A mold line is the thin raised seam where the two halves of the mold met. On a 28 mm miniature it runs down the side of a leg, across a shoulder pad, through hair and along a sword edge. Primer does not hide it; paint makes it more visible, and a wash settles into it and draws a dark line exactly where you did not want one. Removing mold lines is the least glamorous step in the hobby and the one that separates a clean paint job from a "something looks off" one.
The good news: it takes three tools and ten minutes per model once you know the technique.
Tools used in this guide
- Miniatures & Wargaming collection — mold-line removal, basing, brushes and paints
- Hobby Knives, Blades & Saws
- Tapered Metal Files #150-#400 — 2-8 mm widths for corners and recesses
- #320-#5000 Sanding Sponges (Hobby Mio)
- Sanding Matchsticks — beveled abrasive tip for spots a stick cannot reach
- DSPIAE ES-A Electric Reciprocating Sander — for batches and resin
- Miniature Parts Pick-up Sticky Clay Pen · Rotating Painting Vise with Magnetic Base — for holding
Find them first
Hold the miniature under a desk lamp and turn it slowly. Mold lines show as a fine bright line catching the light; run a fingernail across suspect areas and you will feel them. Typical places: outside of legs and arms, sides of the head, edges of weapons, the rim of a base tab, and down the center of cloaks. Mark bad ones with a pencil if you are doing a squad.
The main technique: scrape, do not cut
Whatever the tool, the motion is the same: hold the blade upright, at 90 degrees to the surface, and drag it along the mold line with light pressure, in short strokes. You are shaving plastic, not slicing it. A blade held at a cutting angle digs in and takes detail with it; a blade held upright scrapes the seam flat. Do not scrape across the line: a perpendicular stroke chatters and leaves ripples.
- Scrape with the back of a hobby knife blade (the dull spine, or the edge held upright). Two or three light passes usually flatten the seam on hard plastic. Keep a fresh blade from the hobby knives collection; a dull blade tears soft plastic instead of shaving it.
- File tight spots. Where the seam runs into a corner (armpit, inside of a knee, between fingers), switch to a narrow file. The tapered metal files come in 2-8 mm widths and three grits (#150, #200, #400); the taper lets you reach into a recess without flattening the detail around it.
- Smooth. Finish with a fine sanding sponge (start around #600-#1000 for plastic, finer on smooth armor) so the scraped area has the same texture as its neighbors. For a groove or crease a sponge cannot enter, a sanding matchstick with its beveled abrasive tip gets in.
- Check again under the lamp, then wash the model in warm soapy water to remove dust and mold release before priming. Primer will show you anything you missed, so prime a test model before a whole army.
By material
Hard plastic (polystyrene kits, most modern wargame sprues). Easiest. Scrape, file, sponge. Do not use heat.
Soft plastic and PVC (board game minis, some pre-assembled figures). A sharp blade shaves it; a dull one drags and leaves fuzz. Use very light passes and finish with a fine sponge. Some people lightly warm the seam; that works but is easy to overdo, so scraping is the safer default.
Resin (3D-printed and cast). Resin dust is not something you want to breathe: work with a mask and wet-sand where you can. Resin files and sands easily but chips at thin edges, so support the part. For batches of printed miniatures, a powered sander saves hours: the DSPIAE ES-A reciprocating sander runs at three speeds with several head shapes and about 100 minutes per USB-C charge, with low vibration for control on delicate parts. Our review covers where it is worth it and where a sponge is still better.
Metal (white metal, pewter). Files only, light touch. White metal alloys may contain lead: file, never power-sand, keep the dust off your work surface and wash your hands afterwards. Metal mold lines are usually larger and sit on flash that you can first trim with the knife.
Hair, fur, textured cloaks and other nightmares
Flat surfaces are easy. Mold lines through hair or fur are the ones people give up on. Three approaches:
- Re-cut the texture. Scrape the line flat, then use the corner of a tapered file or a fine blade tip to re-scribe the hair strands across the flat spot in the same direction as the sculpt. Done lightly, it disappears under paint.
- Hide it. If a line runs through a texture you cannot re-cut, a thin coat of liquid putty or a tiny amount of filler, sanded, will give the paint something consistent to sit on. See How to Fix Gaps and Seams.
- Leave it and shade it. On rank-and-file troops that will be viewed at arm's length, a wash will hide a faint line in hair better than an over-filed smooth patch.
Holding the model while you work
Most gouges happen because the model slipped, not because the tool was wrong. Two cheap fixes: a rotating painting vise with magnetic base holds a figure or base at 0, 30 or 60 degrees and turns while you work both hands; and for separate tiny parts (heads, weapons, shoulder pads) a sticky clay pick-up pen holds them firmly enough to scrape without your fingers in the way.
Order of operations for a squad
- Clip all parts from the sprue, cutting away from the part (the two-cut method).
- Remove mold lines on every part before assembly: once a torso is glued to legs you cannot reach half the seams.
- Assemble, fill any gaps, sand the joins.
- Wash in soapy water, dry, prime.
- Paint. If you use a wet palette, set it up now: How to Use a Wet Palette.
FAQ
Do I really need to remove mold lines?
For display pieces, yes, every one. For gaming armies, remove the obvious ones on faces, weapons and large flat surfaces; a faint line in a crease will not show on the table.
Can I use sandpaper instead of a knife?
On flat areas, yes: a fine sponge works. On curved surfaces and next to detail, a scraped edge is more precise because it removes only the raised seam.
What grit for mold lines on plastic miniatures?
After scraping, #600 to #1000 to blend, finer only on smooth armor. The full grit logic is in How to Sand Scale Models.
Is an electric sander overkill for miniatures?
For a handful of plastic minis, yes. For resin prints, vehicles, or 30-model armies, it pays back in time and consistency.
Tools mentioned in this guide
- Tapered Metal Files #150-#400 - reach into corners and recesses without flattening nearby detail.
- #320-#5000 Sanding Sponges (Hobby Mio) - blend the scraped area into the surrounding texture.
- Sanding Matchsticks - beveled tip for grooves and creases.
- DSPIAE ES-A Electric Reciprocating Sander - saves time on resin prints and large batches.
- Miniature Parts Pick-up Sticky Clay Pen - holds tiny parts while you scrape.
- Rotating Painting Vise with Magnetic Base - holds and turns a figure at 0, 30 or 60 degrees.
- Hobby Knives, Blades & Saws and Miniatures & Wargaming collection
Everything for prepping and painting minis is in the Miniatures & Wargaming collection.