A detailed analysis of the pre press process of th

A detailed analysis of the prepress process of T-shirt printing (traditional practice) (I)

I. Basic knowledge of T-shirt design

to carry out t-shirt design, we must first master the basic process of T-shirt printing, and also understand the printing technology level of the producer and the T-shirt printing equipment used. For example, T-shirts with colored fabrics have always been printed with water-based mastic paint, but if the producer has mastered the production technology of thermosetting plastic printing ink and purchased the corresponding equipment (mainly T-shirt printing machine, infrared dryer, infrared T-shirt oven, etc.), he can use thermosetting ink to print T-shirts with colored fabrics for processing. The glue printing and thermosetting ink printing have different requirements for the design of the pattern. The glue can only be used for simple color block pattern printing, while the thermosetting ink can be used for transitional step printing, which can not only be used for primary color printing on white T-shirts, but also for special color printing on dark T-shirts. If the pattern designed by the designer is inconsistent with the technical process mastered by the producer, the printed pattern cannot reach the original intention and effect of the designer, or even cannot be printed at all. Therefore, T-shirt designers must be proficient in T-shirt printing process, especially excellent T-shirt designers will pay close attention to the development and technical characteristics of the latest T-shirt printing materials and printing equipment in the world, so as to produce novel and unique T-shirts with the latest scientific and technological achievements at the fastest speed

in industrialized countries, T-shirt designers are often independent professionals. They set up their own T-shirt designers or companies, and they sell their own ideas and designs to T-shirt factories, T-shirt operators, advertising companies and other customers. Such t-shirt design companies often first consider three issues when designing: 1 Customer requirements; 2. Adopt the latest T-shirt printing technology to achieve a unique and brilliant artistic effect; 3. The best cost profit margin

color gradient printing technology has been popularized and developed rapidly in China in recent years, and plate printing technology has been gradually adopted in T-shirt printing. At the same time, the popularity and competition of computer desktop publishing system have greatly reduced the production cost of color separation and addition. Now it is very convenient and cheap for us to make color separation and addition films. This progress is like the progress from letterpress printing to offset printing in the printing industry. T-shirt designers get rid of the design restrictions of color block patterns (except for glue printing), and have more creative space. Whether it is photo effect, painting effect or spray painting effect, otherwise a series of problems will inevitably appear in the future. Now they can be easily reproduced on T-shirts through plate printing technology. This is the progress of contemporary science and technology, but also for T-shirt designers to master the requirements of digital technology

II. Making of plate making manuscript

plate making manuscript can also be called black-and-white manuscript, color separation manuscript, plate making negative, etc. Its main function is to dry the photosensitive printing stencil. Therefore, the plate making draft must be drawn on the light transmitting substrate, and its image is an opaque ink layer (black or red). The light transmittance of the substrate and the shading density of the ink layer are the key indicators to determine the quality of the plate making draft. The formation of plate making draft image mainly adopts manual drawing, manual or mechanical engraving, photosensitive copy, laser Phototypesetting, printer printing and other production methods, but there are also ordinary paper drafts that are used as plate making drafts after light transmission treatment (such as oiling)

1. Color separation

there are two main types of color separation methods: spot color separation and primary color separation

primary color separation refers to the decomposition of natural color images into three primary colors (magenta, cyan, and yellow), so as to carry out three primary color price adjustment printing, so as to achieve the purpose of restoring the image of the object, which remains unchanged. Any color in nature is composed of three primary colors, so in theory, the use of green will be the direction of nature works' efforts to develop. The three color plates of magenta, yellow and yellow can print realistic restored images, but due to the limitations of various factors, it is difficult for the three primary colors to achieve this. Therefore, four-color printing is usually used in printing practice, that is, three primary colors plus black. In recent years, in order to restore colors more realistically in the world, six color printing and seven color printing have been developed on the basis of four-color printing. The principle is to separate the composite colors of orange, purple and green on the basis of four-color printing, so as to reduce the gray level in printing and achieve the effect of high fidelity. In order to distinguish from spot color printing, we usually call the reduction printing of natural color patterns through optical or digital technology as primary color printing (which can be understood as reduction color printing), which is different from the concept of primary color (only three primary colors) in optics and chromatics

it is worth mentioning here that primary color printing and spot color printing are not incompatible. Internationally, the latest development of color printing is the combination of primary color and spot color for special primary color printing, which gives full play to the advantages of the two, complements each other, has a higher printing effect, and belongs to high-quality printing. This is also allowed to play in T-shirt printing. The author once saw a T-shirt made in the United States, with a total of 12 colors of printing. In addition to four primary colors, it is also equipped with eight sets of spot colors, including gold and silver and other colors, especially foam printing and crystal paste printing. Its effect is not only very three-dimensional, but also shiny in special parts, which is really amazing

professional T-shirt designers usually design the composition according to the principle of spot color or primary color. After receiving such a design draft, they can only separate colors according to their requirements. However, there are also some non spot color designers or customers who only provide originals such as various pictures or drawings and require them to be printed on T-shirts. In this case, we need to communicate with designers and customers: first of all, we need to understand their creative intention and what effect they want to express. In order to achieve this effect, is it better to use spot color printing or primary color printing? Even primary color printing? At this time, T-shirts with different printing methods should be provided to them so that they can understand and choose; Secondly, we should tell them the production and processing costs of spot color printing and primary color printing, so that they can make decisions according to their investment plans

2. Color separation plate making draft

color separation plate making draft is used for photosensitive production of corresponding color separation plates. The quality requirements are: first, the light transmission performance of the substrate is good; second, the image shading density is high; third, the alignment and chromatic accuracy between the color separations should be accurate; and the edges of the image lines should be bright and clean, and the dots should be full and clear

(1) the positioning of multi color separations generally uses the cross hairs as the benchmark, but it is often easy to put the separations upside down in the printing process, or the front and back are wrong, or the graphics are upside down. We use the left positive and right oblique method to mark the positioning cross hairs, that is, the left is + and the right is x, so as to eliminate errors

(2) because the red tear film is expensive and difficult to buy, it can be replaced by red self-adhesive paper. As long as the red self-adhesive is only pasted on the PVC film (on the original or line manuscript), it can be engraved with a knife. Since the light transmittance of red self-adhesive paper is far less than that of red tear film, the light of the lighting drawing table should be brighter. In this way, the price is low, the shading effect is good, and the lines are bright and clean, not afraid of water and humidity. What's better is the convenience of modification - as long as it is removed and re engraved, while the red tear touch can't be re engraved, and the ink painting can only be slightly modified

(3) if the patterns of the two printing color plates are not connected or overprinted, you can consider painting the two color drafts on a diaphragm, and drying two plates when printing. Version a closes the B pattern, and version b closes the a pattern. Even secondly, you can sun a plate, add an ink tape between ab patterns, and print two colors at the same time with a plate

3. Manuscripts

manuscripts are the most basic traditional methods, mainly manual drawing and manual engraving

manual drafting tools mainly include: Lighting drawing table (OA table), drawing ink pen, drawing compass, triangle board, curve board, paper cutter, steel ruler, drawing PVC film, PCV film drawing ink, red tear film, red self-adhesive paper, etc. First of all, there should be a light tracing desk. The light source is usually fluorescent lamp. If incandescent lamp is used, frosted glass or a layer of copy paper should be pasted under the glass, so that the light is relatively soft and does not hurt the eyes. If you need to trace at home or in a temporary place, the emergency method is to put the square stool on the ground upside down, put a piece of glass on the four stool legs, and put a desk lamp under it, and you can use it. Drawing ink pens are mostly needle pens with a pen head diameter of 0.2 ~ 1.3mm. To prevent the pen head from blocking, put a piece of hollow cotton (or sponge, etc.) into a bottle, add half a bottle of water, and insert the pen into the bottle when the drawing pen is out of service, so that the pen head will no longer be blocked.%

draw according to the used slurry and overprint sequence. Printing pastes have hiding power, so the graphic contact lines of various color drafts can be overprinted more, and even light color drafts can be used as the base color of dark graphics. If the color of the fabric is darker, it can be considered to play a white background. The drawing sequence of the color separation draft for gel printing is just opposite to its printing process, that is, draw a dark draft first, then a light draft, and finally a white draft

water slurry is mainly used for printing white T-shirts, which is a transparent printing coating. Therefore, the overprint of the touch line between the color separation drafts is 1 ~ 2mm. If there is too much overprint, it is easy to appear the composite color of two-color overprint. The order of painting is to draw a color manuscript with contour lines (usually black), and then draw the manuscript from light color to dark color based on this diaphragm