Offset printing is based on the principle that oil and water do not mix with each other, but water alone has a series of shortcomings that cannot do this task properly. And it cannot be used as a printing solution, in order for the water to be usable in printing, some additives are added to it and the drug is made into water.

Offset It is based on this principle that oil and water do not mix with each other. Areas of the image on the printing surface, for example, the page, must be hydrophilic. At the same time, the non-image areas of the screen should be hydrophobic. The water in the offset printing machine that covers the non-image parts, which is called the wetting solution, must be acidic and its pH should be in the range of 4.8-5.2, which is done by using a buffer solution and adding it to the wetting solution. Ideally, the ink should have a water holding capacity of about 15%.

Ingredients of water medicine:

  • Weak acids such as phosphoric acid, citric acid, lactic acid, cobalt and magnesium salts, buffer, gum, antifoam, magnesium nitrate salt (anti-corrosive) and other necessary materials to increase the ability of emulsification and compound reaction with water and reduce the pH of water between It is 4.8 - 5.2.
  • Buffer solutions that are prepared from a pair of acid and conjugate base such as acetic acid and sodium acetate or ammonium chloride and ammonia to keep the pH of the solution at a relatively constant and predetermined value.

Advantages of using drug water:

  • It is a decrease in the surface tension of water
  • Keeping the temperature constant and optimal
  • Increasing the adhesive strength of water
  • It prevents the compound from reaching non-adhesive surfaces
  • Remove the emulsion
  • Ink viscosity
  • Help the gloss dry
  • It provides the possibility to standardize the metric color parameters of the ink on the print.

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