How to fill gaps in Warhammer 40,000 miniatures: plastic glue, two-part putty, brush-on filler and superglue methods, plus how to sand the join smooth before priming.
Even well-engineered kits leave the odd seam: the join down the middle of a torso, the line where two halves of a backpack meet, or a gap between an arm and a shoulder after a conversion. Primer and paint will not hide them. If anything, a wash pools in the gap and draws the eye straight to it. Most gaps take only minutes to fix once you match the filler to the size of the gap.
The short answer: for hairline seams on plastic, brush a little liquid poly cement along the join so the plastic welds together, then sand it flush once fully hard. For small gaps, use a brush-on liquid filler or a thin smear of two-part epoxy putty smoothed with a damp tool. For larger gaps or missing material, press in two-part putty, smooth it with water, let it cure overnight and sand. Always fill before you prime.
Why do gaps appear on miniatures?
Gaps come from slightly warped parts, mould lines left on the mating surfaces, uneven glue or simply the way a kit is split. Resin and metal parts gap more often than plastic because they can shrink or bend a little after casting. Dry-fitting every joint before glueing shows you where the problem will be while it is still easy to fix.
Which gap filler should you use?
Match the filler to the size of the gap and the material of the model.
| Filler | Best for | Sandable? | Working time |
|---|---|---|---|
| Liquid poly cement | Hairline seams on polystyrene plastic only | Yes, once fully hard | Seconds |
| Brush-on liquid filler | Very fine seams across texture, any material | Lightly | A few minutes |
| Superglue with bicarbonate of soda | Small gaps on resin and metal | Yes, but sets very hard | Seconds |
| Sculpting putty (yellow and blue) | Organic shapes, fur, cloth folds | Poorly; stays slightly flexible | Around 1–2 hours |
| Modelling epoxy putty (grey or white) | Larger gaps, hard edges, armour panels | Yes, files and sands cleanly | A few hours (check the pack) |
| Tube model filler | Wide, shallow gaps on vehicles and terrain | Yes | Minutes; shrinks as it dries |
How do you close seams with plastic glue?
On polystyrene kits, liquid poly cement softens both edges so they weld together, and squeezing the parts gently pushes a tiny bead of molten plastic out of the seam. Leave it to harden fully, ideally overnight, then scrape or sand the ridge flush. This removes the gap rather than filling it, which is why it gives the cleanest finish on smooth armour. Our guide to glueing miniatures explains which glue suits which material.
How do you fill a gap with two-part putty?
Mix equal amounts of the two parts until the colour is completely even with no streaks, then press a thin sausage into the gap with a metal sculpting tool. Keep the tool and your fingertips damp with water so the putty does not stick, and smooth it level with the surrounding surface. Remove the excess while it is soft; that is far easier than sanding hard putty later.
How long does putty take to cure?
Most two-part epoxy putties stay workable for one to a few hours and are fully hard after roughly 24 hours at room temperature, though brands vary, so check the pack. A warm room speeds curing and a cold workshop slows it noticeably. Do not sand, prime or handle the filled area until it has set, or you will drag soft putty out of the gap.
How do you fill fine seams on detailed areas?
Where a seam runs across fur, hair, cloth folds or chainmail, a brush-on liquid filler applied with an old brush is easier than putty because it flows into the line and leaves the texture intact. Apply thin coats and let each one dry; a single thick coat shrinks and cracks. If the seam crosses heavy detail, it is often quicker to re-sculpt a fold or a strand of fur over it with a little sculpting putty.
How do you sand filled gaps smoothly?
Use fine sanding sticks or wet-and-dry paper around 400 to 800 grit, wrapping it round a cocktail stick for tight spots. Sand only the filled area so you do not soften the surrounding detail, then wipe away the dust and check under a strong light. Taking off mould lines before assembly also cuts down how much filling you need.
Should you fill gaps before or after priming?
Before. Primer can struggle to grip some putties until they are fully cured, and a patch filled after priming has a different texture that shows through paint. If you only spot a gap once primed, fill it, let it cure and spot-prime that area before carrying on; see how to prime miniatures.
How do you stop gaps forming in the first place?
Dry-fit every part, clean the mating surfaces with a file or sanding stick, and hold joints with clamps, elastic bands or poster putty while the glue sets. On heavy metal or resin parts, a pin makes a stronger joint that is less likely to open over time; our guide to pinning miniatures shows how. If a gap still shows after painting, the fixes in our painting mistakes guide will help you blend the repair.
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Related reading
- How to Use Green Stuff on Warhammer 40,000 Miniatures: Sculpting Basics
- How to Pin Warhammer 40,000 Miniatures for Stronger Joints
- How to Glue Warhammer 40,000 Miniatures
- How to Remove Mould Lines from Warhammer 40,000 Miniatures
- How to Make Urban Rubble Bases for Warhammer 40,000 Miniatures
- Warhammer 40,000 Hobby Guides & Free Tools