Some paint by number kits are printed on cardboard or canvas board rather than stretched canvas. They work perfectly well, they cost less, and they behave differently in two specific ways: they warp when they get wet, and you cannot stretch them onto a frame afterward.
Knowing that before you start saves the two problems people actually run into.
What you are actually painting on
Kits come on one of three surfaces, and they are often described loosely enough that you cannot tell which you are buying.
- Stretched canvas — fabric already mounted on a wooden frame, ready to hang when you finish. The most expensive and the least trouble.
- Rolled canvas — the same fabric, shipped flat in a tube. Cheaper, and you decide how to mount or frame it later.
- Cardboard or canvas board — a rigid panel. Canvas board is fabric bonded to card; plain cardboard or paperboard is printed directly. Cheapest, rigid, and the one people mean by "paint by number on cardboard."
Ledgebay kits are printed on pre-primed cotton canvas rather than board, so this is not a description of our own kits. It is what to expect if you have bought one that is.
The warping problem, and how to avoid it
This is the one thing that genuinely goes wrong with board.
Cardboard is made of paper fibers. Water-based paint puts moisture into those fibers, they swell, and as they dry they contract unevenly — so the panel bows, usually toward the painted side. Thin, plain cardboard is worst. Proper canvas board is much more stable but not immune.
What actually helps:
- Use less water. Paint straight from the pot wherever you can. Thinned paint puts far more moisture into the board than thick paint does.
- Do not soak it. Blot a wet brush before loading it.
- Work in sections and let them dry rather than covering the whole surface at once.
- Press it flat while it dries. Face up on a flat surface, weighted at the corners, overnight. This is the fix for a board that has already bowed slightly.
- Seal the back if you are being thorough. A thin coat of matte medium or gesso on the reverse balances the tension from the painted side. Do this before you start, not after.
A badly bowed panel can sometimes be persuaded flat with weight and time, but a severe curve is permanent. Prevention is the whole game.
What you cannot do with it
You cannot stretch a board over stretcher bars — there is no fabric margin and the substrate is rigid. If your plan for the finished piece is stretching it yourself, board is the wrong choice and rolled canvas is what you want.
You also cannot easily correct a deep gouge or crease in cardboard the way you can smooth out canvas. Treat the surface as slightly more fragile than it looks.
How to paint it
Same as any numbered kit, with one adjustment for moisture.
- Set up somewhere flat and well lit. A lamp pulled close does more for reading the numbers than anything else.
- Stir each pot before use. Pigment settles.
- Work dark to light. Dark colors cover the printed numbers in one coat, so the panel tidies up early and you can see the picture emerging. Pale colors often need two coats, and light paint straying into a dark area is easy to cover afterward. The reverse is not true — and you will find plenty of guides telling you to start light, which is the single most common piece of bad advice in this hobby.
- Keep the paint fairly thick. On board this matters more than on canvas, because thinned paint means water in the substrate.
- Let each area dry before working next to it. Acrylic sets quickly, so this is rarely a long wait.
- Rinse and blot your brush between colors. Blotting is the step people skip, and on cardboard it is the one that keeps the panel flat.
A trick worth knowing on any kit: shading a printed number with a white colored pencil before painting a pale color over it lets that color cover in one coat instead of three.
Finishing and framing
Let it cure properly before doing anything to it — touch-dry is not cured, and acrylic keeps hardening for days.
Board is genuinely easy to frame. It is rigid and a standard size, so it drops into an off-the-shelf frame without mounting, backing or stretching. That is the real advantage over rolled canvas, which needs work before it can go on a wall.
A coat of varnish once cured protects the surface and evens out the patchy sheen you get where some colors dried matte and others satin. On cardboard, use a spray varnish rather than a brush-on if you can — less moisture.
Is board or canvas better?
Board if you want the lowest price, a rigid surface that will not need mounting, and something that slots straight into a frame.
Canvas if you want the finished piece to look and feel like a painting rather than a printed panel, or if you want it pre-stretched and ready to hang with no further work.
The honest difference is in how it reads when finished. Canvas has a weave that catches light and looks like a painting from across a room. A flat board looks flatter. Whether that matters depends entirely on what you want at the end.
Our kits are on pre-primed cotton canvas, rolled in a tube rather than folded, in a range of designs — and there is a custom option printed from your own photograph. If you would rather see how finished ones look before deciding, the customer gallery is all real work sent in by the people who painted it.
For more on the surface question generally, we compared rolled canvas against pre-stretched separately.
