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1. **Offset Paper and Its Usage**
Offset paper, also known as offset printing paper, is a high-quality type of printing paper primarily used for offset printing machines to produce book plates or color plates. It is categorized into single-sided and double-sided offset paper and further classified into super-calendered and ordinary-calendered types.
(1) **Raw Materials and Properties of Offset Paper**
Offset paper is typically manufactured from bleached chemical coniferous wood pulp with an appropriate amount of bamboo pulp. During processing, the filling and sizing are relatively heavy. For premium-grade offset paper, surface sizing and calendering are essential steps. Due to the water-ink balance principle employed during printing, offset paper must possess excellent water resistance, dimensional stability, and strength. It is predominantly used for color-printed products and requires a certain degree of whiteness and smoothness to ensure accurate ink reproduction. Common applications include printing picture albums, color illustrations, trademarks, covers, endpapers, high-end books, and notebooks. With the enhancement of cultural and living standards, there has been a growing demand for higher-quality materials in book production. Consequently, more books, periodicals, and notebooks are now printed on offset paper due to its advantages such as whiteness, stiffness, flatness, and fineness. These qualities result in clear text and flat, non-deformable publications. Compared to bare paper and newsprint, offset paper offers superior quality and is highly favored by readers and users. Future market demands will likely lead to a significant increase in the use of offset paper for book and periodical binding.
(2) **Specifications of Offset Paper**
The specifications of offset paper align with national standards GB147 "Dimensions of Base Paper for Printing, Writing, and Drawing." Dimensional errors and skew must not exceed ±3mm. Basis weights commonly range from 60g/m² to 250g/m², with typical values including 60, 70, 80, 90, 120, 150, 180, 200, and 250g/m². Offset paper used for book and periodical printing generally does not exceed 90g/m², while cover paper ranges between 70 and 200g/m². Offset paper's stiffness and smoothness make it easy to bind and process. When bumping pages, any method can achieve good alignment results, and any folding machine can achieve satisfactory folding outcomes, particularly suitable for high-speed operations. However, when designing offset paper books, periodicals, or volumes, it is recommended to limit folds to three or fewer (four-fold designs should be avoided). Folding twice before assembly is optimal for papers weighing 80g/m² or more. This is because offset paper is thick and heavy; excessive folding may cause figure-eight wrinkles or dead folds, leading to uneven cutting edges and book cores after trimming.
When wire-binding books, if the number or thickness of bare paper pages is the same, the wire diameter should be larger. Additionally, the adhesive viscosity should be higher than that used for bare paper due to offset paper's large basis weight and smooth surface. Insufficient viscosity may result in weak bonding or detachment. Hardcover book covers made from offset paper are less prone to flattening or ridging, especially when the cover is thick. After flattening, each sheet may become exposed, and the front opening may take on a rounded trapezoidal shape. Manual tapping and smacking during spine raising may leave unsmooth creases inside the seams, resulting in defective products.
Books and periodicals printed on offset paper are generally of a higher grade. Therefore, the cover material should surpass the book core material to ensure harmonious matching between the interior and exterior.
2. **Dictionary Paper and Its Usage**
Dictionary paper, also known as thin bald paper, is a low-basis-weight paper specifically designed for printing dictionaries. Using this paper reduces the cost of books and periodicals.
(1) **Raw Materials and Properties of Dictionary Paper**
Dictionary paper is manufactured from bleached chemical wood pulp with a small amount of grass pulp, followed by sizing or light sizing and calendering. Since books and periodicals printed on dictionary paper are often dictionaries and reference materials, these publications feature small characters, dense composition, and frequent use. Therefore, the paper must exhibit corresponding strength, folding endurance, and smoothness to ensure clear and beautiful characters and a long service life. Dictionary paper is ideal for printing dictionaries, reference books, scientific and technological literature, and other publications. Its key features include thinness and softness. Publications of the same thickness can accommodate 30% to 50% more text and images, reducing costs.
(2) **Specifications of Dictionary Paper**
Dictionary paper is available in two packaging types: roll and flat. Roll paper typically measures 6000m in length and 787mm, 850mm, or 880mm in width. Flat paper comes in three specifications: 1092mm×787mm, 1168mm×850mm, and 1230mm×880mm. According to national standards, the width and skew of dictionary paper may exceed ±3mm. Commonly used basis weights include 30, 35, 40, and 42g/m², allowing selection based on specific needs.
(3) **Binding Precautions for Dictionary Paper**
Dictionary paper is thin and prone to moisture absorption. Once damp, it may develop water ripples, wrinkles, and curled edges, shortening its service life and complicating binding and processing. Page collision methods should be precise; the staggered method is preferred over the impact method to prevent rough or curled edges caused by excessive force. High-speed or grid-type folding machines should be avoided to prevent tearing and waste. Suction nozzle force during page pairing should be moderate to avoid double pasting or tearing. Cross-locking rather than flat locking should be used for thread sewing, as flat locks may elevate the book back excessively, creating height differences and processing difficulties. When cutting finished products, the α angle of the cutting knife should be smaller than that for other types of paper to ensure smooth cutting edges. The adhesive used is similar to that for bald paper.
3. **Coated Paper and Its Usage**
Coated paper, also known as art paper, is produced by coating and calendering base paper. It is suitable for printing fine and high-end products.
(1) **Raw Materials and Properties of Coated Paper**
Coated paper is a high-grade printing paper primarily composed of bleached wood pulp or mixed with an appropriate amount of bleached stamp pulp to form the base paper. It is then coated (with pigments, barium sulfate, calcium carbonate, sizing agents, glycerin, gloss agents, etc.), dried, and super-calendered. Coated paper is divided into single-sided and double-sided types, with glossy and matte varieties emerging in recent years. Most matte coated paper is imported. Coated paper excels in whiteness, strength, and smoothness, making it the best choice for printing portraits, art albums, high-end illustrations, trademarks, book and periodical covers, calendars, high-end products, and enterprise introductions. Printed products on matte coated paper appear particularly elegant and extraordinary.
(2) **Specifications of Coated Paper**
Coated paper is generally packaged in flat form, with two common formats: 1092mm×787mm and 1230mm×880mm. National standards allow a skew of ±3mm. Basis weights typically range from 80g/m² to 250g/m².
(3) **Binding Precautions for Coated Paper**
Coated paper is characterized by hardness, high surface smoothness, and large basis weight. Publications made from it, such as picture albums, are relatively large, increasing binding and processing difficulty and labor intensity. Strict management is required to ensure product quality. Any folding machine can fold coated paper, but the maximum fold is three times with an air exhaust cut. Two or one fold (followed by covering with the book) is optimal to prevent internal eight-shaped wrinkles. Manual folding is generally limited to two or one fold, with care taken to avoid sharp folding boards and excessive scraping force to prevent scratches. Needle holes during thread sewing should not be too large (for machine locking) or too deep (for hand locking), to prevent movement or glue leakage after gluing. Adhesive viscosity should not be too high (when bonding single pages) to ensure firm bonding without removing the surface coating. When cutting, stacks of books should not be too thick due to the paper's large sliding force and tendency to misalign during alignment. The cutter's α angle is the same as that for offset paper, typically 23°. Coated paper contains many fillers and is not resistant to folding. Once creased or scratched, it is difficult to restore flatness. It becomes brittle under sunlight and prone to sticking together and mold when exposed to moisture, rendering it unusable. Therefore, appropriate temperature and humidity levels in factories and warehouses are crucial.