The greater the number of folds that are used, the greater the variation in position (Register). To demonstrate this principle, carefully fold by hand a reasonable sized sheet of paper four times, each time fold the longest side in half (32 pages) and see the variation at the foot. Take this variation into consideration when designing a folded leaflet or book section ; the thicker it is the more variation there is.
If a design has to run across a pair of pages, try to use a ‘natural pair’ i.e. the centre of a folded section, rather than hope that an exact fit will happen when folding.
For double or open gatefolded leaflets, allow the design to finish short in the centre, leaving a paper gap of 3mm to 15mm.
If the flap forms part of the book as a cover ensure that the flap can be opened out to view once the inside sections are inserted.
On concertina or roll fold leaflets, because of the potential variation in folding, avoid making every other page a solid e.g. one page complete solid, one page white with text and so on.
For work with multiple folds, take care that it does not become too thick or too small for the folder. As a guide the normal maximum thickness a fold unit will take is 2mm – this will give a final thickness of 4mm, so keep well under that.
Printers print using new, flat sheets of paper. After several times through the press it finds its way on to a folder. It’s not surprising it does not have that flat pristine look it once had, yet the same expectations are there.
For multiple fold work choose a paper that is resistant to cracking. The grain should be parallel to the fold for paper below 115g/m2, above that, scoring or creasing will be necessary.
If the design has solids that bleed, and they are near the edge of the printed sheet, allow more paper as this can avoid problems with the edges of the sheet curling, causing spoilage and delays.
Perfect Binding sections that have to be folded, should be perforated down the spine to release trapped air. Avoid using a large toothed perforator that makes the section difficult to feed later on through a collator (spine first).
If a concertina leaflet is required allow more bleed on the foredge side of the cover page, as this will need to be slightly wider to cover the folded leaves behind it.
It is also good advice for most leaflets to allow greater bleeds on the front page.
Side lay marks should be clearly indicated for the finisher; and as the printer often uses several side lay marks guess-work would lead to confusion and poor quality work.
A5 work and tumble work must have the paper cut accurately; allow a trim out between copies, never a single cut.
Work that is laminated or varnished both sides may be difficult to fold, although varnish applied on the 5th unit of a printing machine is usually suitable for folding.
Below 60 g/m2, folding is possible, but a higher degree of skill is required and spoilage is much greater. If edge trimming is going to be used, 10mm should be allowed.
2-up & 3-up Printing:
If it is possible to fold the job 2-up, then lay the plates down so they are both in the same position one way and head to foot the other way.
Allow for a single cut between copies if there are no bleeds. With bleeds try to make the solids meet and allow 6mm trim out between the copies. Work done 3-up is possible but the centre copy will be rotary slit top and bottom and this may be unacceptable, especially so on thicker paper or with multiple folds.