Emulsion
Emulsion
Emulsion is the pasty substance used in creating a photographic imprint in silk screen printing. It hardens when exposed to ultraviolet rays or artificial lights of normal intensity. This is why coated silk screens are often kept on areas with safe light mode.
Emulsion is sensitive to sunlight. Occasionally, silk screen can be exposed under the sun so as to harden the emulsion. However, this technique does not guarantee 'well-cooked' emulsion. The present condition of our ozone layer provides us with enough heat for cooking emulsion
Whenever an emulsion is directly exposed to an ultraviolet light, it undergoes crosslinking process. This chemical reaction bonds the molecules of emulsion. The result of the process is a 'skin' of emulsion which can only be achieved if a catalyst is mixed with the paste. This catalyst is produced by the light that supplies UV rays.
An emulsion is categorized by its photosensitizer. An emulsion can be a Diazo an SBQ, or Dual-cure. The former two classifications are widely used in the silk screen industry. Specifically, Diazo has low performance in humid conditions. To avoid the mess, hardeners can be added to Diazo. Meanwhile, the SBQ is more expensive than Diazo and has a longer shelf life. The third type is also a popular choice, but only few screen printers use it for the reason that Dual-cure compensates some of the weaknesses of its predecessors. Dual-cure is more sensitive to light and more resistant to humidity. It reproduces more detailed images compared to the former emulsions.
Emulsion