How to Paint 3D Prints: Primer, Airbrush, Masking and Brush for a Collectible Finish

Paint does not hide a bad surface. It shows it. Every scratch, pit and layer line comes back through the colour, sharper than before. So painting a print well is mostly the surface, then thin layers, then patience between them. The first layer of any colour looks bad. That is normal, and the people who panic and pile on paint are the ones who end up stripping it.

This is how I paint the resin figures I sell and the painted masters that go to factories: primer, base colours with an airbrush, masking and stencils, hand-painted details, sealer, then assembly.

The short version. Sand, filler primer, sand again, then two thin coats of a fine primer in the colour that suits the paint. Plan the colours before any paint touches the piece. Airbrush the base colours in thin layers, light colours before dark, the creases before the open surfaces, and let each layer dry before the next. Wait at least a night, better two, before any masking tape goes on. Hand paint what is not worth masking. Seal to set the sheen, part by part, then glue from the feet up.

Before any paint: the surface

Everything here starts on a part that has been sanded, filler primed, sanded again, washed and dried. How to get there is its own article: How to Sand 3D Prints

PLA prints take the same painting workflow. The difference is the sanding: PLA starts coarser, at 180 to 200 grit where resin starts at 400, and the filler primer does more of the work on the layer lines.

Mount the parts before any paint. Every part goes on a bamboo stick or a crocodile clip, standing in a cat scratcher, so nothing is touched again until it is dry. For thin or small parts I use metal rods with soft silicone tips; they hold without leaving the scar a clip's teeth do. Glue the stick into a connector or a face nobody sees, and stand it upright so it does not shadow the part. The best handle is one you sculpt in. I always mean to, and I always forget.

https://www.youtube.com/watch?v=Y_VI3MtchUc

The airbrush and the compressor

https://www.youtube.com/watch?v=t5AGRDZ9ysk

• Trigger or dual action. A dual action airbrush lets you control air and paint separately: that is the tool for highlights, shadows and fine detail. A trigger airbrush releases both at once, but it is far easier on the hand. Paint one piece and it makes no difference. Paint thirty and it does. Most of my base coats go on with a trigger airbrush now.
• Needle size. People say start with 0.3 or 0.35. I think 0.5 is more versatile: it sprays filler primer and the thicker clears as well as paint, and it forgives paint that is not thinned perfectly. If you can, buy one with several needles: 0.28 for detail, 0.5 for primer and base colours, 0.7 for clear coats and thick paint.
• Never mix the needle, the nozzle and the nozzle cap. Each size comes as a set. A 0.7 needle in a 0.5 nozzle is where the problems start.
• The compressor. One with a tank runs only when the tank needs filling; one without runs all the time. Empty the moisture trap now and then, so water does not reach the airbrush. Set the pressure with the airbrush open and empty, because the gauge drops the moment air flows.
• Pressure is not one number. It depends on the needle and the paint. My settings: 25 psi for the filler primer with a 0.5 needle, 20 psi for the fine primer and base colours with a 0.5, 15 to 20 with a 0.2 for stencils and detail. Test on a spoon first.

Primer: the colour under the colour

https://www.youtube.com/watch?v=hfXSz8zFFUU

The last primer coat is a fine one: Mr. Surfacer 1,000, 1,200 or 1,500, or Mr. Finishing Surfacer 1,500 in white or black. I thin it one to one with Mr. Color Leveling Thinner and spray it with the 0.5 needle at 20 psi.

1. Dust the part first. A quick, light pass from a little further away, from every side, so the next coat has something to grip.
2. Then thin layers, each one closer and slower. This coat stays on the piece, so no puddles. Keep the airbrush and the part moving; press, sweep, release.
3. Thirty minutes in the dehydrator at 45°C, then let the parts cool to room temperature before the next coat. A coat sprayed on a warm part can crack.
4. A second layer, a wet one. Then two to three hours in the dehydrator and the night to cure. Two layers is usually right; check in the morning whether anything needs a third.

Which colour. Grey is the default because it changes the paint least. Black under a dark piece: I am painting a character now that is ninety per cent black, so it got a black primer. White under bright colours. The same red is pinkish on white, the red in the bottle on grey, and a deep, blood red on black. Yellow on white is bright in one layer; on grey it turns green. A crease you missed on black reads as a shadow; on white, it shows.

Test on spoons. Sand a few plastic spoons, prime them the way you primed the piece, and paint them first. Scratch them, mask them, seal them. It is the cheapest way to learn what a paint does, and it keeps the mistakes off the figure.

The speck of dust

Unless you work in a lab, dust lands on wet paint. Check every part with magnifying glasses before the base colours. Do not scrape a speck off with a nail. Rub it with a micro fine sanding sponge, about 1,500 grit; it takes the speck and its mark without digging into the primer. If something lands between layers, stop: do not paint over it. Fix it, then prime again. A clean booth helps, and so does a damp paper towel nearby to catch some of the dust.

Choosing the paint

https://www.youtube.com/watch?v=4H8QC-Svjno

My rule: if a paint does not work over Mr. Surfacer, I do not use it. Within that, pick a brand with a palette that covers what you paint, and stay with it. Brands do not always mix; I have mixed Mr. Hobby with Tamiya and sometimes it worked.

• Tamiya acrylics, my favourite. A beautiful palette, strong pigment, easy to airbrush thinned with Mr. Color Leveling Thinner, workable with a brush. X is gloss, XF is flat. X21 Flat Base turns a gloss colour flat.
• Mr. Hobby, where I started. A palette close to Tamiya's, brush or airbrush.
• Vallejo, the first paint I ever used on a toy. Model Color for the brush, Model Air for the airbrush, thinned with water or their medium. Every colour you can think of and the best skin tone I know. Their large Premium bottles include candy colours, which go over a chrome or steel base for a coloured metal.
• MRP, pre-thinned and airbrush only. A small palette, mostly military, but the greens, the reds and the flat black are excellent.
• Alclad for metallics: chrome, steel, aluminium, eight kinds of gold. Always a mask, always the booth, always ventilation.
• Citadel for weathering: shades for old wood, leather and anything beaten up.
• Gaia Kaleido, new: pre-thinned, works over Mr. Surfacer, a huge palette.

The thinners, primers and clears that go with each: the equipment guide

Thinning. One to one for most Tamiya colours with a 0.3 to 0.7 needle; a little more thinner with a 0.2. Strong pigments take more: black, and a thick red. White and yellow need less. Test on a spoon before the piece.

Plan the colours first

Before any paint, I render the figure and try the colours on it. Any renderer works, even polypaint in ZBrush. Look up the paint makers' colours and use their codes, so the render uses paints you own or can buy. Then try lettering and logos on the render in a photo editor. A colour that looks wrong costs a click on screen and a stripped piece on the desk.

Three habits from the bench:

• Write the paints down, or photograph the bottles as you use them. Six months later someone orders the same piece and you will not remember.
• Mix more than you need. Matching a mixed colour again is close to impossible. On an edition, paint all of one figure's parts in a colour from the same mix, so a difference shows between two figures, not between a sleeve and its hoodie.
• Keep some paint unthinned for touch-ups with a brush after masking or gluing.

Base colours with an airbrush

0.5 needle, 20 psi, paint thinned one to one.

• Batch by colour, light to dark. White parts first, then beige, then the red, the green, the blue, black last. Clean the airbrush between colours, and the cap: a little red left in it turns the next white pink.
• Edges, creases and folds first, then sweep the open surfaces. Cover connectors and keys too, so a gap after gluing shows colour, not primer.
• The first layer is thin and looks bad. Red goes on looking pink. Do not chase it with more paint. I often lay the first layer in a similar colour I already have mixed: it saves the final paint and gives the creases a slightly different tone.
• The second layer is wetter, creases first again. Then a third if the colour needs it. On Bob the trousers took two layers, the hoodie three, the red beanie four. Dark colours rarely need more than three; yellow and white can take six thin ones.
• Use gloss white, not flat. It covers better and resists scratches. Change the sheen later with the sealer.
• Drying between layers: a few minutes in the air, then the dehydrator at 45°C, an hour or so for a first layer, one to two hours for a heavier second one, longer for each layer after. In a hurry: at least an hour between layers, then do not touch the piece for 48 hours. No handling, no masking, no decals, no sealer.

Why I paint mostly in gloss. Gloss paint is tougher and more resistant to scratches than flat, and the sealer sets the final sheen anyway. One catch: masking tape marks a gloss surface more easily, so give gloss paint longer before it is masked. The Bob parts sat four days.

Cleaning between colours: put the leftover paint back, rinse the cup with cheap thinner and a pipette, flush with a finger over the nozzle, then a rinse with window cleaner. At the end of the day, take the needle out, wipe it, and clean the nozzle with a cotton bud, one end wet, one dry. Paint left in the nozzle overnight clogs it.

Masking

Nobody likes masking. It is also how one figure gets clean colours where they meet. I split figures into as many parts as I can so I mask as little as possible.

The first rule: the paint must be dry. At least a night, 48 hours if you can. Test the tape on a painted spoon first.

• Tamiya masking tape is the only tape I have used that never left a mark. Keep several widths; cutting thin strips straight is harder than buying them.
• Flexible tape for curves and organic shapes, and for panel lines on hard surfaces. You can stretch it into place and cut it on the part, carefully, with a fresh blade on an Olfa cutter; its snap-off tip stays sharp.
• Masking putty for irregular shapes and large areas. It never leaves a mark and comes off clean. It droops if you leave it on, and it reacted badly with an alcohol based metallic on one of my pieces, so keep its edge off metallic paint.
• Construction tape and painter's tape with film only on top of Tamiya tape, never on the paint. The film covers large areas cheaply and the tape closes the gaps.
• Take the tack off. Stick a fresh piece of tape on your hand or your sleeve first, not on anything with lint. Cut it on a clean mat kept only for masking.
• Close every pocket. The airbrush's air finds any gap and blows paint into it. Tape the corners twice. It is never overkill.
• Never leave masking on for more than an hour or two after painting, and never put a masked part in the dehydrator. I have ruined parts doing exactly that.
• Peel slowly, each layer in the order it went on, most carefully over chrome.

Stencils for lettering and logos

Text and logos are a job for a vinyl cutter. Measure the space on the part, mock up the lettering on the render, make the artwork black and white, and cut it a few times over; the cutter and your fingers both spoil one now and then. Leave wide margins: you keep the frame and throw away the letters.

1. Weed out the letters, lift the stencil with transfer paper, and take some tack off on your hand. Vinyl grips hard.
2. Lay it on a dust-free surface, line it up, then mask everything around it.
3. A dusting layer, then a heavier one. For fine work I use a dual action airbrush with a 0.2 needle at 15 to 20 psi, close to the part.
4. Let it dry for 20 to 30 minutes, then peel. A blade and tweezers lift the vinyl; the inside of an O or a P is always the hard part. Then the dehydrator.

A spot of paint where it should not be comes off with a 1,200 or 1,500 sponge, the same fix as a speck of dust.

Hand painting the details

Some parts cost more to mask than to paint by hand: shoe panels, small logos, eyes. The brush also leaves a texture, which suits leather.

• Vallejo Model Air works with a brush. Thin it with an acrylic medium rather than water; it keeps the paint tougher.
• Brushes: I like a 10/0, a 1, sometimes a 5, and flat brushes. Start with cheap ones to find your sizes, then spend money on good ones.
• Mix properly. A mixing ball in each bottle, and a silicone tray as a palette: the dried paint pops out.
• Edges first, then fill. Do the edges with a fine brush while the paint is fresh in your mind, then fill. On the second layer, take a bigger brush: the edges are done and a big brush holds more paint. I bought tiny brushes for figures and used them twice.
• Thin layers, strokes in one direction. Thin layers hide the brush marks; thick ones show every stroke. The first layer always shows gaps. The second fixes them.
• Move the part, not your arm. Pull the brush towards you, move only your fingers, and turn the part under it. Plan how you will hold it: paint everything except the bit you are holding, let it dry, then turn it and finish.
• A hair dryer beside you dries water-based acrylic between layers in seconds. The dehydrator once the last layer is on, then the night before any sealer.
• Magnifying glasses, even if your eyes are good. The part gets bigger and your strokes get more confident.
• No black gloves. Paint on a black glove is invisible until it is on your piece.
• Lacquers by brush work differently. Mr. Color and Tamiya go on a little thicker, straight from the jar, with the brush softened in thinner. Dab the thinner off before a second layer, or it lifts the first.
• Split the small parts. Bob's eyes are separate pieces, so I can paint them in my hand instead of inside the head. Try the painted part in place before it is sealed.

Look after the brushes. Thinner, then water, after every session. Every month or two, a few minutes in a brush restorer, hanging so the tips do not touch the bottom, then a brush shaping gel. A good sable brush costs eight to ten dollars; looked after, it lasts years.

https://www.youtube.com/watch?v=1BwlDN556AY

Sealing

The sealer protects the paint from scratches and UV light, keeps the colours strong, and sets the sheen. This is why I paint in gloss: the sealer decides the finish, part by part.

• Sheens: matt, satin (semi-gloss), gloss, and ultra matt from some makers. Most paint brands make all of them. Some need thinning, Mr. Color Leveling Thinner again; Gaia Kaleido sprays straight from the bottle. Know whether yours is acrylic or polyurethane; they look the same in the bottle and are not.
• Layers set the sheen. Over gloss paint, one layer of matt gives a satin, three or four give a cloth matt. On Bob the hoodie and beanie got two layers of matt, the socks three, the soles one, because rubber has a little shine. The eyes, the coffee and the mug got three or four layers of gloss. Eyes need to look wet, and the gloss does the highlight a painted white dot would. The nose came out too plastic in gloss, so it got a layer of matt on top. You can always change a sheen once it is dry.
• Same object, same layers. A mug and its handle get the same number of coats, or they will not look like one piece.
• Not every part needs sealing. Parts with three or four good layers of paint and the sheen you want can stay as they are.
• Dust first. A speck under sealer is there for good.
• Seal stencils and lettering to bring them into one surface with the paint around them.
• Seal metallics, after they cure. Chrome rubs off even when it looks dry. Two days in the air, or ten hours in the dehydrator, then gloss. It loses a little of the chrome and reads more like metal.

Applying it. With Kaleido I use a 0.5 needle at 20 psi and lay a fairly heavy coat, creases first, without letting it pool. Thicker sealers may need a 0.7 needle, 40 to 50 psi and a flow improver. Sealer dries fast in the airbrush, so clean it between parts if it starts to spit. Then the dehydrator, one to two hours between layers, and a night before assembly.

Spray cans are very good and easy, but they want the outdoors or a big booth, and they care about temperature. Cold sealer gives an orange-peel surface: stand the can in warm water first. In the heat it dries before it lands and the surface goes sandy: keep out of the sun and spray closer.

Test every new sealer on spoons with all the paints you use: gloss, mask it, matt next to it, scratch it with a nail. Buy a small bottle first. You will not change all your paints to suit a sealer.

The course covers this whole stretch over five modules, from the primer to the sealer, with every brand, pressure and ratio on screen: the post-processing course

Assembly, last

https://www.youtube.com/watch?v=D8INoogYNFI

Real laces and strings. I stopped sculpting and painting laces after about twenty five pieces. Pick a thread by its texture at the figure's scale: a tight one for shoe laces, a soft scruffy one for a hoodie cord. Buy white and airbrush it any colour; it stays soft. Burn the tip with a lighter so it threads, and hold the ends inside with hot glue. A slice of heat-shrink sleeve on each end of a cord, shrunk with a heat gun rather than a flame, makes it look finished.

Two glues.

• Two-part epoxy with a five minute working time, not one or two. You can slide the part into place, it wipes off with warm water before it sets, and once set it is rubbery, so a part can come off again without wrecking the paint. Large parts, and anything that needs nudging into place.
• Superglue for small parts: one drop and it holds. But it cannot be moved, it shatters the part if you try to take it off, and a run of it ruins the paint for good. Check your gloves before you touch the figure.
• Hot glue holds better than people think, and two-part epoxy putty fills big gaps and carries weight.

A little glue goes a long way, in a few spots, not one big one. Build from the feet up, so the figure stands while you work. Try every part in place two or three times before any glue. Resin can warp after curing; epoxy lets you press a part into place, superglue does not. Glue shine that does escape disappears under a touch of matt sealer.

Put a handle in the sculpt. A few minutes in ZBrush adding a peg to hold each part while you paint saves cutting hot glue off a finished piece.

Mistakes that cost the finish

1. Piling paint on a first layer because it looks bad. It runs, and you strip it.
2. Painting over a speck of dust. It is there for good.
3. A coat on a part still warm from the dehydrator. It cracks.
4. Masking paint that is not dry, or leaving the tape on for hours.
5. A masked part in the dehydrator.
6. Running out of a mixed colour halfway through a figure.

Safety

A mask when you airbrush, even with a booth. Metallics, Alclad above all, only in a ventilated booth with a mask on. Gloves when handling primed and painted parts. Spray-can sealer outdoors or in a large booth.

Questions people ask

What primer should I use on resin 3D prints? A filler primer, Mr. Surfacer 500, sanded back, then a fine one, Mr. Surfacer 1,000 to 1,500. Grey for most colours, black under dark ones, white under bright ones.

What paint works on resin 3D prints? Any model paint that works over your primer. I use Tamiya acrylics thinned with Mr. Color Leveling Thinner for the airbrush, and Vallejo for the brush.

How many coats of paint? It depends on the colour and what is under it. Dark colours two or three thin layers, red three or four, yellow and white up to six.

Should I seal a painted 3D print? Yes, for anything that will be handled. The sealer protects the paint and sets the finish: gloss for eyes and anything wet, matt for cloth, a satin in between.

Superglue or epoxy for resin figures? Epoxy with a five minute working time for large parts and anything you need to adjust; superglue for small parts, sparingly.

How long between coats? An hour for a first layer in a dehydrator at 45°C, longer for each layer after. Let the part cool before the next coat. Then 48 hours before masking, decals or sealer.

Do I need an airbrush? For even colour on a figure, yes, it is the tool. A trigger airbrush with a 0.5 needle is the easiest place to start. Details can still be done with a brush.

Why does my red look pink? It is the first layer, or it is on a white primer. Give it the second and third layers, or prime in grey or black.

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A painted figure is the last stretch of a job that started with the print settings. Prime it properly, keep every layer thin, and give the paint the time it asks for. If you want the whole workflow in one place, from cleaning and curing through airbrushing and sealing to packaging, that is what the post-processing course is for: the post-processing course

Oasim / Karmieh Designer Toys