Preparing Miniatures for Painting: Cleaning, Priming, and Fixing Common Errors

Quick answer

Prep in three steps: scrape and sand mold lines while the model is still in parts, wash resin and metal parts in warm soapy water, then prime in thin coats from 6–8 inches away. Do not prime in high humidity or extreme cold, and never spray on a bare, dusty surface. If you see fuzz or clumps, stop and strip the primer before it cures.

You have assembled your squad, the glue is dry, and you are ready to paint. Then the first coat of primer goes on and everything looks wrong: fuzzy details, a gritty texture, or paint that beads up and flakes off. Almost every one of these problems starts before the brush ever touches the model.

This guide walks through the prep stage in order, from cleaning mold lines to washing release agent off resin, and then covers the most common priming failures with a clear fix for each. It also tells you when to stop and start over rather than keep painting over a bad surface.

Start with clean parts, not a finished model

The easiest time to remove mold lines and flash is before assembly. A mold line left on a cloak or a bare arm will show through every layer of paint, and trying to scrape it later risks damaging nearby detail. Work over a tray or a sheet of paper so plastic shavings do not spread across your desk.

Use the back edge of a hobby knife or a dedicated mold line remover, dragging it along the line at a shallow angle rather than digging in. Follow up with a fine sanding stick or a small file. For hard-to-reach areas, a stiff brush and a little water will lift dust out of the crevices before you prime.

• Scrape in one direction, not back and forth, to avoid gouging the surface.
• Check the model under a bright lamp after sanding; angled light reveals lines you missed.
• Wash plastic parts with warm water and dish soap if they feel slick or have visible dust.

Washing resin miniatures and metal before paint

Resin and metal parts often carry a release agent or oil from the casting process. If you skip the wash, primer can bead up and pull away from edges, and paint will chip off in sheets later. Fill a bowl with warm water and a few drops of mild dish soap, then scrub each part gently with a soft toothbrush.

Rinse thoroughly in clean water and let the parts air-dry completely on a paper towel. Do not use hot water on resin, as it can soften fine details. If you are working with a used miniature that already has paint on it, stripping is a separate job; this guide assumes you are starting from bare plastic, resin, or metal.

• Warm, not hot, water protects resin detail.
• Let parts dry fully; trapped moisture under primer causes blistering.
• If water still beads on the surface, wash again with a fresh drop of soap.

Priming miniatures: thin coats, right distance, right conditions

Shake the can for a full minute after you hear the mixing ball rattle. Hold the model about 6 to 8 inches away and spray in short bursts, starting the spray off to the side and sweeping across the model. One light pass from multiple angles beats one heavy coat every time. You are aiming for a thin, even layer that still shows the model's detail.

Temperature and humidity matter more than most people expect. High humidity can make primer dry with a chalky, fuzzy texture, while cold weather can cause it to clump or fail to adhere. If you cannot spray outside, a well-ventilated garage or a spray booth near an open window works, but never spray in a closed room.

• Spray in short bursts, not one long blast.
• Let the first coat dry before adding a second; tacky primer attracts dust.
• Test on a spare piece of sprue before committing to a whole squad.

Brush-on primer as a backup

If the weather is against you or you live somewhere you cannot spray, brush-on primer is a reliable fallback. It goes on thinner than spray and gives you more control around fine details, though it takes longer on large models. Apply it in thin layers and let each dry before adding another.

Brush-on primer is also useful for touch-ups after assembly, where spray might not reach inside a cloak or under an arm. Keep a dedicated brush for primer; it is hard on bristles and you do not want to mix it with your detail brushes.

• Use a cheap synthetic brush for primer.
• Two thin coats beat one thick coat.
• Let it cure fully before painting; a tacky surface will lift paint.

Troubleshooting prep problems: symptom, cause, fix, and when to stop

• Fuzzy or gritty primer: Usually caused by spraying in high humidity or holding the can too far away, so the primer dries in the air before it lands. Fix: strip the model and re-prime in lower humidity, closer to the model, in thinner passes. If the fuzz is light, a soft toothbrush can knock off loose particles; if it is heavy, strip and start over.
• Paint beads up or pulls away from edges: Release agent or oil left on resin or metal is the most common cause. Fix: wash the parts again in warm soapy water, rinse, dry fully, then re-prime. If beading continues after a second wash, the surface may be contaminated; strip and clean again before painting.
• Mold lines visible after priming: Lines were missed during scraping, or the primer coat is too thick and hides the surface. Fix: scrape the line carefully with a fresh blade, sand smooth, and spot-prime. If the line runs through fine detail, stop scraping and consider a thin wash or a small file instead of risking damage.
• Primer clumps or spits: The can was not shaken enough, the nozzle is clogged, or the temperature is too cold. Fix: warm the can in lukewarm water for a few minutes, shake for a full minute, and clear the nozzle. If clumps have already landed on the model, let them dry and sand them down rather than trying to wipe wet primer.

Products that help at the prep stage

• Citadel: Air Calgar Blue (24Ml): Due to distribution restrictions we are only able to ship this product to the United States. If you are outside the US, plan an alternative paint source or check local stock before you start a project that depends on this color.
• Necromunda: Goliath Weapons and Upgrades: Multipart plastic kit; hobbyists can arm their Goliath gang with some of the deadliest weapons available to House Goliath and have additional customisation options such as heads and arms to create a truly unique gang. Multipart plastic arms and heads are exactly where mold lines and sprue gates hide. Clean and dry-fit each piece before you prime so you are not scraping paint off later.
• Warhammer 40,000 Strike Squad HFZ-03: Secondhand Shop Product sales are final and sold as-is. Items are 'What you see is what you get' and are purchased exclusively from clients through our Secondhand Store Program. Used miniatures may arrive already assembled or partly painted. Inspect them before priming and decide whether they need stripping or just a wash and a fresh prime.

Good prep is boring, but it is the difference between a squad that paints cleanly and one that fights you at every layer. Clean the parts, wash resin and metal, prime thin, and stop early when something looks wrong. Your brushes, your paint, and your patience will all thank you.