What kind of emulsions are there?

Diazo Emulsion

Diazo emulsion is the oldest of the three basic types of emulsion, and consists of a diazo, or light sensitive organic compound, suspended in a resin base. Generally, the diazo “sensitizer” is supplied in a separate container, and the two chemcials must be carefully mixed before use. Diazo emulsions generally have a lower light sensitivity than either SBQ or Dual Cure emulsion, but are also usually less expensive. They are often not used for applications requiring fine detail, as a Diazo stencil tends to be thicker by comparison. Diazo emulsions come in a variety of formulations, with some more or less resistant to water-based, solvent-based, or other types of inks.

Dual Cure Emulsion

Dual cure emulsion features many of the best qualities of Diazo and SBQ emulsions. Like Diazo emulsions, they come with a sensitizer that must be thoroughly mixed with the emulsion before user. Dual cure emulsions tend to produce higher resolution prints than Diazo emulsion, and come in a variety of formulations that feature resistantance to water-based, or other ink types.

SBQ Photopolymer Emulsion

SBQ (Styryl Basolium Quarternary) photopolymer emulsion is sometimes marketed as “one-pot” emulsion. This is because the photo sensitizer is mixed with the polyvinyl base at the factory, rather than by the end user, as is often the case with Diazo emulsions. SBQ photopolymer emulsions are generally the most light sensitive of the three emulsion types (Diazo, SBQ, Dual Cure). This means they expose quickly. However, they are also usually cost more than Diazo or Dual Cure emulsions. Some SBQ photopolymer emulsions feature special resistance to water-based, or other ink types.

Computer-to-Screen Emulsion

Computer-to-screen (CTS) emulsions are designed for use in CTS exposure machines, which generally operate by using computer controlled flashes of UV light to digitally “burn” the image into the stencil emulsion, rather than exposing the emulson through a printed positive, as in the standard screen making process.

Capillary Film

Capillary film is a light sensitive film, used in place of liquid emulsion to create a screen printing stencil. It is so named because when when applied to a screen with water, it adheres to the mesh by capillary action. An advantage of capillary films over emulsion is that they have predetermined, consistent thickness and surface qualities as a result of being manufactured to factory specifications. However, capillary film has the disadvantage of generally being applied from only the substrate side. This means that it does not have the same adhesion qualities as direct emulsions. As a result, stencil wear and durability can be an issue with capillary films on high volume print runs.