Nub Marks Are Ruining Your Kits. Here's How to Actually Fix Them.

By KitReviewerApr 24, 2026⏱ 6 min read💬 43 comments0

There's a specific kind of pain that every Gunpla builder knows. You pull a part off the runner, clip the nub, and there it is — a white stress mark, dead center on the most visible surface of the piece. You try to ignore it. You can't. It haunts you every time you look at the shelf.

Here's how to actually deal with it.

Step One: Cut Twice, Not Once

The biggest mistake beginners make is cutting the part directly off the runner in one clip. The stress from that one cut is what causes the white mark. Instead: cut the part off leaving a small nub attached — maybe 1-2mm. Then come back with a second cut, flush to the surface. Two cuts, no stress marks. This single habit change will transform your builds.

Yes, it takes longer. Yes, it's worth it. Every time.

Step Two: Sand It Down

For the second cut, you're aiming flush but you'll rarely be perfect. A small amount of leftover nub or a slight roughness is normal. 400 grit sandpaper, then 800, then 1000, working the spot in small circles. You're not aggressive here — just smoothing. On dark runners especially, this will remove the whiteness and restore the color.

Step Three: Polish or Gundam Marker

After sanding, the area will be slightly matte and lighter than the surrounding plastic. Two options: hit it with a Gundam Marker in the matching color and wipe most of it off (leaving just a stain), or use a plastic polish like Tamiya Polishing Compound to restore the original sheen. The marker method is faster, the polish looks more natural — your choice.

The Nuclear Option

Stubborn nubs on visible surfaces that nothing else fixes? Heat. A lighter held about 3cm away for literally one second will slightly melt the surface and fill the mark. This requires confidence and a steady hand. Practice on a sprue first. When it works, it's magic. When it doesn't, you've got a new problem.

Most of the time, two-cut plus sanding is all you need. Don't overcomplicate it.

The Ultimate Panel Lining Confession

The single biggest mistake new builders make: trying to panel-line their first kit immediately. Don't. Build the kit. Take a photo. Then practice panel lining on a cheap HG kit you don't care about. Then come back to your first kit later.

Panel lining is a skill. It takes 5-10 attempts before it clicks. Save your favorite kits for when the technique is solid.

The Tools That Actually Matter

Three things: Gundam Marker (gray for HGs, black for MGs/PGs), a sanding sponge, and patience. Premium tools (god-hand nippers, professional sanding sticks, color paint sets) help but are unnecessary for first builds.

The single most expensive thing worth buying early: god-hand nippers. ¥3,500. They reduce nub cleanup time by 80% on every kit you ever build. Worth it.

The Order of Operations

Build → top coat → panel line → decals → final top coat. This sequence prevents the most common rookie mistakes — silvering decals (skipped first top coat) and panel liner pooling (built without surface prep).

What Pros Don't Tell You

Most magazine-quality kits are repainted and weathered. The factory plastic finish, even when perfect, isn't what you see in published photos. The 'clean OOB' look is usually just a starter point.

This isn't a discouragement. It's clarification. Your kit doesn't need to look like the magazine; it needs to look like YOUR kit, finished how YOU want.

The Kit Sequence

Build cheap first. Build expensive later. The order is critical: HG → RG → MG → PG. Each step up assumes baseline skills from the previous tier.

Skipping ahead (jumping from HG to PG) leads to expensive frustration and sometimes broken kits.

The Single Best Advice

Build something. Don't research forever. Don't watch tutorials forever. Don't shop for tools forever. Buy a cheap HG kit, follow the manual, snap it together, put it on the shelf. Then build another one.

The hobby compounds quickly. Three kits in, you'll wonder how you ever found it intimidating.