Plastic cement vs super glue: which glue for which part

Plastic cement: for polystyrene plastic

Plastic cement is a solvent. It softens the surface of both polystyrene parts so they fuse into one piece as it evaporates. That makes it the default for injection-moulded plastic kits and plastic miniatures, and the joint can be as strong as the plastic around it.

Thin, flowing cements are applied after the parts are fitted together. Tamiya describes its Extra Thin Cement as made to flow into the small spaces between two plastic parts that have already been fitted to one another, using the pointed brush in the cap. You hold the parts, touch the brush to the seam, and the cement runs in.

Because it works by softening plastic, cement does nothing on resin, metal or a painted surface. Scrape paint off both faces of a join first.

Super glue: for resin, metal and mixed joints

Super glue (cyanoacrylate, or CA) bonds almost anything to almost anything, so it is the glue for resin, white metal, and joins between different materials, for example a metal head on a plastic body.

Reaper's assembly guide notes the trade-off: super glue is very good at resisting forces pulling two surfaces apart, but its bond has relatively poor shear strength, which is why heavier parts are pinned.

When neither is enough

For a heavy metal or resin part, or a joint that will be handled during games, drill both faces with a pin vice and glue in a short length of wire or brass rod. The pin carries the sideways load.

Where a pin will not fit, Reaper recommends five-minute two-part epoxy: slower to set, but much stronger than super glue in shear.

Quick chooser

Plastic to plastic: plastic cement.

Resin, metal, or different materials together: super glue, pinned if the part is heavy.

Large, heavy or stressed joint: pin plus super glue, or epoxy.

Clear parts such as canopies: neither cement nor ordinary super glue is ideal, as both can fog clear plastic. A PVA-type clear-parts glue is the usual choice (general hobby practice; check the glue maker's instructions).

Mistakes to avoid

Flooding a joint with cement. Excess solvent can soften and mark the surface next to the join.

Gluing primed or painted surfaces with cement. It needs bare plastic to work.

Leaving super glue uncapped. Keep a debonder on the bench for glued fingers or misplaced parts, but check what it is made of first: many debonders use a strong solvent that will also soften or mar polystyrene and other plastics, exactly like the cured super glue it is dissolving, so wear gloves, work in a ventilated space and follow the product's own label rather than assuming every debonder behaves the same way.