How to Remove Gunpla Nub Marks Cleanly

Every Gunpla part is attached to its runner by small gates. Cut it off and you're left with a nub: a little bump, and sometimes a white stress mark around it. One nub doesn't matter much. A hundred of them across a kit is the difference between "nice build" and "wow, is that painted?"

Here's how to cut parts cleanly, sand nubs away, and hide the white marks, using tools that cost less than a kit.

What causes nub marks?

• Leftover plastic: the bump left when you cut too far from the part.
• Stress marks: white or cloudy patches where the plastic was bent or crushed. Twisting parts off the runner and cutting with dull or thick blades cause them.
• Gouges: small dips where a cut went too deep into the part.

Good cutting prevents almost all of it. Sanding takes care of the rest.

Step 1: the two-cut method

1. First cut, far away. Cut the gate a few millimeters away from the part. This frees the part without putting stress on it.
2. Second cut, close. Turn the nippers so the flat side of the blade faces the part, then trim the remaining gate as close as you can without biting into the part.

Do this for every part on HG and up, even the ones that will be hidden. On a clear or light-colored part, it's what keeps the plastic from turning white.

Use sharp hobby nippers made for plastic. The Bandai Spirits Entry Nipper is a great first pair. Scissors and nail clippers crush the plastic and leave bigger marks.

Step 2: sand the nub flush

1. Start with a medium grit to knock the nub down. Sand in one direction with light pressure, keeping the stick flat against the surface.
2. Stop as soon as it's level. Over-sanding creates a flat spot on curved parts.
3. Finish with a finer grit to smooth out the scratches.
4. For a glossy part, finish with the finest grit you have, or a polishing stick, until the shine comes back.

The Bandai Spirits Model Sanding Stick Set is made for exactly this.

Curved and small parts

On a rounded part, roll the sanding stick along the curve instead of pressing flat. For small parts, hold the part in a clip or between your fingers and move the part across the sanding stick instead.

Optional: a hobby knife for stubborn nubs

Some builders shave the last bit of a nub with a sharp hobby knife before sanding. Hold the blade nearly flat against the part and take tiny slices, always cutting away from your fingers. It's fast, but it's also easy to dig in, so practice on a runner piece first.

Step 3: hide white stress marks

Even with good cuts, some plastics (especially red, dark blue and clear) show a faint white mark at the gate. A few ways to hide it:

• Sand and polish: often the white mark is only on the surface and sands right off.
• A marker touch-up: a matching color Gundam Marker over the spot. See Gundam Markers.
• Topcoat: a matte or semi-gloss topcoat evens out the whole surface, so sanded spots and light marks disappear. Browse topcoats in Paints.

Plan ahead: hidden gates and smart order

• Check where the gate is. Many modern kits place gates where they'll be hidden after assembly. You can skip perfect cleanup on those.
• Sand before panel lining. Sanding afterward can wipe off the line. Our panel lining guide covers the best order.
• Sand before stickers. Stickers on an unsanded nub never sit flat.
• Clean frame parts too. On RG and MG kits, nubs on frame joints can make transformations and joints stiff.

Grade by grade

Not sure which grade you're building? Our HG vs RG vs MG guide explains them all.

Common mistakes

• Cutting flush in one go. It stresses the plastic. Always cut twice.
• Using the nippers backwards. The flat side of the blade goes toward the part.
• Sanding in circles with heavy pressure. Light, straight strokes keep the surface flat.
• Using worn-out sanding sticks. Once the grit is smooth, it smears instead of sanding. Replace it.

Where your tools ship from

Items marked In stock ship from our Fort Lauderdale shop in 1 business day. Imported items arrive in 3 to 4 weeks (4 to 5 weeks to Puerto Rico and outside the continental US). Economy shipping is free over $75 in the continental US, Standard is $10, and Florida residents pay $5.

FAQ

Can I remove nub marks without sanding?

Mostly, yes. A careful two-cut method leaves very little behind. Sanding is what makes it invisible.

What grit should I use for Gunpla?

Use a medium grit to remove the nub, then a fine grit to smooth it, and the finest you have for glossy parts. A sanding stick set with several grits covers all three.

Why does my plastic turn white when I cut it?

That's stress whitening from bending or crushing the plastic. Cut a few millimeters away first, then trim close with sharp nippers.

Do I need to sand every nub?

No. Skip the ones that will be hidden after assembly and focus on the visible surfaces.

Just starting out? Read New to Gunpla and our Gunpla tools guide.