How to Fill Gaps on Scale Models (Beginner Friendly Guide from AFV Hobby Hub)

Below is a complete, practical guide from AFV Hobby Hub on to how to fill gaps on scale models, with clear steps, tool options, and when to use each method. (You can find the Best Fillers for Scale Modeling here)

1. Identify the type of gap

Not all gaps are the same. Before choosing a filler, figure out what you’re dealing with:

• Hairline seam
• Medium gap (0.5–1 mm)
• Large gap or misalignment
• Step (one side higher than the other)

Each type benefits from a different filler.

2. Choose the right filler

A. Thin Gaps → Liquid Cement + Pressure

For tiny seams, you can often “weld” the plastic together.

• Apply liquid cement
• Press the joint until melted plastic oozes out
• Let cure
• Sand smooth

This is the cleanest method because the filler is the plastic itself.

B. Small to Medium Gaps → Modeling Putty

Putty is easy to apply and sands well.

Best for:

• Gaps around hatches
• Wing roots
• Turret seams

Pros: Easy to use Cons: Can shrink as it dries

C. Thin, Precise Gaps → CA Glue (Super Glue)

CA glue is perfect for hairline gaps or areas needing crisp detail.

Pros:

• Doesn’t shrink
• Sands very smooth
• Great for re‑scribing panel lines

Cons:

• Harder to sand if fully cured
• Sets quickly

Tip: Use baking soda or accelerator if you need instant curing.

D. Large Gaps → Plastic Shims or Sprue Goo

For big gaps, putty alone won’t cut it.

Plastic shims: Cut thin strips of styrene and glue them into the gap, then sand flush.

Sprue goo: Dissolve leftover sprue in liquid cement to make a thick plastic paste. A complete guide here

Pros: Bonds like real plastic Cons: Long drying time

3. Apply the filler correctly

Surface Putty

·        Putty Surfacers come with their own brush applicator

• Slightly overfill the gap
• Let dry fully for 24 hrs

Putty

• Apply with a toothpick or sculpting tool
• If necessary, it can be diluted with Extra Thin Cement (A.MIG-2025)
• Slightly overfill the gap
• Let dry 24 hrs

CA Glue

• Apply a thin bead along the gap
• Smooth with a gloved finger or tool
• Sand within 10–20 minutes for easiest shaping

Sprue Goo

• Brush into the gap
• Let cure overnight
• Sand like normal plastic

4. Sand the area smooth

Use progressive grits:

• 400–600: Shape the filler
• 800–1000: Smooth the surface
• 1500–2000: Polish for paint

Keep sanding localized to avoid flattening surrounding detail.

5. Re‑scribe lost panel lines

Filling and sanding often erase surface details.

Use:

• A scriber
• A rivet maker
• Scribing tape as a guide

Light, repeated passes work better than one heavy cut.

6. Check your work with primer

A thin coat of primer reveals:

• Remaining gaps
• Scratches
• Uneven surfaces

If you still see flaws, repeat the fill‑sand‑prime cycle. Even pros do this—it’s normal.

Common Mistakes to Avoid

• Using too much filler at once
• Sanding before the filler fully cures
• Over‑sanding and flattening curves
• Not priming to check your work
• Trying to fix huge gaps with putty alone

We hope this was helpful; AFV Hobby Hub