How do I build a plastic model kit properly?

The difference between a model that looks built and one that looks assembled is almost entirely in preparation — removing parts cleanly, cleaning up the moulding seams, and testing fit before anything is permanent.

Safety

What you'll need

• Sprue cutters or a sharp craft knife
• Plastic cement, not general-purpose glue
• Fine abrasive sticks or wet-and-dry paper
• A cutting mat

Step by step

1. Read the instructions all the way through first.Kits often want subassemblies painted before they are enclosed. Discovering that after gluing the fuselage together is a common and expensive lesson.
2. Cut away from the part.Snip the sprue gate a couple of millimetres from the part, then trim the remaining stub flush with a sharp blade. Cutting flush at the part pulls a divot out of the plastic.
3. Clean up the mould seams.The fine ridge along a part where the two mould halves met. Scrape it off with the back of a blade or a sanding stick. Leaving them is the most obvious mark of a rushed build.
4. Wash the parts if the kit is old.Warm soapy water removes mould release agent, which otherwise stops paint adhering. Let them dry fully.
5. Dry fit everything.Assemble each joint without cement and check it closes. Kits vary enormously in fit, and finding a gap now means you can plan for it rather than discover it under a set joint.
6. Use plastic cement, not superglue.Plastic cement is a solvent that melts and welds the two surfaces into one piece. It is far stronger than an adhesive layer. Superglue has its place for metal and clear parts, where cement would craze.
7. Apply cement sparingly with a fine brush.Capillary action draws thin cement along a joint you are already holding closed. Too much cement melts detail and squeezes out as a visible scar.
8. Paint subassemblies before enclosing them.Cockpit interiors, wheel wells, engine bays. Anything that becomes inaccessible after assembly should be painted and finished first.
9. Prime before painting.A thin coat of primer shows up every flaw while they are still fixable, and gives the colour coats something consistent to grip.
10. Build up paint in thin coats.Several thin coats, whether brushing or spraying. Thick paint drowns the surface detail that the kit maker spent money moulding.
11. Fill and sand seams before painting.Model filler into the joint, let it cure, sand flush, and re-scribe any panel line you lose. A visible seam under paint is the first thing anyone notices.
12. Start with a simple kit.A well-regarded kit with a low part count teaches the skills. A complex or poorly fitting kit as a first project usually ends in a box.

Tips

• Cut away from the part, then trim the stub. Never snip flush against the plastic.
• Plastic cement welds; superglue only sticks. They are not interchangeable.
• Paint anything that will become inaccessible before you close it up.

Common mistakes

• Twisting parts off the sprue — It tears the plastic and leaves a crater in the part that needs filling and sanding, often in a visible place. Sprue cutters and a knife cost very little.
• Using too much cement — The solvent melts the plastic, so an excess softens the surface, destroys fine moulded detail and squeezes out into a ridge that is much harder to remove than it was to avoid.

If it doesn't work

Questions people ask