How to Get Fold Lines Out of a Large Paint by Numbers Canvas

You opened a big canvas and there's a fold line running across it. It looks bad. It isn't. That line will come out, and you don't need anything you can't find at home.

It's the message we get most often from people who've just opened a large canvas, so you're in good company. Here's the short version: damp the back, tape it flat, leave it overnight. The rest of this page is for the fold that needs a little more persuading.

One thing worth knowing before you start. A fold line is a sharp crease with a definite edge, made when the canvas was folded flat. A roll curl is the soft bend you get from a canvas that traveled in a tube. They look similar in the box, but the fold is the one that needs work. A curl usually drops out on its own within a day of lying flat.

Why did my canvas arrive folded?

Big canvases normally travel rolled up in a tube. On some delivery routes a tube that long can't be carried safely, so we fold the canvas instead.

It's the better of two options. A folded canvas flattens out again in a day. A tube that gets crushed in transit does real damage, and that can't be undone. So when you see a fold line, you're looking at a canvas that arrived in one piece.

Three rules before you start

• Work on the back, never the front. The printed numbers and outlines are on the face of the canvas, and heat or hard rubbing can lift them.
• If the parcel has been sitting somewhere cold, bring it inside and give it a few hours. A cold canvas is stiff, and stiff canvas holds onto creases.
• Don't start painting until it's flat. Paint sits on top of the fabric and copies its shape, so a ridge you paint over is still a ridge afterwards.

The fix: damp the back and tape it flat

This is the one that works on a large canvas. You'll need a spray bottle of water, a clear table or a board bigger than the canvas, and some tape.

1. Lay the canvas face down, so you're looking at the blank back.
2. Mist the back lightly with water. You want it damp all over, not wet. No puddles.
3. Smooth it out with your hands, working from the middle toward the edges.
4. Tape all four edges down to the table. Pull each side gently taut as you go, and use a low-tack tape such as our artist masking tape so it lifts off cleanly afterwards.
5. Leave it overnight. Take the tape off in the morning.

Damp canvas relaxes. Drying while it's held flat is what makes it stay flat, so the tape is doing the real work here.

What we see in practice: the crease is usually gone by morning. A faint line can linger for an hour or two after the tape comes off. Give it that time before you judge it. If it's still there by lunchtime, it's a stubborn one, and the next section is for you.

You may have read that you should pile heavy books on it. That works on a small canvas. On a big one you'd need books across the whole surface, and books only press down. Tape pulls outwards, which is what actually takes a crease out.

Can I just iron it?

You can, on the back, on a low setting with the steam off, with a cloth in between. But there's a catch on a large canvas that nobody warns you about.

Your ironing board is shorter than the fold. If you press it in sections, each finished section tightens up slightly against the one you haven't done yet. You end up with a gentle ripple across the canvas instead of a single crease.

So use a table rather than the board, and overlap each pass generously so no part gets pressed twice as much as its neighbor. For the basic technique, we've written it all out in our step-by-step guide to flattening a canvas.

Still see the line?

A few folds are stubborn. Here's what's left, and one thing to get right about the frame.

The first is gesso. Gesso is the white primer artists brush onto bare canvas before painting, and you can buy a small pot at any art shop. Painters use it on a fold that won't shift. Brush one thin coat across the back of the canvas and let it dry flat. As it dries it tightens the weave and pulls the line out with it. Do this before any framing, because it stiffens the canvas and makes stretching harder later.

Now the frame, and this is the part people get backwards. Deal with the fold line first, then assemble. Our DIY wooden frame pins the canvas in place, it does not haul it tight over bars. That keeps a flat canvas flat. It will not pull a fold out of one that is still creased.

There is a practical reason to do it in that order too. Once the canvas is pinned to the frame you cannot lay it face down, iron the back, or tape it to a table. Every fix on this page needs a loose canvas. So get the line out, let it dry, then mount it. Large canvases currently come either rolled or with the DIY frame rather than ready-stretched, and we've explained the difference in rolled or stretched canvas.

Will the fold show in the finished painting?

If the line has gone flat, no. Once there's paint over it you won't find it again.

If there's still a ridge standing up, yes, it will show. That's worth knowing before you start rather than after.

There's an easy way to check. Tilt the canvas so a lamp catches it at a low angle, almost side on. A ridge casts a small shadow along its length. A crease that has settled flat casts nothing. Straight-on light hides both, which is why a canvas can look fine on the table and show a line later on the wall.

Next time you order a large canvas

Add the frame to the same order so it's waiting when the canvas is ready. Flatten first, mount second, and it's one afternoon's job. Large canvases are worth the extra effort. Sweeping landscape paint by numbers scenes need the room to breathe. Photos are the other favorite at this size, which is where large custom paint by numbers comes in.