In the offset printing process, controlling the ink-water balance is a key link.
Ink and water are not absolutely incompatible. In the actual printing process, the ink and water are squeezed between the rollers and the ink rollers and fuse together to emulsify the ink. There are two types of ink emulsification: when the water is large in ink, the formation of "oil in water"; when the water is small in ink, the formation of "oil in water".
Excessive moisture levels cause various undesirable conditions, such as:
1. Under the effect of mechanical pressure, the ink is emulsified to reduce cohesion and water resistance. The ink's adaptability deteriorated and its delivery was abnormal.
2, due to the emulsification of the ink, so that the ink becomes lighter, the viscosity decreases, the adhesion is weakened, will also make the network point deformation, resulting in paste version, dirt track.
3, water over ambassadors absorb excess water in the transfer process, so that the printed sheet is easily deformed, resulting in overprinting is not allowed.
4. The large moisture content in the ink after offset printing will inevitably affect the drying of the ink layer of the printed product, which will affect the production of the next process, and will also easily cause the dirt on the back of the printed sheet.
Therefore, in the offset printing process, the operator must pay close attention to the status of printed products, layouts, and related parts and components. When the water content is too large, it must be promptly resolved to reduce the loss of waste products caused by excessive moisture.
To identify the size of the water, first look at the surface water. This is mainly based on the operator's experience. In general, the water is large, and the amount of reflected light on the plate is strong, and the side view is bright. On the contrary, the amount of reflected light on the plate is weak and the side view is weak. If the moisture is too large, you can also observe the following points:
1. Printing products that continue to be printed after a short period of stoppage are more different from inks before shutdown.
2. The printed paper curled soft and weak, and was missing.
3, imprinting outlets empty, biting mouth wave was a pale, dark and dull ink.
4. There are tiny drops of water on the transfer roller and there are also drops of water in the ink fountain.
5, the layout of the buoys, the water in the longer version of the machine is still not dry.
6, in the rubber roller at the tip of a water shadow or water droplets.
7. Scoop ink on the ink roller with a knife. There will be small drops of water on the ink knife.
Obviously, when the moisture is too large, it must be adjusted in time to reduce the amount of water transport. At the scene, we often use a simple adjustment method: that is, a coated paper whose length is determined by the length of the area where the layout or printed product is judged to have a large amount of water, a width of about 130 mm, and a width direction A paper sheet with a width of about 40 to 50 mm on one end is evenly cut out in a zigzag or strip shape, and then the side of the shear is pressed against the surface of the water roller, and the unswept end is fixed on the cross bar of the machine table or the sink On the edge. In this way, due to the fact that there are paper strips resting on some surfaces of the water roller, the paper strip will weaken the water transfer on the surface of the water roller as the water roller rotates. This results in a large adjustment of the water volume. Obvious, simple and practical.
If the water content is too small, it will cause the increase of the field density value, which will result in the enlargement or deformation of the graphic image dot area, resulting in the paste plate, the blank part being dirty, and the level missing. At the scene, if the water content is too small and the above-mentioned unfavorable phenomena occur, the amount of water used must be increased. Sometimes it is also possible to use hand-assisted watering, that is, spraying the water directly on the surface of the water roller at intervals to balance the water and ink.
There are many factors that affect the balance between water and ink. To control the balance between water and ink, it is generally necessary to grasp the principle of less water and thicker ink. Less water refers to the fact that the blank part of the layout is not sticky; thick ink refers to the increase in the amount of ink that is built on the basis of less water. In the printing process, the most taboo is the big ink. When considering the amount of water, the area size of the layout, the thickness of the ink layer, the properties of the printing paper, the ink properties, the type of printing plate, the speed of the machine, the temperature and humidity of the workshop, the pH of the fountain solution, and the ink should be considered. It depends on the adjuvants added.
(Author: Chen such as)
A coffee table is a low table designed to be placed in a sitting area for convenient support of beverages, remote controls, magazines, books (especially large, illustrated coffee table books), decorative objects, and other small items.
Most coffee tables are made of wood (though faux wood tables are increasingly common) or glass and metal, typically, stainless steel or aluminum and may incorporate cabinets or drawers.
Coffee tables were thought to initially be constructed in Renaissance England.
Origins
Japanese style coffee table.
In Europe, the first tables specifically designed as and called coffee tables, appear to have been made in Britain during the late Victorian era.
Couch and coffee table in a hotel room
According to the listing in Victorian Furniture by R. W. Symonds & B. B. Whineray and also in The Country Life Book of English Furniture by Edward T. Joy, a table designed by E. W. Godwin in 1868 and made in large numbers by William Watt, and Collinson and Lock, is a coffee table. If this is correct it may be one of the earliest made in Europe. Other sources, however, list it only as "table" so this can not be stated categorically. Far from being a low table, this table was about twenty-seven inches high.[citation needed]
Later coffee tables were designed as low tables and this idea may have come from the Ottoman Empire, based on the tables in use in tea gardens. However, as the Anglo-Japanese style was popular in Britain throughout the 1870s and 1880s and low tables were common in Japan, this seems to be an equally likely source for the concept of a long low table.
From the late 19th century onwards, many coffee tables were subsequently made in earlier styles due to the popularity of revivalism, so it is quite possible to find Louis XVI style coffee tables or Georgian style coffee tables, but there seems to be no evidence of a table actually made as a coffee table before this time. Joseph Aronson writing in 1938 defines a coffee table as a, "Low wide table now used before a sofa or couch. There is no historical precedent...," suggesting that coffee tables were a late development in the history of furniture. With the increasing availability of television sets from the 1950s onwards coffee tables really came into their own since they are low enough, even with cups and glasses on them, not to obstruct the view of the TV.[citation needed]
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