When you print folded leaflets, you'll sometimes see a white line — or even visible cracking — running along the fold. It usually comes down to the paper's thickness and quality. Here's what causes those white edges, and how to keep them off your job.
What paper can be folded?
Whether paper shows a white edge when folded depends on the sheet itself — its grain direction (the way the fibres run), its thickness, and its printed colour. Thickness matters most. Stocks of 128 gsm, 157 gsm or lighter can be folded the normal way: the sheet is thin, soft and springy, so machine folding won't press hard enough to break the fibres. Stock heavier than 157 gsm has tighter fibres, so the machine has to apply more pressure to fold it — and that can crack it.
Beyond weight and thickness, grain direction also affects how a fold finishes. When the fold runs with the grain, it's less likely to split the fibres — but that's more of a theoretical ideal. Gang-run printing packs every sheet as full as possible, so the factory doesn't control grain direction.
If the paper you're folding is printed mostly in dark colours, the white edge stands out more and looks unattractive, as in the image below. Thinner paper can also take more folds than thick paper — in other words, the thicker the paper, the easier it is to crack the fibres.
(Because the machine folds under heavy pressure, white edges form easily.)
How to avoid cracking along the fold:
1. Use a lighter-weight stock. Thick paper has denser fibres, so it cracks more easily.
2. Score before folding. Scoring first, then folding is not only easier — it prevents white edges. Scoring uses a machine to press a groove into the surface of the sheet before it's folded, which reduces splitting. It does help avoid white edges, but bear in mind that both scoring and folding still stress the fibres and cause some wear.
3. Laminate before folding. Lamination protects the sheet because the film is elastic, adding toughness at the fold. Whether the job is scored or simply folded, there's far less risk of the paper cracking and showing white edges.
Planning a folded leaflet and not sure which stock or finish will fold cleanly? We deliver across Hong Kong and Macau, and you're welcome to WhatsApp us at +852 3001 5678 (English is fine) to talk it through before you print.