The so-called matte hardening (dark reaction) is the sensitized carbon paper, which has a thick adhesive layer thickness after development without exposure. The concentration of potassium dichromate solution is large, there are many free acids, and the difference in animal gums will increase the dull hardening. In the actual production process, care must be taken to promote the matte hardening process of the carbon paper layer. This requires the operator to pay attention to not only the indoor temperature and humidity, but also the storage time of the sensitized carbon paper during the preservation of the sensitized carbon paper, because it is related to whether it can reach the corrosion process The problem of stability and access to high-quality prints. The reaction process inside the glue layer is as follows. Potassium dichromate presents the ionic state in aqueous solution: K2Cr2O7 → 2K ++ Cr2O7--, where: Cr2O7-+ H2O-2CrO4-+ 2H +. Potassium dichromate has different ionic forms in acid and alkaline solutions: when the solution is alkaline, the dichromate ions react in the direction of generating chromic acid ions. Because the oxidation effect of dichromate ion on colloid is stronger than that of chromate ion on colloid. Therefore, in order to weaken the oxidation of dichromate ions and slow down the dark reaction, an appropriate amount of ammonia can be added to the potassium dichromate solution to enhance the alkalinity of the solution. It has three functions: 1. Make the reaction proceed in the direction of generating chromate ions. At this time, the orange potassium dichromate shows a light yellow color, and the dark reaction inside the carbon paper sublayer is weakened. 2. Improve the adhesion of the colloidal substance, so that the adhesive film can be closely adhered to the plate surface. 3. Inhibit the activity of microorganisms to prevent the deterioration and deterioration of the photosensitive solution. After adding ammonia to the photosensitive solution, the PH value is usually between 7.5 and 8.8, which is slightly alkaline. During the drying process, the ammonia gradually decreases and becomes slightly acidic, so the photosensitive performance of the film gradually increases, which does not affect the use effect. Higher room temperature will also lead to the separation of pure chromic acid from chromic acid, for which it is necessary to set up a refrigerator. It must be noted that the humidity inside the refrigerator should be consistent with the relative humidity of the studio. The exposed carbon paper is stored in a certain humid environment for 20h and then re-versioned, it will not be developed. Practice has proved that if the carbon paper is stored for one day after drying the mesh in the wet season, then go to the sun, this carbon paper is often not easy to stick to the plate cylinder, even if it has been attached to the cylinder Shadow coming. Therefore, it is required that the carbon paper that has been printed on the mesh and the positive image should be printed immediately, so as not to delay the intermittent time between the printing and the printing. If the time is too long, it will bring some difficulties to the development and corrosion work. Another method to prevent the dark hardening of the adhesive layer is to add 0.3% potassium citrate as a cleaning agent in the 4% sensitizing solution, which can prevent the latent image of the adhesive layer. The photosensitive performance of the adhesive layer can be improved by appropriately increasing the acidity of the potassium dichromate (K2Cr2O7) solution, but the dark hardening of the adhesive layer will be accelerated accordingly. At present, there is a new type of pre-sensitized carbon paper; the back side is a film of Roto film (Dupont product Rotofilm), which is a patented film used for overprinting. On the other hand, Rotofilm has been used in many printing plants for several years. You can use continuous sun-adjusting images and magenta or gray contact screens to replace the screen-positive images (Durgen Dultgen mesh method of two positive images) Edition). It is a positive film and must be rinsed under dark red safety lights. The magenta screen used in conjunction with Luotu film is exposed through the K2 or # 3385 frosted glass yellow filter, and the continuous dimming image is exposed through the frosted glass # 5840 ultraviolet filter. After rinsing, this membrane has the following advantages: it can be stored for use; it can be shipped without refrigeration; there is no dark reaction and continuous reaction like carbon paper; the density value can be read on the densitometer to check the exposure and Whether the development is accurate or not; only one continuous adjustment image is needed, and there is no need to screen the positive image like the two positive images used in the horizontal screen. It has large contrast characteristics, so it cannot be like carbon paper. Highlight details are often copied. In order to make up for this shortcoming, it is necessary to have sufficient highlights on the continuous dimming chart, otherwise the correct and satisfactory corrosion will not be obtained at a density of 0.30 or 0.35. It is also more sensitive than carbon paper in trimming dyes and ultraviolet factors. After exposure and development, the Luotu film is basically the same as the carbon paper in terms of processing such as printing, hot water development and corrosion. Heating Stove,Heating Furnace,Gas Heating Stoves,Wood Heating Furnace Heating Boiler Ningbo Ifilter Purification Equipment CO.,Ltd. , https://www.nbifiltor.com