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Dents & Dings – Discounted Model Kits & Hobby Items with Box Damage
$8.06 $11.00 ~ $180.00How to Remove Model Parts From Sprues Cleanly and Eliminate Nub Marks
Tools and setup
- Nippers: Use a sharp pair for separating parts. Single-bladed (flush) nippers are ideal for the *final* cut, but any decent nippers work if you avoid cutting flush immediately.
- Hobby knife: For controlled shaving of leftover nub material.
- Sandpaper/sanding sponges: A small range of grits for smoothing and blending (progressive grits matter more than brand).
Clean part removal from runners (avoid stress marks)
The most common causes of “white” stress marks are twisting parts off the runner or trying to cut perfectly flush in one go. The goal is to minimize stress in the plastic and leave yourself a small amount of material you can remove cleanly.
- Never twist or snap parts off the runner. This flexes the plastic at the gate and almost guarantees whitening.
- First cut: separate the part from the runner with the cut away from the part. Leave a small “nub” (gate material) on the part instead of cutting flush.
- Use the two-cut method for stress-sensitive areas (thick gates, dark plastic, visible surfaces):
- Cut 1: Cut the gate several millimeters away to free the part.
- Cut 2: Use single-bladed nippers for a closer cut, but still leave a thin sliver to remove by knife/sanding rather than trying to nip perfectly flush.
Why this works: cutting flush can pinch and tear the plastic fibers at the surface, which both leaves dents and creates internal stress that shows up as white marks. Leaving material to remove later avoids that sudden stress.
Removing nub marks (knife + progressive sanding)
Trying to clip the nub perfectly flush is where dents, gouges, and stress marks happen. A cleaner approach is controlled removal followed by blending.
- Trim the remaining nub carefully.
- Use a hobby knife to shave it down in light, controlled passes.
- Keep the blade shallow and let it skim the nub—don’t pry or dig into the surrounding surface.
- Sand the nub down flush using progressive grits.
- Start around 600 grit, then move to 800 → 1000 → 1500.
- Use multiple light passes rather than heavy pressure. Let the abrasive do the work; pressing hard can create low spots, flat areas on curves, or uneven sheen.
- Blend the finish.
- Sand slightly beyond the nub area to feather the transition so it doesn’t look like a “patched” spot.
- On curved armor, follow the curve with the sanding motion to avoid accidentally flattening it.
Common mistake: jumping straight to a coarse grit (or pressing too hard) can remove surrounding detail and make the repair more noticeable than the nub itself.
Preparing parts for assembly (especially joints)
A good build is about fit: parts should assemble securely without forcing.
- Aim for snug, not tight. If a peg or joint requires noticeable force, it’s too tight and may stress-whiten during assembly or even stress-crack over time.
- Adjust tight joints gradually:
- Sand the peg/joint lightly with 400–800 grit sandpaper or a sanding sponge.
- Test fit after a few passes, then repeat until the tolerance feels right.
Tip: remove a tiny amount at a time—over-sanding a joint can make it loose, which is harder to fix cleanly.
Managing and disguising stress marks
Even with good technique, some whitening can appear—especially on dark plastic or thick gates.
- Prevention is best: leaving material to sand (instead of cutting flush) generally produces the least stress.
- Reduce visibility (“reverse stressing”): gently pressing on the white mark can sometimes lessen it by re-compressing the plastic.
- Marker touch-up: rubbing a gray or black fine-tip marker (for example, Gundam marker-style fine pens) into the stress mark can make it less noticeable from normal viewing distance. Choose a tone that matches the plastic—an unmatched marker can make the spot stand out more.
Limitation: sanding smooths the surface, but it won’t reliably remove the *color change* from stress whitening.
When you need a perfect finish
- Painting is the only 100% solution for fully eliminating nub/stress visibility, because it covers both discoloration and any sheen differences left by sanding.
- If you plan to paint, expect to prime and paint the whole part for a uniform finish.
- Avoid nail polish as a cover-up—it typically looks worse and can stand out more than the original mark.
Quick workflow checklist
- Cut away from the part → closer cut leaving a sliver → shave with knife → sand 600→800→1000→1500 → test fit joints and adjust with 400–800 → optional marker touch-up or paint for a flawless result.