Putty & Fillers

Putty and Fillers for Gundam Models: The Complete Guide to Flawless Finishing

Every serious modeler eventually reaches the moment when a bare plastic kit is no longer enough. You want clean, seamless surfaces. You want sink marks gone. You want the two halves of a shield to read as a single solid piece instead of two shells snapped together. That is where putty and fillers step in. They are the quiet workhorses of the hobby, the products that separate a good build from a genuinely professional one. This collection brings together the lacquer putties, epoxy putties, and specialized fillers that let you erase imperfections, sculpt new detail, and take your Gundam models from stock assembly to contest quality.

Whether you are tackling your very first seam line or you are a veteran who scratch builds custom armor, understanding how these materials behave will save you hours of frustration and a great deal of wasted plastic. Below you will find a thorough walkthrough of the main types of putty, when to reach for each one, and the core techniques that make them work. Pair the right filler with the proper method and you will wonder how you ever built without them.

Why Putty and Fillers Matter for Gunpla

Injection molded kits are engineering marvels, but they carry the fingerprints of their manufacturing process. Seam lines appear where mold halves meet. Sink marks form on the back of thick parts where the plastic cooled unevenly. Ejector pin marks leave shallow circles in hidden and not so hidden places. Small gaps open up between panels that were never designed to fit perfectly flush. None of these are flaws in your building skill. They are simply the nature of styrene molding, and they are exactly what putty exists to solve.

A filled and sanded surface does more than look clean. It reflects paint evenly, it holds a coat of primer without telegraphing every underlying blemish, and it gives you a canvas that actually deserves the time you spend airbrushing and weathering. Skipping this stage is the single most common reason a build looks unfinished even when the paint job itself is excellent. Once you commit to proper filling and seam removal, the jump in quality is immediate and obvious.

The Main Types of Putty

Lacquer Putty

Lacquer putty is the go to solution for shallow imperfections, fine surface work, and quick fixes. It comes as a thick paste, usually squeezed straight from a tube, and it cures by solvent evaporation rather than a chemical reaction. That means it dries fast, sands beautifully to a fine feathered edge, and blends seamlessly into surrounding plastic. Modelers reach for lacquer putty to fill sink marks, smooth over faint seam lines that survived initial sanding, and take care of tiny pinholes and scratches.

Because lacquer putty relies on evaporation, it shrinks slightly as it cures. This makes it perfect for thin applications but poorly suited to deep gaps, where the shrinkage would leave a sunken center that needs a second and sometimes third pass. The trick is to apply it in modest layers, let each one fully cure, and build up gradually rather than trying to jam a deep cavity full in one shot. Applied correctly, lacquer putty becomes nearly invisible once primed. It also thins readily with lacquer thinner, which lets you create a brushable surfacing putty for extremely smooth results across broad areas.

Epoxy Putty

Epoxy putty is a completely different animal, and it is the material of choice when you need volume, strength, and the ability to sculpt. It arrives as two separate components, a base and a hardener, that you knead together in equal parts. Once mixed, a chemical reaction begins and you have a workable window, often twenty minutes to an hour depending on the brand, during which the putty behaves like modeling clay. After that it cures rock hard with essentially no shrinkage.

That lack of shrinkage is the whole point. Epoxy putty fills deep gaps in one application, rebuilds broken or missing parts, and lets you add entirely new detail such as armor plating, mechanical greebles, cabling, or reshaped edges. You can smooth it with water or a wet tool while it is soft, press texture into it, and carve it once it hardens. Serious kitbashers and scratch builders lean on epoxy putty constantly because it turns a static kit into a genuine canvas for custom design. It bonds tenaciously to styrene, so anything you sculpt stays put through sanding, priming, and painting.

Polyester and Two Part Surfacing Putties

Sitting between the two extremes are polyester based putties and dedicated two part surfacing fillers. These cure hard and fast with minimal shrinkage, making them excellent for filling medium sized gaps and creating perfectly smooth surfaces over large panels. They sand cleanly and take primer well, offering a middle ground when lacquer putty is too thin for the job but full epoxy sculpting is more than you need. Keeping one of each type on your bench means you always have the right tool for whatever the kit throws at you.

Core Techniques That Get Results

Seam Removal

Seam lines are the most frequent target for putty work, and the cleanest results usually come from a combination of methods. For tight seams, cement and glue can weld the halves together so the melted plastic squeezes into the gap, and after curing you simply sand the ridge flat. For seams that stay slightly open, a thin bead of lacquer putty run along the line, then sanded back, erases the join completely. The goal is a surface where light passes over the former seam without catching any interruption. Take your time here, because seam removal done right is invisible and seam removal done poorly is the first thing a trained eye notices.

Gap Filling

Gaps come in every size, from hairline splits to structural voids where parts were never meant to marry cleanly. Match your material to the depth. Shallow gaps take lacquer putty. Deeper ones want epoxy or a two part filler that will not sink as it cures. Overfill slightly so you have material to sand down to a flush surface, and always let the putty cure completely before you touch it with abrasives. Rushing this step drags soft putty out of the gap and forces you to start over.

Sculpting and Adding Detail

This is where epoxy putty turns you from a builder into a designer. Knead a small batch, apply it to the area you want to reshape, and work it while it is soft using sculpting tools, dental picks, or simply a wet fingertip. You can extend armor, close panel lines, build custom weapon housings, or add mechanical detail that makes a stock kit look like a one of a kind creation. Once cured, refine the shape with hobby knives, files, and progressively finer sandpaper until the new geometry flows naturally into the original part.

Sanding and Surface Prep

No putty technique is complete without disciplined sanding. Start with a coarser grit to knock down the bulk of the cured material, then step through progressively finer grits to feather the edges and polish the surface. Sanding under running water, known as wet sanding, keeps dust down and produces a glassier finish on the final passes. The quality of your sanding directly determines whether your filler work disappears or announces itself. This is the stage where patience pays the biggest dividends, and it connects directly to the broader set of hobby tools every modeler needs on the bench, from sanding sticks to needle files.

Building Your Filling Workflow

A repeatable workflow keeps your results consistent from kit to kit. The following sequence works for the vast majority of builds:

• Assess before you assemble. Dry fit parts and mark every seam, sink mark, and gap you intend to address. Fixing problems is far easier before the surrounding detail gets in the way.
• Choose the right filler. Reach for lacquer putty on shallow blemishes, epoxy putty on deep gaps and sculpting, and a two part surfacing filler for everything in between.
• Apply in controlled amounts. Overfill slightly rather than trying to hit the exact level, and build deep fills in layers to manage shrinkage.
• Cure fully. Respect the curing time. Sanding soft putty ruins the fill and wastes your effort.
• Sand progressively. Work from coarse to fine grit, wet sanding the final passes for the smoothest surface.
• Prime to reveal. A coat of primer exposes any spots that still need attention, so you can catch problems before final paint.

Follow this loop and every kit you build will carry the clean, seamless surfaces that mark a genuinely finished model. It becomes second nature quickly, and the payoff shows in every reflection off a freshly painted panel.

Priming After Filling

Filling and priming are inseparable partners. Once your putty work is sanded smooth, a coat of surfacing primer does two jobs at once. It gives paint a uniform surface to grip, and it acts as a diagnostic layer that reveals any remaining scratches, ghost seams, or micro pinholes that were invisible on bare and multicolored plastic. If the primer exposes a flaw, you spot fill, sand again, and reprime that area. Skipping straight from sanding to color paint almost always means discovering leftover imperfections after it is too late to fix them cleanly. Investing in quality primers is the natural next step after your fillers, and the two products together form the foundation of every professional finish.

Choosing the Right Products for Your Bench

The best approach is to stock a small range so you are never caught without the correct material. A tube of fine lacquer putty handles daily seam and sink mark work. A set of epoxy putty covers deep fills and any custom sculpting ambitions. A two part surfacing filler bridges the gap for larger smooth panels. Add a solid selection of sanding tools and a quality primer, and you have a complete finishing station that will carry you through beginner kits and master grade projects alike.

Think of these materials as an investment in every future build rather than a purchase for a single kit. Putty keeps for a long time when stored properly, and the techniques you learn transfer to every model you ever make. The modeler who masters filling and finishing produces work that consistently stands out, whether displayed on a shelf or entered in competition.

Take Your Builds to the Next Level

Flawless surfaces are not reserved for the pros. They come from the right materials, a repeatable process, and a willingness to slow down at the finishing stage. The putties and fillers in this collection give you everything you need to erase seams, fill gaps, and sculpt custom detail that turns any kit into something distinctly your own. Browse the selection, pick the products that match your current project, and start building models that look the way you always imagined they could.

Ready to complete your workbench? Explore our full range of hobby tools for the sanding sticks, files, and cutters that pair perfectly with filling work, stock up on quality primers to reveal and protect your surfaces, and grab the cement and glue that makes seamless seam removal possible. New to the hobby or planning your next build? Check out our guide to the best Gundam model kits to find the perfect canvas for your newly sharpened finishing skills. Add the right putty to your collection today and give every model the professional finish it deserves.