Preparing Resin Models for Painting

You've just unboxed your first grey-resin kit. The parts look crisp, the detail is incredible, and every instinct is telling you to reach straight for the primer. Don't. There are a handful of preparation steps sitting between you and a finish you'll actually be proud of, and skipping any one of them will haunt you later — usually right after you've spent an hour painting.

This guide walks through every prep stage in order: cleaning, clean-up, gap-filling, pinning, dry-fitting, and priming. Work through them once and they become second nature. Rush them and you'll find yourself stripping paint off a figure you already fell in love with.

Why Washing Comes First — and Why It Actually Matters

Resin is cast in silicone moulds. To stop the cured resin from bonding to the mould, manufacturers apply a release agent — typically a thin film of silicone-based compound — before each pour. That release agent does its job well. Too well. It also prevents paint and primer from bonding to the resin surface, which is why a freshly primed figure can peel like a sunburn if you skip the wash.

The residue is invisible and has no smell. You cannot feel it by running a finger across the resin. There is no shortcut that detects it. The only reliable answer is to wash every single part before you do anything else, every single time, without exception.

How to Wash Resin Parts Properly

You don't need specialist products. Warm water and a small amount of dish soap — the kind you'd use for washing up — cuts through mould release agent reliably. Here's the method:

• Fill a bowl or container with warm (not hot) water and add a few drops of dish soap.
• Submerge all parts and use an old toothbrush to scrub every surface, paying particular attention to recessed detail, undercuts, and the insides of hollow pieces.
• Rinse thoroughly under running warm water until the water runs clear and there are no soap suds remaining.
• Pat parts dry with a lint-free cloth or paper towel, then set them aside on a clean surface and allow them to air-dry completely for at least two hours before moving on.

One wash is usually sufficient. If you're working with a kit that feels particularly greasy or oily to the touch, wash it twice. Resin absorbs very little water, so there's no risk of damage from soaking.

Removing Flash and Mould Lines

Once the parts are dry, examine them under a good light — a daylight bulb or a window is ideal. What you're looking for are mould lines (thin raised seams running around the part where the two halves of the mould met) and flash (thin membranes of excess resin, often found between fingers, around hair, or bridging gaps in the model's design).

Neither is a defect. They're normal artefacts of the casting process. Removing them cleanly is a core part of the hobby.

Tools You'll Need

• A sharp hobby knife — a fresh blade makes a significant difference. A dull blade drags and tears resin rather than cutting it.
• Needle files — a set with flat, half-round, and round profiles covers most situations.
• Wet-and-dry sandpaper — 400 and 600 grit are good starting points for resin.

The Technique

For flash, hold the part firmly and draw the blade across the membrane at a shallow angle, scraping rather than cutting. Thin flash often comes away cleanly in one pass. Thicker flash may need a few careful strokes.

For mould lines, the most controlled method is to hold the blade perpendicular to the line and draw it along the seam in short strokes — again, scraping rather than cutting. Follow with a needle file, then finish with wet-and-dry paper used wet. Sanding dry resin generates dust that you should not breathe; always sand wet, or use a dust mask.

Work slowly on areas with fine detail. Removing a mould line from a face takes patience, but it's far easier now than it will be once paint is involved.

Filling Gaps

Even well-cast kits produce small gaps at join lines when parts are assembled — a natural result of two surfaces that aren't quite perfectly flush. These gaps become much more obvious once primer goes on, when they catch light and shadow in a way they didn't when the resin was raw.

Greenstuff (a two-part epoxy putty) is the most common filler in the hobby because it stays workable for thirty to forty minutes, bonds well to resin, and can be smoothed with water and a silicone-tipped sculpting tool. Mix equal parts of the two components until the colour is uniform — marbling indicates incomplete mixing and uneven curing.

Press a small amount into the gap, smooth it level with the surrounding surface, and leave it to cure fully (usually overnight) before sanding back. If you overfill slightly, the excess sands away cleanly. If you underfill and sand through to the gap, add another thin layer. Superglue can fill very fine hairline gaps if applied carefully and allowed to wick in by capillary action.

Pinning for Strength

Resin is more brittle than plastic. Small contact areas — a wrist connecting a hand, an ankle connecting a foot, a thin weapon handle — are points of failure waiting to happen if they're held together by glue alone. Pinning adds a metal rod through both parts, turning a surface bond into a mechanical joint.

The process: drill a small pilot hole into both sides of the join using a pin vice, cut a short length of paperclip wire or brass rod to fit, dry-fit to check alignment, then glue the pin and close the joint. The pin doesn't need to be long — even 5mm of metal running through each side transforms the strength of the join considerably.

It's worth pinning any joint where the contact surface is smaller than roughly a fingernail, or anywhere the model will be handled regularly. Larger base contacts can usually get away with glue alone.

Dry-Fitting Everything Before You Commit

Before any glue is applied anywhere, assemble the entire model without adhesive and check that everything fits as it should. This is the stage where problems are free to fix. Once glue is involved, corrections cost time and sometimes parts.

Check for gaps that will need filling, parts that sit at a slight angle, and contact points that need additional material removed before they'll seat correctly. Make a note of the assembly order — some kits have parts that become inaccessible once adjacent pieces are glued. Assembling in the wrong sequence can make painting a section nearly impossible.

Priming

Primer does two things: it gives paint something to grip, and it reveals surface defects that weren't visible on raw resin. Apply a thin, even coat — multiple light passes from a can held about 25–30cm from the model, or a brush-on primer thinned to a milky consistency if you're airbrushing or prefer brush application.

Grey primer is the most versatile starting point because it's neutral. Black primer deepens shadows in recesses naturally; white primer makes colours pop, particularly useful for bright or transparent paints. Let the primer cure fully before assessing the surface — usually a minimum of an hour, ideally overnight.

Any gaps, mould lines you missed, or surface blemishes that primer reveals can be addressed now and spot-primed before painting begins.

Common Mistakes to Avoid

Mistake	Why It Causes Problems	The Fix
Skipping the wash	Primer and paint won't bond; flaking later	Always wash, always
Sanding dry resin	Resin dust is hazardous to inhale	Sand wet or wear a proper dust mask
Gluing before dry-fitting	Misaligned parts are difficult to separate cleanly	Dry-fit the complete model first
Thick primer coats	Fills fine detail; takes much longer to cure	Two or three thin passes rather than one heavy coat
Skipping pins on small joins	Resin joints break under normal handling	Pin anything with a small contact area
Rushing between stages	Wet parts don't hold primer; uncured putty deforms	Let each stage cure or dry fully

Getting the Right Tools

None of this requires an expensive setup. A hobby knife, a small set of needle files, some wet-and-dry paper, Greenstuff, superglue, and a rattle can of grey primer will cover every stage above. If you're looking for tools and materials to build out your prep kit, the accessories collection is a good place to start.

If you have questions about a specific kit or aren't sure how to approach a tricky join or unusual material, the contact page is there — no question is too basic. Getting the prep right is worth asking about.