Source:
Heidelberg: Folding Techniques. (There's no more bibliographical information on this publication.)
TIMELINE
- How is mechanical folding done?
- Telescoping: Create a 1/3 page in InDesign
- Grain Direction Tests
- Folding Lingo
- Types of Folds
- Imposition Exercise
- InDesign InBooklet Exercise
Folding
What is folding?
Folding involves the use of a tool or mechanical pressure to produce a sharply defined fold. The pressure required for folding may be applied manually with the use of a bone folder, however, I will only address the mechanical aspects of folding for production.
In mechanical folding the sheet is doubled between rollers while pressure appropriate to the thickness of the paper is exerted. The end result is a sharp fold that virtually eliminates the paper's natural tendency to revert to its original shape.
Principles of Mechanical Folding
In the process of mechanical folding, there are two commonly used techniques—knife folding and buckle plate folding. One type of folding may be used alone or both techniques can be combined.
Knife Folding
Knife folding uses a vertically moving knife and two rollers rotating in opposite directions. The sheet is carried from the feed to the folding station until it makes contact with the sheet stop. At this point, the knife descends vertically, plunging the sheet between the rollers that have been set to the thickness of the sheet going through them. As the sheet passes through the rollers, it is pinched and the fold is formed. This folding process is dependent upon the repetitive action of the knife.
Only one folding knife is to be found in any one folding station. For every subsequent fold, it is necessary to have a further knife folding station at right angles to the preceding one. Printers and binders specializing in folding large sheets usually use knife folders.
Buckle Folding
A buckle folding station consists of three rollers and a buckle plate. The first two rollers are arranged vertically above one another and their job is to carry the incoming sheet into the buckle plate until it reaches an adjustable feed guide stop.
The sheet is delivered into the buckle plate at a speed determined by the characteristics of the paper. As the lead edge of the sheet strikes the feed guide stop, the sheet continues to be fed into the buckle plate, creating a buckle in the space between the three rollers. As the excess paper drives downwards it is grabbed by the rollers and the fold is formed as the sheet passes through them.
Unlike knife folding, buckle folding is not restricted to any cyclical movement, which makes it ideal for high-speed folding. Each folding station can fit up to six buckle plates, arranged alternately above and below each other, allowing for a large number of fold variations.
Grain Direction
The direction in which the web moves through the paper machine is said to be with the grain, whereas the direction across the web is said to be against the grain. With the grain, there is greater strength, and against the grain there is greater expansion and contraction which makes it less stable. This strength with the grain occurs because during the manufacturing process, the fibres are stretched so that they lose virtually all further capacity for expansion, which creates relatively good dimensional stability.
Depending on the quality of the paper, folded sheets retain a certain degree of resilience after folding so that they have a tendency to reopen. The angle of opening is least with parallel folds, and most noticeable with right angle folds.
A fold is cleaner and more resilient when the grain is parallel to the fold. A fold against the grain may not lay as flat, and can cause cracking most noticeable in areas of heavy ink coverage. A fold against the grain is less resilient, and the pressure exerted by the rollers must be somewhat less to avoid an excessive weakening of the paper along the fold line. If folding against the grain is a must, a die-score can alleviate some of these problems, as well as careful paper selection.
Testing the Paper Grain
The following tests can be used to determine grain direction:
Fingernail Test
With the fingernails of the thumb and middle finger, pinch and slide down the vertical and horizontal edges of the sheet of paper. With the grain, there is virtually no change but, against the grain, a wave will be clearly visible.
Bending Test
When a square test-sheet is bent in both directions, there will be less resistance parallel to the grain than against it.
Tearing Test
Tear a sheet on the vertical dimension, then tear it horizontally. With the grain, the tear will be relatively straight. Across the grain, there will be greater resistance to tearing, resulting in a jagged edge.
Narrow Web and Wide Web
A distinction is drawn between narrow web (NW) and wide web (WW) depending on the way in which the format is cut from the paper web.
When paper is being ordered it is essential to indicate either WW or NW after the format, underlining the stretch-side, e.g., 70 M/100 cm NW or 70/100 cm WW.
Narrow Web
The sheet is cut from the web (roll) with the grain; grain follows the narrow side of the sheet.
Wide Web
The sheet is cut from the web against the grain; grain follows the wide side of the sheet.
How Paper Affects Folding
Manufacturing Processes and Grain Direction
Paper fibres have certain characteristics that depend upon the nature of the composition of the fibre and the way in which it is milled. As climate changes, the fibres can expand and contract considerably in their thickness, but, in terms of length, they remain virtually unaltered. The way that paper fibres are laid down in sheets during manufacturing determines the grain direction.
Machine-Manufactured Paper
Paper produced by machinery—vat machines or long web machines—has a pronounced grain direction because the fibres align themselves parallel to the direction of movement on the machine.
Hand-Made Paper
The highly diluted pulp of a hand-made paper is evenly spread over a web through manual shaking which causes the fibres to follow a random orientation. For this reason, there is no discernible grain direction in hand-made paper, and the effects of expansion and contraction are virtually identical in both directions.
Understanding the Lingo
There are several common folding-related words or phrases, and understanding this lingo is crucial to learning about folding.
Flat Size vs. Finished Size
The flat size is the exact dimension of the printed piece when laid flat. This measurement should include all folding compensations, but should never include bleed allowances because bleed is pulled past the edge of the page in the digital document. Digital document page dimensions and flat size should always be the same measurement.
Finished size is the exact dimension of the printed piece when completely folded.
Why Compensation is Key
What looks like a folding mistake by the bindery is often designer error. Remember that if a panel is to fold into another, it must be slightly smaller or there will be what is called "telescoping", or the inability for the folded sheet to lie flat. It will have a roundish profile because the panels are too long and push against each other for lack of anywhere else to go. The bindery will adjust the panels so there is no telescoping, but margins and colour breaks will shift noticeably. Pay attention to the adjustments and apply them consistently for good, predictable results.
Panels vs. Pages
Panels are 2-sided sections of the printed piece, defined by the crease of the fold. A page is one side of a panel.
For example: The Accordion fold below is three panels, each of the three panels is 2-sided, and each side is considered a page. So, the three-panel Accordion has 6 pages. If we take that same fold and make it a Broadside Accordion instead, then it changes to 6 panels (although it's finished in a 3-panel Accordion format) and the page count rises to 12.
Panels vs. Flaps
Panels are 2-sided sections of the printed piece, defined by the crease of the fold. Flaps are shortened versions of panels, and can also be called short panels, since there is no official guideline as to when a panel becomes a flap. Below is a Letter Fold. Next to that is a Letter with Hidden Flap (there is also an Exposed Flap version of this fold). They're really the same folding style—the only difference is the width of the fold-in. Flaps are usually less than 1/2 the dimension of the finished width or height, depending upon the direction of the fold.
Pages vs. Spreads
A page is a one-sided section of a folded piece, defined by the crease of the fold. Spreads are 2 or more pages meant to be viewed as one. For example, in the Letter Fold, the cover is a page, the back cover is a page, but two or three of the inside pages are viewed at the same time when the piece is opened up, and therefore those pages together are considered a spread.
Parallel Folds vs. Right Angle Folds
The first fold of any folding style is always a parallel fold. The next fold can be a parallel fold or a right angle fold, depending upon the folding style.
Parallel folds are parallel to each other. Right angle folds combine with parallel folds to make right angles. So, a right angle fold cannot happen without a parallel fold.
Broadside vs. Short Fold
A broadside-style fold doubles its area by folding in half on itself before any characteristic folding style is created. For example, a Broadside Letter fold is 12 pages, whereas the Letter Fold is 6.
A short fold is a broadside fold, too. The only difference is that the broadside fold is a little less than twice the area because in a short fold the fold-over panels are shorter than the finished height.
Printer vs. Bindery
There are several types of printers—commercial printers, quick printers, publication printers, digital printers, packaging printers and more. Printers specialize in putting ink on a substrate (paper, or other, depending upon what type of printer they are). For convenience, most print shops have at least some in-house binding capabilities.
There are several types of binderies as well—commercial binderies, specialty binderies, publication binderies, and more. Binderies specialize in print finishing, which includes folding, binding books, brochures and periodicals, and often die-cutting, gluing, foil stamping, shrink-wrapping, wafer-sealing, auto-inserting, and other related finishing needs. Binderies can be very large or moderate in size, but they generally have more finishing equipment than the average print shop, which gives them more capacity, speed, and flexibility to manage longer run jobs and specialized projects.
Bindery vs. Specialty Bindery
As mentioned above, binderies can manage a multitude of finishing needs, but specialty binderies can handle the most challenging and creative bindery work. Some are normal binderies with some specialized capabilities, and some are capable of just about anything a designer can dream up. Certain specialty binderies can mechanize difficult folding styles—often "rigging" machinery to do extremely difficult work that might have normally been considered hand work. Some can handle miniature folding, large map folds, stringing tags, pop-ups and more.
So, how does one discern a specialty bindery from a regular bindery? It's not usually in their name—there are some well-known specialty binderies that can be found by word-of-mouth or on the Web. If all else fails, ask your favorite bindery—you may not know the breadth of their capabilities.
Mechanical Fold vs. Hand Fold
A mechanical fold is any fold that can be done by machine. Hand folds are folding styles that must be done completely or partially by hand. Often, due to limitations of equipment, a fold is taken as far as it can go by machine, and then the last fold or two is done by hand by a group of workers in the bindery. Some folding styles that are considered hand folds can be done by machine at speciality binderies.
Hand folding is very expensive, and requires a die-score and more time built into the finishing schedule.
Fold Names
- A—Accordion fold (commonly nicknamed zig-zag, z-fold, back-and-forth).
- D—Double parallel (indecision/ignorance often renders this fold nameless).
- R—Roll fold (commonly called a wrap, barrel fold, over-and-over).
- G—Gate fold. (This is not a double gate! It passes through the gate attachment once, and for that reason is called a gate fold.)
- L—Letter fold or six-page standard. (This is not a single gate! No gate fold attachment is required to make this folding style, thus it is not a gate fold. Other common nicknames are C-fold, tri-fold, leaflet.)
- E—Eight-page broadside or eight-page signature (often incorrectly called French fold).
- F—Four-page standard. (Single fold is the most common nickname for this one.)
Format Options
There are four basic formats: upright, oblong, narrow, and square. Certain measurement ratios, described below, will qualify a given folded piece as a specific format. It is important to note that not all folding styles can be built in all four formats.
Upright
To qualify as an upright format, the finished height of the folded piece must be more than 3/4 inch greater than the finished width. Some common upright dimensions are 5" x 8" or 4" x 6". An example of how to communicate format to the printer would be: "4-page Standard, upright format," followed by the finished dimensions.
Oblong
To qualify as an oblong format, the finished width of the piece must be more than 3/4 inch greater than the finished height. Some common oblong dimensions are 6" x 4" or 8" x 5". An example of how to communicate format to the printer would be: "4-page Standard, oblong format," followed by the finished dimensions.
There are special considerations for an oblong format piece—check with the printer or print finisher about the minimum height capabilities of the folding machinery.
Narrow
To qualify as a narrow format, the finished height must be at least twice the finished width. Some common narrow dimensions are 4" x 8" or 3" x 9". An example of how to communicate format to the printer would be: "4-page Standard, narrow format," followed by the finished dimensions. There are special considerations for an narrow format piece—check with the printer or print finisher about the minimum width capabilities of the folding machinery.
Square
To qualify as a square format, the difference between the finished height and finished width cannot be more than (+/-) 3/4 inch. Some common square dimensions are 6" x 6" or 6" x 5 1/2". An example of how to properly specify a square format fold to the printer would be: "4-page Standard, square format," followed by the finished dimensions.
There are special considerations for a square format piece—if planning a piece that will go through the mail, please note that square mail will require extra postage.
Folding/Imposition Exercise
Imposition is the process of positioning pages in a document in a way which allows them to be printed on a large press sheet. When the sheet is folded, the pages read consecutively.
In this exercise, you need to create a 64-page self-cover book by folding two provided press sheets to a finished size of 7" X 10". You'll repeat exactly the same folding on the second sheet as you did on the first. Insert one signature inside the other. You need to number the pages. When you paginate your book, make sure the numbers are written in the same direction as the text would be on the page. (I'll explain this in class.)
Make sure you write your name on both signatures. Clip them together and place them in an envelope with an ID tag on it. This will be due at the start of next class.
