Postpress Technology 1000 Questions (200-205)

200. What is the revision operation of the dried metal relief?

Scraping with scraping pens to remove dirty, stray, and dead-line paintings: Use a brush to pick up the revised ink made from asphalt paint or paint and turpentine, and fill up the cut-off paintings, warming and baking.

201. Dry metal relief etching solution

Corrosion is the etching of the blank area of ​​the layout, to meet the requirements of embossing.

The zinc plate is etched with dilute nitric acid solution. Its chemical reaction formula is:

4Zn+lOHNO3 (dilute) to 4Zn(NO3)N2O+5H20
The copper plate is etched with ferric chloride solution. Its chemical reaction formula is:

2FeCl3+Cu-CuCl2+2FeCl2 general corrosion methods are the following: mechanical corrosion, etching, pen etching.

202. What are the characteristics of drying metal relief using mechanical corrosion?

The exposed plate is placed in an eroding machine and a rotating water-repellent blade is used to spray the etching solution onto the plate. This kind of corrosion method has large impact force, can continuously remove the salt impurities generated in the layout, and has a strong corrosion effect, and the layout is deep and the contrast is large.

203. What are the characteristics of drying metal relief using etch etching?

Also known as the static rot method, the printing plate is clamped on both sides of the grooved wood board, and the film is immersed in the etching liquid downward (see FIG. 14), and the corroded metal slag and the generated salt can be continuously dropped to obtain satisfactory quality.

In order to make up for the photographic and photo printing defects, an upward facing etching method may also be used.

204. What is the characteristic of the use of pen corrosion etching method for drying metallic relief?

With a fresh pen, apply fresh corrosive solution, and apply a few seconds to the part to be locally eroded. Wipe again with a dry damp cloth and repeat. This method is mostly used to erode downwards and make local corrections to high-profile levels to highlight the correction of bright points and high-level gradations or fading gradations (such as sky clouds).

205. What are the characteristics of the etched zinc relief?

Zinc corrosion must be mechanical. Because nitric acid erodes the colorless and odorless nitrogen oxides produced by the zinc plate, oxygen in the air can produce toxic red-brown nitrogen dioxide. Corrosion machine seal outlet is equipped with a vent pipe, which can emit toxic gases.

Source: "Guangdong Printing" (author / Jin Yinhe: Beizhuang Institute of Graphic Communication)