A brief introduction to the process flow of the printing process

The Milo version is a transliteration of the English collotype. The printing of the Feilu version is a category of lithography. Is one of the earliest photolithography, because more use of thick glass as the base, it is also called "glass printing."

On the thick frosted glass plate material, the Milon version is coated with a chrome glue photosensitive liquid. After the negative film and the photosensitive film layer are intimately exposed and exposed, a photochemical reaction takes place and the glue layer hardens to form an image. The depth of the image density is not composed of dots of different sizes, but the degree of hardening of the film varies depending on the amount of light received by the film. The degree of hardening determines the difference in the expansion of the film, and the different degree of expansion results in the formation of fine wrinkles with different densities. The greater the amount of light received, the greater the degree of hardening, the smaller the expansion, the more wrinkles, the less water absorbed, the more ink adhered, and the darker the tone after printing, and conversely, the brighter the tone, thereby reproducing various levels of the original surface, due to The Roland printing is direct printing, so the graphic on the printing plate should be reversed.

The process flow of the stencil printing process is as follows: Grinding glass → Coating photosensitive liquid → Contact exposure → Developing, wetting treatment → Printing.

One, grinding glass plate

A flat glass with a thickness of about 10 mm is ground with a suitable amount of corundum and then a glass plate of the same thickness. The smooth glass plate is ground to a rough surface, cleaned, dried, and coated with a layer of silicon. A mixture of sodium salts (a mixture of sodium silicate and a protein solution) is used as a primer layer. The primer layer is applied to prevent the glass surface from being stained, and the photosensitive film is more firmly adhered to the glass plate.

Second, coating photosensitive liquid

A certain amount of the warmed dichromate gelatin photosensitizing solution is applied to the surface of a glass plate coated with a bottom layer in a dark room, and is placed flat in an oven at 40 to 60° C., and the drying temperature is too high. The air bubbles are generated at a high level, and once the photosensitive film is dried, fine wrinkles are formed on the surface of the photosensitive film. When the temperature is high, wrinkles are formed thicker, and when the temperature is lower, wrinkles are formed finer.

Third, contact exposure

Consecutively adjusting the negative-image negative film and the photosensitive plate are closely contacted and exposed, and due to the difference in the amount of light received by each portion of the plate surface, the photosensitive film produces a hardening reaction of different degrees, and the portion hardened due to light irradiation becomes difficult to absorb moisture and easily absorbs the ink. After exposure, full exposure was performed from the back of the plate to allow the film to adhere tightly to the plate.

Fourth, development, wetting

The exposed photosensitive plate is developed with water, and the adhesive layer of the unexposed part absorbs water and expands and then dissolves, and the swelling effect of the light receiving part is small. According to the density of the negative film, the water absorbs, the high density part absorbs more water, and vice versa, the water absorbs less, and After the action, it is naturally dry.

A humectant based glycerin is used to moisturize the surface of the plate in order to maintain sufficient moisture and prevent water loss.

Fifth, printing

The printing is performed on a dedicated Milo plate type printing press. The structure is a round-squeeze type. The use of hand-dip water, roll ink, and wiping paper requires the ink to have less fluidity and viscosity, and the water resistance of the link material is good. Easy to disperse and soft structure, so as not to damage the printing plate. When the ink is applied, black ink is used for the reaction roller. The roller color ink, because the expanded portion of the printing plate layer absorbs a lot of water, it is difficult to absorb a large amount of ink, and a large amount of ink is present on the concave portion of the plate, which can perform printing with a large density. The temperature and humidity requirements for the environment during printing are stricter.

The shades of the prints of the Minami version can faithfully reproduce continuous tone images. The effect can exceed that of lithographic and letterpress prints. It is suitable for high-quality prints. It is precisely due to this feature that the oldest photographic method can be used. Maintain the continuation of this process. In addition to being printed on paper, it can also be printed on silk and silk. Because the plate base is made of glass, and the printing part and the blank part are all gelatin, the printing power is not high. Generally, a printing plate can only print about 500 to 3,000 copies, and no more than 5000 copies. Therefore, it is not appropriate to print urgent and high-volume products.