When people hear the word bleed in printing, they often think that it must be a problem. After all, when we think of colours bleeding in fabrics or people who are bleeding, that is usually not a good thing.
In fact bleed is the solution to a problem that can occur when sheets are cut to size after printing.
If a sheet is printed at the finished size, then bleed doesn’t come into the picture at all. But that’s not usually the case. Usually a printer prints a large sheet with several copies of the design repeated in a grid – say 4×4 or 5×3. And then the big sheet is cut down into several smaller finished sheets.
And that’s when bleed in printing comes into the picture. It is the way to make sure that when a large sheet is printed and cut into smaller sheets that there are no ugly strips of colour down the side of the print or bits of the design cut off and missing.
Take the example of a leaflet that will be A4 when it is cut to size and ready for the customer.
(A4 is the size of a sheet of UK copy paper.)
It is very unlikely that the printer will print the leaflets on A4 paper. It is much more likely that the printer will print the design on a much larger sheet with the design repeated several times.
Then, after printing, the printer will cut the large sheet to the finished size. That way the printer will get several leaflets out of one sheet, which is more efficient because it doesn’t need so many passes of the printing plate to get the required number of finished sheets.
The printer will lay out the leaflet design in a grid arrangement with the design repeated a number of times. Then, at each pass he will print eight, sixteen, or whatever number of leaflet designs will fit on the large sheet.
After all the big sheets are printed, he stacks them and cuts them with a guillotine to the finished size.
And that’s where the problem can start, because the guillotine may not cut exactly on the line where it is supposed to cut. A guillotine is a mechanical machine and not matter how well it is set up, it may cut just a fraction out from where it is supposed to cut.
And that is where bleed comes in as a way to deal with the problem of inaccurate cuts.
Bleed In Printing: Will It Show
The big question is what will show on the finished A4 sheet if the guillotine cuts a fraction out from where it is supposed to cut?
If the leaflet is designed with a white background and printed on white paper, then there won’t be any colour difference between the paper and the background colour.
But if the leaflet is the designed with a coloured background and the cut is slightly off, then there are two possibilities.
If The Guillotine Cuts Too Far Out
One possibility is that the cut will be too far out and in that case the white paper beyond the edge of the design will show.
It will show as a thin white line on the edge of the design where there isn’t any coloured printing ink on the paper. And it could be on one edge, or two, or three, or all the way around – and it usually looks bad.
Imagine a bright red poster with a thin white line along the top and down one side. It looks like what it is – a mistake.
If The Guillotine Cuts Into The Design
The other possibility is that the guillotine will cut into the design. If that happens, then maybe nothing wrong will show in the finished leaflet.
It depends on what’s near the edge. If it’s just a solid colour then it will look OK. If an important part of the design is right at the edge, a bit will be cut off and that may look bad.
If text near the edge and some of it is cut off, it will look bad. If it’s a photo of a person and the guillotine cuts off part of the person’s eye, it will look bad.
On the other hand, if it’s a person’s shoulder that’s near the edge of the design, it wouldn’t matter whether a bit less or a bit more of their shoulder was cut off or how much shows in the finished leaflet.
Let It Bleed
That is where bleed in printing comes in. Printers typically suggest 3mm either side of the intended extent of the finished product. In our example that is 3mm greater than the finished A4 sheet.
So the designer works on an area 3mm bigger all around than the size of the finished design.
So for an A4 sheet, which is 297x210mm, they will work on an area that is 303x216mm
That means that any background colour will overlap or bleed beyond the finished size and into that extra area.
So if the guillotine cuts a fraction out to one side, the background will still be the same colour as the rest of the design and there won’t be a white strip showing, and the leaflet won’t look cheap.
And if the guillotine cuts too far into the design, it won’t cut into a significant part of the design.
That said, it is still a good idea to keep important parts of the design away from the edge unless there is a good ‘design’ reason for doing so.