What Does a Photoengraver Do?

Photoengraving is a chemical processing method for making metal printing plates by using the technology of photocopying and chemical etching. Its principle is to scale the required text and images on the base film as required, and then attach the negative film to a metal plate coated with photoresist for exposure. After development, the required text or image can be formed on the metal plate. Photosensitive film. The adhesive film is then treated with a resist to make it into a thin layer of enamel with strong acid and alkali resistance. Then, the metal plate is immersed in a nitric acid or ferric chloride solution, and the metal surface without the enamel film is corroded and dissolved to form a printing plate with protruding characters or images.

Photoengraving

In 1822, Niepce in France first carried out a photoengraving experiment. In 1839, Ponton of Scotland elaborated modern photoengraving methods. In 1850, Gillot in France invented the photoengraving method of copper-zinc plates. In 1948, the United States invented the powder-free etching method, and photoengraving began to be widely used.

Photoengraving is the basis of processing processes such as photolithography and chemical engraving.

Photoengraving is the main method of modern silk-screen printing. It uses photographic equipment to shoot the text and patterns to be copied on the photosensitive film according to requirements, so as to obtain the positive plate for silk-screen printing.

As the photographic technology is applied to screen printing, the scope of screen printing and screen printing is expanded. Photographic production of master plates can not only provide very fine lines and text master plates, but also can reproduce complex colors and tonal patterns to produce color separation master plates that meet the requirements of screen printing plates. Therefore, photographic plate-making occupies an important position in the silk-screen plate-making process.

The silk-screen photoengraving process can be divided into three categories: line photography and text draft photography; monochrome mesh color photography and color mesh color separation color photography.

The following briefly introduces the specific content of each process of photo platemaking:

The whole manuscript. Organize the manuscript, determine the proportion of spring style, and determine the rules.

Take pictures. Use photographic equipment and equipment to take monochrome or color separations of the original.

development. The exposed film is developed in a developing solution. After the photosensitive film is exposed, the silver halide in the emulsion layer is affected by light to form a latent image. After the chemical treatment of the developing solution, the latent image becomes a visible and clear image. Commonly used developing solutions are composed of developer Mittal (also known as Elun), Chinuni (also known as Hyder, scientific name hydroquinone); protective agent sodium sulfite; accelerator sodium carbonate; inhibitor potassium bromide and the like.

Fixing. Fixing is to keep the developed silver image unchanged for a long time. The principle is to fix it. The unsensitized residual silver halide on the photosensitive film is dissolved and removed to obtain a fixed image. The fixing solution is generally a sodium thiosulfate (soda) solution. In order to prevent the developing reaction of the photosensitive film in the fixing solution, a certain amount of weak acid can be added to the ordinary fixing solution to make an acid fixing solution. The pH value of the acid fixing solution should be maintained between 4 and 6. In order to enhance the mechanical strength of the photosensitive adhesive, a certain amount of hardening agent such as potassium alum, chrome alum, etc. can be added to the acidic fixing solution to make a hard film fixing solution.

Wash. Water washing is divided into intermediate washing and final washing. The intermediate water washing is performed after development and before fixing, which can play a role of stopping the display and protecting the fixing solution; the final water washing is performed after fixing, and its role is to wash off the fixing process. Soluble double salt produced on photographic film. The washing water is preferably flowing water, and the water temperature should be maintained at 16 to 24 ° C. [Recommended Related: Wash the net water] Use the photographic method to make the master plate, the operation is simple and fast. In recent years, the advent of automatic developing machines and automatic fixing machines has gradually made the process of photoengraving and platemaking mechanized and standardized.