Wood fill, metal fill, and glow-in-the-dark PLA each produce results no standard PLA can match. They also share a requirement: the particle content means specific nozzle and settings adjustments that standard PLA doesn’t need. This guide covers all three.
Metal fill and glow-in-the-dark PLA both require a hardened steel nozzle. The particles in these materials are abrasive enough to wear a standard brass nozzle within hours of printing. The nozzle orifice enlarges as the brass wears down, producing inconsistent line widths and a degraded surface finish that gets progressively worse through the print.
Hardened steel nozzles are widely available for all common hot end types. They cost more than brass but last significantly longer with abrasive materials. If you print metal fill or glow PLA with any regularity, a hardened steel nozzle pays for itself quickly.
Wood fill PLA is less aggressive on nozzles than metal or glow fill, but a 0.4mm or larger nozzle is still required. The wood particles can clog a 0.2mm or 0.25mm nozzle. Standard 0.4mm brass handles wood fill reasonably well, but a 0.5mm or 0.6mm nozzle gives more clearance and reduces partial clog risk.
Wood fill PLA has wood particles or wood flour suspended in the base PLA. The surface texture of a printed part has a slightly grainy, fibrous quality. That texture is what allows standard wood finishing techniques to work on it.
Print settings: Nozzle: 190-210°C. Wood fill runs cooler than standard PLA to reduce the risk of charring the organic particles. Going too hot produces a darker surface colour as the wood particles start to scorch — this can be used intentionally to create variation in the wood tone. Bed: 30-60°C. Layer height: 0.15-0.28mm. Fine layer heights with wood fill don’t improve surface quality and increase print time. 0.20mm is the practical standard.
Sanding: Start with 120-grit to remove layer lines and flatten the surface. Move to 220-grit to smooth. Finish at 320-400-grit for a surface ready for stain. Sand with the grain direction if the part’s geometry has a clear long axis — it produces a more convincing wood look.
Staining: Oil-based and water-based wood stains both work on wood fill PLA. Apply with a brush, let it sit for 2-3 minutes, then wipe off the excess. The wood particles in the PLA absorb the stain exactly as real wood does. Multiple thin coats build colour more evenly than one heavy coat. A final coat of matte varnish protects the surface and reduces the plastic look.
Partial clogging: if the nozzle clogs mid-print, increase temperature by 5-10°C and push through at slow speed. If the clog is persistent, cold pull at 90°C to extract the blockage. Regular cold pulls after wood fill sessions keep the nozzle clear for the next print.
Metal fill PLA has metal powder suspended in the base PLA. The weight is real — a copper fill print is noticeably heavier than the same object in standard PLA. Iron fill is heaviest. That weight is part of the effect on display pieces.
Common formulations: copper, bronze, brass, and iron are the most widely available. Each produces a different surface colour and polishing result. Copper gives a warm, reddish-brown tone. Bronze is more golden-brown. Iron is grey-black.
Print settings: Nozzle (hardened steel required): 200-220°C. Metal fill generally runs in the standard PLA temperature range. Bed: 30-60°C. Speed: 25-40mm/s. Slower speeds produce better surface quality and reduce the risk of partial clogs. Layer height: 0.15-0.28mm.
Polishing: The metallic effect after printing is present but muted. Polishing brings it out significantly. Sand progressively through 120, 220, 400, 800, and 1200-grit wet-dry paper, finishing with a metal polishing compound. The metal particles in the surface layer burnish under polishing and produce a convincing metallic sheen. The higher you go in grit, the more mirror-like the result.
Patina and aging effects: iron fill PLA can be treated with salt water or vinegar to develop surface rust, which is then sealed with matte varnish. The result looks like aged iron. Copper fill develops a green patina with ammonia fumes (same process as real copper). These effects take experimentation to control but produce results that look far more realistic than painted alternatives.
Glow-in-the-dark PLA contains phosphorescent particles that charge under light and release that energy as visible glow in the dark. The base colour of the filament is typically off-white or pale yellow-green in daylight. The glow colour is usually green, though blue and orange options exist depending on the brand.
Print settings: Nozzle (hardened steel required): 210-220°C. The phosphorescent particles are abrasive and require hardened steel. Layer height: minimum 0.15mm. The particle size limits how fine a layer height is practical before the particles cause inconsistency. Bed: 30-60°C.
Glow intensity and duration: The glow is strongest in the 20-30 minutes after light exposure and fades gradually over 4-6 hours to the faintest visible level. Brighter charging light produces a stronger initial glow and longer visible duration. Direct sunlight or a UV lamp charges faster than indoor ambient light.
Design considerations: The glow effect is most visible on surfaces with direct line-of-sight to the viewer. Recessed areas glow but are less visible than outer surfaces. Wall thickness affects how much of the outer surface glows — thinner walls allow more light through when charging, which can produce an interesting gradient effect if intentional.
Daylight appearance: Glow PLA in daylight looks pale and sometimes slightly translucent. It doesn’t look especially interesting unpowered. The visual payoff is entirely in the dark. Design pieces for glow PLA with the dark environment in mind, not the lit environment.
| Material | Nozzle | Bed | Layer Height | Nozzle Type | Key Notes |
| Wood Fill | 190-210°C | 30-60°C | 0.15-0.28mm | Brass 0.4mm+ | Sand and stain after printing |
| Copper Fill | 200-220°C | 30-60°C | 0.15-0.28mm | Hardened steel | Polish for metallic sheen |
| Iron Fill | 200-220°C | 30-60°C | 0.15-0.28mm | Hardened steel | Rust patina possible with salt water |
| Glow PLA | 210-220°C | 30-60°C | 0.15-0.28mm | Hardened steel | Charge under UV or direct sunlight |
eSUN produces wood fill, metal fill (copper, bronze, iron), and glow-in-the-dark PLA in their eSilk and specialty ranges. Their formulations run consistently within the settings documented here, which matters when you’re working through a finishing process that depends on predictable surface texture.
eSUN specialty PLA filaments are available through the eSUN Official Store.
Disclosure: the eSUN link above is an affiliate link. If you purchase through it, we earn a small commission at no cost to you. We only recommend products we use ourselves.
Specialty PLA variants use the same model files. Check each product page for material-specific settings notes.