Before reaching for putty, decide whether you have a seam that should close, a true gap caused by missing material, or an alignment problem. Filler is excellent when material is genuinely missing, but it should not be used to hide parts that simply do not fit correctly. Dry-fit first, correct the geometry, then choose cement, CA, putty or styrene according to the size and structure of the repair.
- Tight aligned styrene seam: plastic cement, cure, then sand.
- Small shallow gap: modeling putty.
- Small hard-edged gap where CA is suitable: CA can act as adhesive and filler.
- Large structural gap: consider styrene strip or sheet rather than a huge mass of filler.
- Irregular repair or sculpted area: epoxy putty can be useful.
Start with dry-fitting and alignment
If one fuselage half sits higher than the other, a layer of filler will not solve the underlying step. Check locating pins, tabs, warped parts and interference inside the assembly. Sand or adjust the contact points before gluing where necessary.
For the adhesive side of the job, see our scale model glue guide.
Hairline seams: let the joint do the work
When two styrene parts meet tightly, plastic cement can weld the joint. A small amount of softened plastic may squeeze out of a properly clamped seam; once fully cured, that material can sometimes be sanded flush without conventional putty. Do not start sanding while the plastic is still soft beneath the surface.
Small gaps: use putty selectively
For real gaps, ejection-pin marks and shallow surface defects, modeling putty is often the straightforward fix. Apply only enough to bridge the defect and slightly overfill the area so you have material to level after curing.
The 20g Quick Drying Black/White/Grey Putty, Multi-purpose Acrylic Putty and 30ml High-density Water-Based Putty are three catalog options for gap-filling work, but they have different formulations and handling characteristics. Treat them as different tools, not interchangeable tubes with identical behavior.
CA as a gap filler
Cyanoacrylate can fill some small gaps and cures harder than many conventional putties. That can be useful around crisp edges or when you want a repair that can be worked relatively cleanly after curing. It also means the filler may sand differently from the surrounding plastic, so avoid allowing a large ridge to build up.
20ml Black Super Glue is a black cyanoacrylate in the current catalog that is also described for gap-filling use.
Epoxy putty for larger or sculpted repairs
Two-part epoxy putty is useful when you need to shape material, rebuild an edge or fill an irregular void. The AB Epoxy Putty for Scale Modeling is intended for filling seams, repairs and sculpting. Remember that epoxy putty is a filler/sculpting material; it is not the same thing as the two-part epoxy adhesive discussed in the glue guide.
Large structural gaps: add material instead of endless filler
If a gap is wide or deep, packing it with putty can create shrinkage, long curing times and a weak edge. A strip of styrene fitted into the opening can provide structure, after which a much smaller amount of filler is needed to blend the repair. This is especially useful where a seam must preserve a straight edge.
Sand the repair progressively
Once the repair is fully cured, level the high spot rather than sanding a huge area around it. Start only as coarse as necessary, then move through finer abrasives to restore the surface. A rigid tool helps preserve flat planes; flexible abrasives are better around curves.
4pcs Sanding Sticks are useful for controlled progressive sanding. For tight spaces, Sanding Matchsticks can reach areas where a full-size stick is awkward. See also our technique guide on how to sand scale models.
Use primer as an inspection coat
A light primer coat can reveal scratches, pinholes and a seam that looked invisible on mixed colors of bare plastic and filler. If the defect is still visible, correct it before committing to the final paint. The purpose is inspection, not burying a bad seam under a thick layer of primer.
Protect nearby surface detail
Panel lines, rivets and raised detail are easy to flatten while chasing a seam. Keep the sanding area as narrow as practical and mask adjacent detail if that helps you control the abrasive. If a panel line crosses the repaired seam and disappears, re-scribe only after the filled area is stable enough to take the tool cleanly.
Common gap-filling mistakes
- Using filler to hide bad alignment.
- Applying far more putty than the gap needs.
- Sanding cemented styrene before the joint has cured.
- Using a soft sanding tool on a surface that needs to remain flat.
- Forcing putty into a large structural void that should receive a styrene shim.
- Treating epoxy putty as if it were epoxy adhesive.
- Skipping an inspection coat and discovering the seam after final paint.
Useful gap and seam products from Hobbyist Haven
| Product | Best fit in this guide |
|---|---|
| 20g Quick Drying Putty | Small gaps and molding defects |
| Multi-purpose Acrylic Putty | Gaps, ejection-pin marks and surface corrections |
| High-density Water-Based Putty | Gap filling and texturing |
| 20ml Black Super Glue | CA bonding plus suitable small gap-filling jobs |
| AB Epoxy Putty for Scale Modeling | Irregular fills, repairs and sculpted corrections |
| 4pcs Sanding Sticks | Leveling cured repairs through progressive grits |
FAQ
Should I use putty on every model seam?
No. A tight, aligned styrene seam may only need proper cementing and sanding after cure. Putty is for defects that still need added material.
Can super glue fill gaps?
CA can fill some small gaps, but it cures hard and behaves differently from conventional putty. Use it where that property helps the repair.
When should I use styrene strip?
Use added styrene when a gap is large or structural enough that a mass of filler would be inefficient or unstable.
