Screen Printing - Photopolymers versus Direct Emulsion

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Photopolymers versus Direct Emulsion (Diazo-based)

Since the advent of screen printing, some of the printing jobs that are unworkable before are now doable. It is said that screen printing is the most flexible printing technique, since it is used on numerous things. Screen printing can be used when printing on materials like glass, fabric, and even metal.

One very important element in screenprinting is emulsion. There are currently two popular choices for screen printing emulsion: photopolymer and diazo. There is actually a third kind of emulsion that is increasingly gaining popularity: diazo-photopolymer, a crossbreed of the two emulsions.

Diazo emulsion is the first emulsion that was available in the market. Relatively cheap, diazo emulsion remains a popular choice among screen printers. Diazo requires longer exposure and this is mainly because of its weak light sensitivity, the weakest actually among the three emulsion methods. But despite its exposure downside, the Diazo's good results make it worth the wait. Another diazo downside is that it has a greater emulsion over mesh (EOM) compared to photopolymer and diazo-photopolymer. Diazo emulsions require to be mixed, too, because unlike photopolymer, it is not presensitized like photpolymer emulsion. Its sensitizer and its base still needs to be mixed. It is recommended that Diazo emulsions be bought in small quantities because it has a short shelf life.

Meanwhile, photopolymer is everything that diazo is not. Photopolymer requires only minimum exposure because its light sensitivity is higher. This type of emulsion is the preferred emulsion by small businesses, because apart from its minimum exposure time length, photopolymer also has a shelf life that can last up to a year. Unlike with Diazo, photopolymer is already presensitized, so there is no need for mixing substances. Photopolymer, though, is more costly than Diazo.