PLA, PETG, and the occasional spool of ASA when a part needs to survive a hot car. Zack Freedman of Voidstar Lab spends his time at the opposite end of the catalog. For the latest entry in his long-running Every Filament series — titled “Printable iron? Rubber filament?! The most exotic printable polymers!” — he rounds up the strangest materials he can feed through a desktop machine, including an iron-filled compound and a genuinely flexible, rubber-like filament, to sort the usable from the merely weird.
What the video covers
The premise is the same one that has carried the whole Every Filament run: take polymers that rarely leave the spec sheet and find out whether they earn a place on a real desktop printer or just drain your wallet. Per the video’s own framing, this installment leans into the exotic end — a printable iron-filled material and a flexible, rubber-like filament headline the lineup of “most exotic printable polymers.” Freedman’s recurring angle is to report how each one actually behaves at the nozzle rather than restating the manufacturer’s pitch.
That kind of hands-on materials testing is hard to find written down anywhere reliable. A spec sheet will tell you a filament’s nominal print temperature and a marketing tagline; it won’t tell you how brittle it is on the spool, how badly it grinds a brass nozzle, or whether the finished part lives up to the name on the label. A maker methodically working through the oddball catalog is genuinely useful reference — and worth treating as one person’s results on one set of machines, not a universal verdict.
The bigger picture: what “exotic” filament actually means
The materials Freedman is poking at aren’t science fiction — they’re established but niche categories that most hobbyists never touch:
- Metal-filled filaments (iron, copper, bronze, steel) are a PLA or PLA-style base loaded with fine metal powder. They print on a normal machine but are heavier, can be polished or even rusted for an aged-metal look, and the abrasive powder chews through standard brass nozzles — a hardened steel or similar nozzle is effectively mandatory.
- Flexible filaments (TPU and softer TPE/rubber-like blends) are sold by Shore hardness. Softer grades behave more like rubber but are notoriously hard to feed, especially through a Bowden setup, and reward slow speeds and a direct-drive extruder.
- Other “exotic” entries across the series have included wood-, carbon-, and glass-filled composites, conductive and glow-in-the-dark blends, and water-soluble supports — each trading some printability for a special property.
The throughline is that almost every exotic filament is a trade: you gain a look, a feel, or a material property, and you pay for it in print difficulty, hardware wear, or cost. A roundup like this is most valuable as a filter for which of those trades are actually worth making.
What to watch for
- Nozzle wear. Anything metal-, carbon-, or glass-filled is abrasive. If you’re going to chase these materials, budget for a hardened nozzle before the brass one wears out mid-print.
- Claims vs. results. Treat manufacturer numbers — “rubber-like,” “real metal,” strength figures — as the maker’s claims, and watch how the filament behaves in the video rather than how it’s marketed.
- Sponsorship context. This episode carries a sponsor (a nozzle maker), and the follow-up below is sponsored by a filament brand. That doesn’t invalidate the testing, but it’s worth knowing which segments are paid.
- Your machine, not his. Soft flexibles and abrasive composites expose extruder and hot-end limits. Results on Freedman’s setup are a starting point, not a guarantee for yours.
More from Zack Freedman
If the exotic-materials angle hooks you, his “Five Bizarre 3D-Printing Mysteries with Insane Solutions” is a natural follow-up — a problem-solving video that digs into strange failures and the fixes for them:
Credit: All footage and testing by Zack Freedman / Voidstar Lab. Any material properties or performance figures mentioned are the manufacturers’ claims as relayed in the video, not independently verified results. We summarize and embed creators’ work to point you to the original — watch the full videos and subscribe on Zack Freedman’s YouTube channel.
