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The Third Edition continues its long tradition as a useful tool in the ever-changing world of packaging design. It features more than fifty new patterns and new material on the latest advances in closures. This hands-on resource gives designers the advantage they need to successfully meet any packaging challenge. Every pattern has been test-constructed to verify dimensional accuracy and is ready to be traced, scanned, or photocopied for immediate use.
Note: The Figures and/or Tables mentioned in
this sample chapter do not appear on the Web.
Paper is among the noblest of human inventions. It is worthwhile, therefore, to begin with a short history of papermaking.
Before books could be written and preserved, a writing surface had to be developed that was light, not too bulky, and was easily stored. The first great advance was the Egyptians' use of papyrus in the third millennium B.C. Sheets of beaten papyrus stems were fastened together into scrolls, some more than 120 feet long, that could be rolled up for storage. After papyrus came parchment, which was perfected in Asia Minor in the city of Pergamum (from which its name is derived) in the second century B.C. Animal skins had long been used as a writing surface in Greece and Rome, but it was in Pergamum that methods were evolved for the production of a durable, velvet-smooth parchment that could be written on on both sides.
For hundreds of years all paper was made by hand from rag pulp. The use of wood fibers to make paper was discovered in the mid 1800s. In 1840 Friedrich G. Keller in Germany invented a way to grind logs into a fibrous pulp; this method produced a rather poor quality of paper, as all parts of the wood--not just the fibers--were used.
Paper as we know it today was first made in China in 105 A.D. Ts'ai Lun, a member of the court of Emperor Ho Ti, succeeded in turning husks of cotton fibers into paper pulp. This method spread throughout China, Korea, and Japan and as far west as Persia. In 751 A.D. Moslems captured a Chinese paper mill in Samarkand and learned the method of papermaking. They brought the method to Spain around 950 A.D., and by the thirteenth century paper mills had been established throughout western Europe, first in Italy and then in France, Germany, England, and Scandinavia.
The first paper mill in America was built in 1690 by William Rittenhouse near Philadelphia. Sheets of paper were produced one at a time until 1799, when Nicholas Louis Robert developed a continuous process. (This method was patented in England by the Fourdrinier brothers and is known by that name.) In 1817 the first cylinder-type papermaking machine, which can produce a better quality of paper in a continuous process, was invented by John Dickenson.
Today almost all paper is manufactured from wood. Cellulose fibers (which account for 50 percent of the content of wood) are the primary ingredient, followed by lignin (about 30 percent), which acts as a fiber binder or glue.
Water plays an important role in modern papermaking. The manufacture of 1 ton of paper requires about 55,000 gallons of water, most of which is recycled. The papermaking process also uses sulfur, magnesium, hydroxide, lime, salt, alkali, starch, alum, clay, and plastics (for coating). There are two basic types of paper: fine paper for writing and paper for printing and industrial use (packaging).
The first step in manufacturing paper from wood is to remove the bark. The cheapest way to separate the fibers is to grind up the wood by forcing the logs against grindstones submerged in water. The water carries off the wood fibers. In this process everything is used, and the paper produced is of low quality. Another, more frequently used process is chemical pulping, in which the wood is chipped into small pieces, the fibers are extracted through a chemical process, and the unusable material is eliminated. Chemical pulping is more expensive, but it produces better-quality paper.
Chemical pulping creates a pulp, which is then refined by washing and separating the fibers. Refinement, a time-controlled process during which the manufacturer can add various chemicals to increase bonding, texture, and water resistance, increases the quality and strength of the paper. Pigments (for coloring) and coatings (plastics) can also be added at this stage.
Once the pulp is prepared, it goes to one of two types of machines: The Fourdrinier, or the cylinder machine. Modern papermaking machines are huge. They can be as long as a city block and several stories high. They produce paper up to 30 feet wide at a speed of 3,000 feet per minute, resulting in 800 miles of paper a day! The primary papermaking machine is the Fourdrinier. Most Fourdrinier machines make only one layer of material, although they can be equipped to make several layers.
Paper produced by a Fourdrinier machine is smoothed by a stack of highly polished steel rolls, a process known as calendering. The finished paper is then cut, coated, and laminated.
Another frequently used papermaking machine is the cylinder machine. This machine makes heavy grades of paperboard, generally using recycled paper pulp. The pulp is built up in layers. Since paperboard is much thicker than paper, the drying operation is far more extensive. Large steam-heated cylinders drive the excess moisture out of the paper. A coating is then added to create a smooth surface.
The great advantage of the cylinder machine is that it uses large amounts of recycled paper in thick layers to provide strength.
Paper is bought on the basis of the weight (or basis weight), in pounds, of a ream of paper. (A ream is equal to 3,000 square feet of surface.) The thickness of paperboard is expressed in caliper points, which are stated in thousandths of an inch (usually written in decimals). Since most papers are laminated or coated with other materials, caliper points are rarely used today to specify weight. The paperboard used in folding cartons is specified according to the size of the carton or, more often, the weight of the item that goes into it. A glass bottle for 3.5 fluid ounces of fragrance, for example, would require a folding carton with a thickness of approximately 18-24 points.
The thickness of paper can be controlled by means of calendering, pressing, and laminating. High-quality paper is up to 12 points thick; paperboard varies in thickness from 12 to 70 points.
About 20 million tons of fine papers are used for printing and writing annually. Five and a half million tons are used for packaging. Tables 1, 2, and 3 list the major boxboards and papers used in packaging. The uses, content, and characteristics of these packaging materials are described.
Folding cartons are manufactured using three main processes: printing, die-cutting, and finishing.
Several methods of printing are available, they include letterpress, offset lithography, gravure, flexography, and silk screen. Each method is suitable for particular types of jobs.
The letterpress method transfers ink from a metal plate directly to the sheet paperboard. This is one of the oldest methods of quality printing. New technologies have rendered it almost obsolete.
Offset lithography has replaced letterpress because of its production efficiency and high-quality color reproduction. New high-speed presses and computer-aided systems, along with technological advances in inks and coatings, have made "offset" the most popular process for printing on folding cartons. In this process specially sensitized metal plates are chemically treated to accept ink. The ink is transferred from the plate to a smooth blanket roller, which then transfers the image to the paperboard.
Gravure printing is used for high-quality reproduction in large-quantity runs (i.e., millions of copies). Specially etched printing cylinders have cells that accept and store inks. A "doctor blade" wipes off excess ink as the cylinder rotates to the impression cylinder, where the plate cylinder transfers the image to the paperboard. Gravure printing can be accomplished on an in-line web press, which is known as rotogravure, or on a sheet-fed press, which is called photogravure.
Flexographic printing is similar to letterpress printing. It uses a raised positive composition plate made of rubber or plastic. High-speed in-line web presses are used. This process has been associated with low-quality simple line art printing, but recent technological breakthroughs with fast-drying inks have made flexographic printing a low-cost, high-quality method for medium production runs.
Silk screening is a simple method of color printing in which a fabric mesh stretched over a frame is used instead of a printing plate. A stencil-type design is adhered to the mesh and pigment is "squeegeed" through the stencil. A separate "stencil" is required for each color used. (See diagram.)
Printing technology has changed in recent years to better meet the needs of carton manufacturing. Special coatings, varnishes, lacquers, and inks are available to give a bright finish or provide a moisture-proof barrier. Environmental problems have been alleviated by the introduction of water-based coatings and inks.
The process of die-cutting involves creating shapes using cutting and stamping dies. There are three methods of die-cutting. Hollow die-cutting is done with a hollow die, which looks like a cookie cutter. This method is used exclusively for labels and envelopes. Steel rule die-cutting is used when a close register is required. Steel rules are bent to the desired shape and wedged into a 3/4" piece of plywood. The die is locked up in a chase on a platen of the die-cutting press. Several sheets can be cut at once. A flatbed cylinder press can also be used for die-cutting.
The third method of die-cutting uses lasers, which were invented by C. H. Townes and Arthur Schawlow in 1958. (The word laser is an acronym for "light amplification by simulated emission of radiation.") The laser beam, which can be concentrated on a small point and used for processes such as drilling, cutting, and welding, has become widely used in manufacturing, communications, and medicine. Since a laser beam is extremely sharp and precise, the resulting cut is very accurate and clean.
Embossing. Paper and board lend themselves to embossing, the process by which a design image is made to appear in relief. Embossing can be superimposed on printing or done on blank paper (blind embossing) for a sculptured three-dimensional effect. It is achieved by pressing a sheet of paper between a brass female die and a male bed, or counter, both of which are mounted in register on a press. Embossing is generally used on prestigious packages; on packaging for cosmetics, gifts, and stationery; and on promotional materials.
Finishing operations include gluing (using adhesives), windowing (die-cutting), coating, and laminating.
There are several types of gluing equipment, each designed for specific purposes. Right-angle gluers are used for Beers-style and six-corner construction; straight-line gluers are used for side seams and automatic bottom-closured cartons. Automatic tray-forming devices are used in the manufacture of tapered trays, clamshells, and scoop-style cartons. Today computer-controlled multipurpose gluers are used in most large paperboard-manufacturing plants.
A wide variety of specially formulated adhesives are used for specialty cartons made of coated, laminated, and plastic materials. Environmental conditions such as high moisture levels, freezing temperatures, sterilization, and microwaving require specific types of adhesives. Many types of adhesives are available, including self-adhesive and pressure-sensitive labels, resin emulsion adhesive for coated boards, and cold-or hot-melt adhesives for plastics.
Scoring. Paper and board come in flat sheets or rolls. In all papers and boards the fibers are aligned in one direction, called the grain. If they are torn with the grain, the edges will be smooth. If they are torn against the grain, the edges will be ragged. When scoring the fold lines on the comprehensive, only compress the fibers of the paper, do not crush or cut them. Use a dull knife or letter opener. With practice you should be able to score on one side of the paperboard and achieve clean folds. Use white glue sparingly on the glue flaps. A thin coat of rubber cement may be used for covering papers, foils, or fabrics. Caution: rubber cement is highly flammable and toxic; library paste is the preferred alternative.
Cutting. To facilitate the preparation of a packaging comprehensive, lay out the pattern carefully with triangle and T-square on the appropriate paper stock. Two-ply or three-ply are ideal for comps. Use a resilient backboard to score and cut; the chipboard on the back of drawing pads or a self-healing cutting board are great for this purpose. Use a steel straightedge for straight lines. To prevent sliding, glue a few strips of fine sandpaper to the back of the straightedge. An X-Acto ® knife is easy to control for both straight and curved lines. Keep fingers well away from the cutting blade.
Preface from the First Edition.
2. The Folding Carton.
Sleeves, Wraps, and Folders.
3. The Set-Up or Rigid Paper Box.
4. Corrugated Containers.
5. Point-of-Purchase Displays.