The crack down the middle of your fold

A heavy cover has returned from a job, and a white line is running down the fold. The printed color has split open, and the paper underneath is showing through. Nothing was done incorrectly at the press. The sheet was folded without being scored first, and thick paper does not forgive that.

Scoring is a production step that often goes unnoticed until it's omitted. It is a cost-effective process that requires minimal time. However, neglecting it can lead to a significant portion of finishing complaints in commercial print. This is what scoring does and when it is necessary.

What actually happens when paper folds

Paper consists of compressed fiber layers. When folding a sheet, the fibers on the inside of the fold compress, while those on the outside stretch. Thin paper handles this process easily due to its minimal material and the small difference between the inside and outside layers.

Thickening the sheet alters its geometry, making it work against you. The outer layer of the fold now has a significantly longer distance to travel compared to the inner layer. Beyond a certain thickness, the fibers cannot stretch that far, causing them to tear. What appears as cracking is actually the fibers failing under tension.

Coated stock makes the issue worse and more noticeable. The coating, which is a mineral layer on the surface, has very little ability to stretch. It cracks before the paper fibers do, and because it is white underneath a dark ink, the crack becomes very apparent.

Why dark colours show it most

A cracked fold on a white sheet is nearly invisible. The same crack through a black cover appears as a bright white line. This is why the issue seems to affect precisely the types of jobs where it matters most: jobs involving heavy stock, dark solid coverage, and important covers. The physics of the problem is the same on a pale sheet, but you simply cannot see it.

Scoring and creasing

The solution is to prepare the fold before actually making it. A rule is used to press a channel into the sheet along the fold line. This process compresses the fibers in a controlled manner, giving the paper a hinge. When the sheet is then folded, it bends along that channel instead of tearing across an arbitrary line.

The terms are often used interchangeably, but there is a distinct difference. Scoring typically involves pressing a line into the sheet. Creasing, on the other hand, usually involves forming a channel with a matched rule and counter, causing the paper to be pushed into a groove rather than simply being squashed. Creasing results in a cleaner finish, especially on heavy or coated stock, which is why it is standard practice for quality cover work.

Which way the fold goes matters

A scored sheet should fold with the channel on the inside of the bend and the raised bead on the outside. Folding it the opposite way would exacerbate the issue rather than resolve it, as the compressed channel would then be on the stretching side.

This detail seems like something for the bindery. It affects the customer in one specific scenario: a piece with folds going in both directions, similar to a concertina. In this case, some folds crease one way, while others crease the other way. The artwork needs to be marked clearly to avoid confusion. When dealing with a job like this, always send a folding diagram.

When you need it

The laminated row is worth pausing over. Lamination is often assumed to protect a fold, but it changes the failure rather than preventing it. The film itself does not crack, so the surface can look intact while the paper underneath has separated. You end up with a fold that feels soft and hinged, but is structurally broken. Scoring before folding remains necessary.

The grain direction question again

Paper fibers generally align in one direction, determined when the sheet was formed. Folding along the grain is easier because you are separating fibers that already run parallel to your fold. In contrast, folding across the grain is more difficult because it requires breaking fibers, causing the paper to crack more readily.

Where possible, folds should run with the grain. This decision is made during the job layout on the sheet and can sometimes conflict with maximizing the number of pieces per sheet. This presents a genuine trade-off between cost and quality. In cases involving heavy cover stock with dark folds, quality should take precedence.

You do not need to specify this. You do need to know it exists, because it explains why a printer might ask to change how a job sits on the sheet, or why a slightly different finished size sometimes costs less. The related decisions at large sizes are covered in our guide to preparing large format artwork.

Perforation, the same idea for tearing

Perforation is akin to scoring, but instead of preparing paper for folding, it prepares paper for tearing. This involves creating a line of small cuts, with uncrushed paper between them. Consequently, a section can be cleanly separated when pulled.

The variable is the ratio of cut to gap. If there's more cut, it tears easily and may also tear in the envelope during transit. Conversely, if there's less cut, it survives transit but someone has to struggle to separate it.

• Reply cards posted in bulk should have a conservative perforation.
• Tear-offs on a counter can be looser, as nothing will jostle them.
• Anything perforated near an edge weakens the sheet, making it more prone to damage during handling.
• Perforation across a heavy stock still benefits from a score line alongside it.

Ask before you approve, not after

We routinely score any item that requires it. We prefer to address the scoring at the quotation stage rather than explaining a cracked cover afterward. If your job involves a heavy cover with dark coverage across the spine, it's essential to confirm that scoring is included in the specifications.

Two things you can do to genuinely help. First, clearly indicate which way each fold goes if there are multiple folds. Second, when deciding between a 250 gsm coated cover and a slightly lighter uncoated one, ask about the appearance of each option at the fold before making your decision, not after receiving the proof.

You can see the range under general printing services, and our note on banner finishing covers the equivalent decisions on large format work. If you have a folded piece coming up, send the artwork through the contact page and ask what the fold will do. A cracked cover is a problem nobody can fix once the sheets are folded.