What is the best filler for plastic model seams?

Tamiya Basic Putty is excellent for general gap filling. Mr Surfacer 500 (liquid) is better for fine seam lines. For large gaps, use Milliput or epoxy putty. CA glue with accelerator works well for small gaps and is sandable.

How do I fill seam lines properly?

Apply filler along the seam line, pressing it into the gap. Let it cure fully (check the product instructions). Sand with progressively finer grits: 400, 600, then 800. Check for pinholes under primer and re-fill if needed.

How many sanding passes are needed?

Typically 2-3 passes. First pass with 400 grit to shape, second with 600 to smooth, third with 800 or finer for final finish. Each pass may reveal new pinholes that need filling. Prime between passes to check your work.

Should I use liquid or putty filler?

Use liquid filler (Mr Surfacer) for fine hairline seams and surface imperfections. Use putty for wider gaps (over 0.5mm). Use epoxy putty for structural filling and reshaping. Each has its place in the modelling toolkit.

ModelCalcs

Filler Calculator — Seam Line & Gap Filling

Estimate putty or filler needed for seam lines, gaps and corrections on your plastic kit.

Number of Seams

Enter the total quantity

Avg Seam Length (mm)

Total length of seams to sew

Avg Gap Width (mm)

Width measurement

Filler Type

Select the type

Kit Fit Quality

Select the quality level

How We Calculate This

Calculates filler volume based on seam dimensions and kit quality, with an overfill allowance for sanding.

Formula

Gap volume = Total seam length x Gap width x Gap depth
Adjusted volume = Gap volume x Kit quality factor
Total needed = Adjusted volume x Overfill factor (1.5-2x for sanding waste)

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates. Always verify quantities before purchasing materials.