You painted a section yesterday, and this morning the dried color is dotted with tiny craters and a few popped bubbles. Pinholes and bubbles in dried paint by numbers look like the surface breathed and got stuck that way.
In short, those pinholes are trapped air. Specifically, shaking the pot, paint that's too thick, scrubbing the brush back and forth, or a slick, hand-oiled canvas all whip air into the film. Acrylic dries fast, so bubbles get locked in and pop, leaving little holes. Importantly, it's fixable and preventable, not a defective kit. Below is a quick cause-to-fix diagnostic for your paint by numbers kit, plus how to repair spots that already dried rough.
Key Takeaways
- Pinholes and bubbles are trapped air in a fast-drying acrylic film, not a bad kit. The film skins over before the air can escape and level out.
- Shaking the pot is the most avoidable cause. Golden's lab found that gentle hand-stirring whips in far less foam than shaking, and that trapped foam weakens the dried film (Just Paint, Golden Artist Colors' technical publication).
- Three habits prevent almost all of it: stir don't shake, thin to a smooth self-leveling flow, and stroke in one direction instead of scrubbing.
- For pinholes that already dried, let the layer cure, sand the spot lightly, and recoat thin. That follows the manufacturer-standard dry-then-sand-then-repaint sequence (Sherwin-Williams).
Why does dried paint by numbers get tiny holes and bubbles?
First, some quick definitions. Pinholes are the tiny concave craters left behind when an air bubble pops in a setting paint film. Cratering is the broader term for those dimpled, uneven patches across a coat. Both share one cause: air gets locked into the paint before it can escape.
Here's the mechanism in plain terms. Acrylic dries from the top down, so a skin forms on the surface fast. As a result, any air whipped into the paint, or driven in as you apply it, gets sealed underneath that skin. The film can't level out in time, because it's already setting up. Subsequently, those trapped bubbles work their way upward and pop, and each one leaves the little concave crater you're seeing in the dried color. It's a timing problem more than a material one: the air simply runs out of room before the paint is ready to let it go. That's also why the same pot can paint smooth one day and pitted the next. The difference is how much air you put in and how fast the film closed over it. It's not the quality of the paint itself.
The mechanics aren't unique to art paint. For example, Sherwin-Williams notes that shaking and too-rapid brushing drive air into the film. Fast drying then seals it before it can level out, producing bubbling, pinholes, and cratering (Sherwin-Williams). The same physics applies to the small acrylic pots in your kit. In fact, from our work with thousands of painters, those four causes account for nearly every pitted finish we see. Here's how each one maps to its symptom and fix.
| Cause | What it does | Fix |
|---|---|---|
| Shaken or vigorously stirred pot | Whips micro-air bubbles through the paint | Fold it gently with the brush tip; let it rest a minute |
| Paint too thick or gummy | Air can't rise out before the skin sets | Thin a touch to a smooth, creamy flow |
| Aggressive back-and-forth scrubbing | Drives fresh air down into the wet film | Stroke smoothly in one direction |
| Unprimed or hand-oiled canvas | Paint beads and crawls instead of wetting out | Wipe oils off; thin-prime a slick spot if needed |
Notice the pattern. Most pinholes trace back to either air going in, or the film setting before the air can get out. Accordingly, fix those two things and the craters largely disappear.
How do I mix without whipping in air?
This is the single highest-leverage habit, so it goes first. The instinct is to shake a pot like salad dressing or stir it hard to loosen it up. However, both load the paint with tiny bubbles you can't see, and acrylic seals them in before they can rise out.
Golden's lab is explicit on this. Specifically, a gentle stir foams far less than shaking. That trapped foam doesn't just cause surface pinholes. It weakens the dried film itself (Just Paint, Golden Artist Colors' technical publication). Therefore, treat the pot gently.
In our experience, the simplest routine works best. Pop the lid, then fold the paint slowly with the brush tip or a toothpick: think turning, not beating. Then let the pot rest for a minute so any bubbles you did make can rise to the top and break. Notably, that one-minute pause does a surprising amount of work for free.
Is my paint too thick? Thinning to a smooth flow
Thick, gummy paint is a bubble trap. It holds onto air, drags under the brush, and won't self-level, so every imperfection sets exactly where you left it. In contrast, a smooth, creamy flow settles flat on its own. That's the target, not a watery wash that won't cover the numbers.
A few drops of water often does it. A flow improver is a clear additive that loosens paint and helps it level without watering down the color or weakening coverage. For instance, a pot can go thick or gummy from sitting open too long. A flow improver like our Flow Aid paint reviver brings it back to a smooth, workable consistency without thinning the color down to nothing. Consequently, that gummy-pot revival fixes a common bubble cause right at the source, because workable paint releases its trapped air instead of holding onto it. In our experience, a thick or half-dried pot is behind a surprising share of the pinhole complaints we get from painters. A quick revive solves it before the brush ever touches the canvas.
We keep the exact ratios and the "don't drown it" rule in our guide on whether to use water with paint by numbers. In particular, the rule for bubbles is simple: thin just enough that the paint levels, not so much that you need three passes to cover.
How should I move the brush?
Two prevention levers live here: how you stroke, and what you stroke onto. Both decide whether air gets driven into the film or stays out of it.
Stroke in one direction
Scrubbing the brush back and forth pushes fresh air down into the wet paint with every pass. In contrast, smooth strokes that go one way, then lift, leave the film alone. As a result, reload the brush rather than reworking a patch that's already starting to set. Similarly, a good small brush helps the paint lay flatter; we cover a few in our roundup of top brushes and tool upgrades.
Start on a clean surface
Microscopic hand oils make a slick spot where paint beads up and craters instead of wetting out. Therefore, wipe the canvas with a clean, dry cloth before you start, and keep your fingers off the areas you haven't painted. Specifically, if one patch stays slick and won't take paint evenly, a whisper-thin coat of gesso gives it enough tooth to grip. For pulling the whole finish together, this pairs with our guide on getting professional results.
How do I fix pinholes that already dried?
This is the repair most painters actually need, and it's the one customers write in about most. The good news: rough, pitted spots sand out and recoat cleanly. As a result, you don't have to live with them.
Work in order, and don't rush the first step. First, let the layer cure fully. Give it several hours, or overnight if you can, so it's genuinely hard, not just dry to the touch. Then sand the rough spot very lightly with fine grit. Use a feather-light touch so you knock down the raised edges of the craters without digging through the color underneath. Subsequently, dust off the grit with a soft, dry brush and recoat thinly. The thin recoat matters: a heavy one just traps fresh air and pits all over again, undoing the work you just did. In fact, that dry-then-sand-then-repaint sequence is the manufacturer standard for bubbling, pinholes, and cratering. It's the same approach the pros use on full-size work (Sherwin-Williams).
One caveat: this is a surface-texture fix. In contrast, smudges, slips, and color bleeding over a line are a different repair entirely. We walk through those in our guide on how to fix mistakes like a pro. For craters and pinholes, though, sand and recoat is the move.
Prevention checklist for a smooth coat every time
Most of this comes down to slowing down at two moments: when you mix, and when you stroke. Here's the whole routine in one place.
- Stir gently with the brush tip or a toothpick, never shake, and rest the pot a minute.
- Thin to a smooth, creamy flow that levels on its own, not a watery wash.
- Wipe hand oils off the canvas, and thin-prime any slick spot that won't take paint.
- Stroke in one direction instead of scrubbing back and forth.
- Lay thin, even coats and let each layer dry before recoating.
Additionally, a clean, well-shaped brush makes smooth lay-down easier. The right brushes and accessories do a lot of the work for you on a tricky surface.
How we make a smooth coat easier
We've tuned our kits around this exact problem. Specifically, our high-opacity paint covers in fewer, thinner passes, so there's less temptation to glob it on, and less paint means less trapped air. Similarly, our wrinkle-free canvas gives you a flat, even surface to work on instead of fighting ridges that pool paint.
And if a pot ever arrives gummy or dried out, our 30-day money-back guarantee has you covered. Good materials won't replace a gentle stir and a single-direction stroke. Nevertheless, they tilt the odds toward a smooth coat every time. You can read more about us and how we build every kit on our about page.
Reviewed by the Davincified editorial team. Got a pinhole or bubble situation we didn't cover? Contact us. In our experience every canvas is a little different, and we keep this guide updated as new fixes come in from painters.
Frequently Asked Questions
Usually it's how that pot was handled, not a defect. For instance, a color you shook or stirred hard, or one that's gone thick from sitting open, traps more air than the others. Therefore, stir it gently, thin it to a smooth flow, and rest it a minute, and that color should lay as flat as the rest.
Almost certainly not. In fact, pinholes and bubbles are trapped air in a fast-drying acrylic film, and the same thing happens to professional house and artist paints (Sherwin-Williams). They come from mixing and brushing habits, which you control. However, if a pot truly arrives dried out, our guarantee covers a replacement.
Recoating over a rough, pitted spot tends to keep the texture, so the craters still show through. In contrast, letting the layer cure, sanding the spot lightly with fine grit, dusting it off, then recoating thinly works far better. As a result, the surface is smooth first, so the new coat lays flat instead of following the holes.
Give it several hours so the film is genuinely hard, not just dry to the touch. Otherwise, sanding too early gums up the grit and tears the soft paint. However, once it's firm, a light pass with fine sandpaper knocks down the high points, and you can dust and recoat the same day.
Not if you thin gently. Specifically, the goal is a smooth, creamy flow that levels on its own, not a watery wash. For instance, a few drops of water or a flow improver keeps the paint opaque while letting air escape. However, if you need three passes to cover the numbers, you've thinned too far, so pull back.
Usually no. The canvas comes ready to paint. Specifically, priming only helps in one case: a slick spot, often from hand oils, where paint beads up and craters instead of wetting out. In that case, a whisper-thin gesso coat gives the surface enough tooth to grip. Nevertheless, wiping oils off first solves most slick-spot problems on its own.
