Choosing A Sandpaper Grit Sequence For Smooth Gundam Finishes

A smooth Gundam finish begins long before primer or paint. Mould lines, nub marks, seam joins and small scratches all need to be reduced in stages, because one overly coarse abrasive can create damage that finer paper cannot quickly remove.

The right sandpaper grit sequence depends on the condition of the part, the plastic type and the finish you want. A bare snap-fit kit may need only light polishing, while a painted or scribed master-grade build requires a more controlled progression.

For Australian builders, useful supplies are easy to find through hobby shops, automotive retailers and stores such as Bunnings. The key is to treat grit numbers as steps rather than shortcuts: remove material efficiently first, then refine the surface until scratches are shallow enough for primer to hide.

Read The Surface Before Choosing Grit

Start by inspecting the part under a strong desk lamp. A 240 or 320 grit sanding stick can remove a prominent nub, heavy seam or excess putty, but it should touch only the affected area. On a clean, nearly flush gate mark, 400 or 600 grit is safer and reduces the chance of flattening nearby curves.

The shape of the part matters as much as the number printed on the abrasive. Use flexible sanding sponges on rounded armour, narrow folded paper between mechanical details and rigid sticks on flat panels. A scribed master-grade project, such as this full Sazabi build log, shows why crisp edges and controlled surface preparation matter when detail will remain visible under paint.

Run a fingertip across the area after each pass, but do not rely on touch alone. Lightly brushing away dust and checking the panel against reflected light will reveal scratches, low spots and remaining nub shadows.

Build A Controlled Progression

A reliable sequence for general polystyrene parts is 320 or 400 grit, followed by 600, 800, 1000 and, when required, 1500 or 2000 grit. Do not automatically use every grade. Move up when the previous scratches have disappeared, and avoid jumping from 240 directly to 1000 because deep grooves may remain beneath a polished-looking surface.

Use light pressure and several strokes in one direction. When changing to the next grit, sand across the previous direction at a slight angle. This makes the old scratches easier to identify and prevents you from polishing over defects that still need attention.

Wet sanding is useful from about 800 grit upwards, particularly before gloss paint. It controls airborne dust and keeps abrasive paper from clogging. For resin parts, remove loose dust carefully and wear suitable respiratory protection; resin particles are hazardous and should not be treated like ordinary plastic shavings.

Match The Method To The Material

Styrene plastic responds well to sanding sticks, sponge abrasives and wet-and-dry paper. Softer areas can become rounded quickly, so support thin fins and avoid lingering at corners. For ABS joints, use moderate pressure and inspect frequently, since aggressive sanding can alter tolerances and produce a loose fit.

Resin conversion parts usually need a different approach. Begin around 240 or 320 grit only where casting blocks or major seams demand it, then progress through 400, 600 and 800 grit. A spray of grey primer can act as a flaw detector, exposing scratches that are difficult to see on pale resin.

Before painting, wash parts with mild detergent, rinse them thoroughly and allow them to dry. This removes sanding residue, skin oils and mould-release contamination. Builders in humid coastal cities such as Brisbane or Sydney may need extra drying time before priming, especially in a garage or enclosed hobby room.

Recommendations For Australian Workbenches

Australian conditions make dust control and ventilation especially important. Local work health and safety rules place strong emphasis on controlling hazardous dust, while crystalline silica controls are particularly relevant to engineered stone and construction work. Model plastic is a different material, but the same sensible habits apply: use extraction, avoid dry sweeping and wear a properly fitted mask or respirator when generating fine dust.

A hobby bench near a sunny window can also make surface inspection easier, although direct heat may warp thin parts or accelerate paint drying unevenly. Keep abrasives sealed in labelled bags, because humid air can soften paper-backed products and clog them with residue.

Practical habits for consistent results include:

• Keep separate sanding sticks for rough shaping and final polishing.
• Mark completed areas with a pencil so missed scratches remain visible.
• Use 600 to 800 grit before surfacer and 1000 to 2000 grit for smoother gloss finishes.
• Test the sequence on a spare runner before working on a prominent armour panel.
• Clean parts with a soft brush or compressed air before washing them.
• Record the grit that worked for each plastic, putty or resin brand.
• Photograph parts under angled light before applying primer.

Sharing these small discoveries strengthens the hobby community. Spaces such as Encourage Her Network also reflect the value of welcoming, practical knowledge exchange across different skill levels and backgrounds.

Check Progress Before The Final Coat

Primer should confirm your preparation rather than conceal careless sanding. Spray a thin coat, let it cure according to the product instructions and inspect it under angled light. If scratches remain, return to 800 or 1000 grit instead of using a very coarse abrasive that may cut through surrounding detail.

The best stopping point depends on the finish. A flat coat can disguise fine marks, while metallic and gloss paints magnify every uneven edge. Before displaying a finished build in the Display Case gallery, check panel lines, curved armour and exposed frame parts from several angles.

A weekend build schedule can help prevent rushed surface work; this realistic Gundam schedule makes room for curing and inspection rather than treating sanding as an afterthought.

Choose the coarsest grit that safely solves the visible problem, then advance gradually until the surface matches the intended paint finish. Share your tested sequences, photographs and work-in-progress discoveries on Gundam Eclipse so other builders can refine their own techniques.