Choosing a Screen Printing Emulsion
Choosing the right screen printing emulsion (also known as photosensitive emulsion) is a little like buying a car, they all effectively do the same thing but have different features, methods of use and performance factors which differentiates them.
All of the emulsions react to UV light causing the emulsion to cure and harden. If you are new to screen printing check out our tutorial on YouTube which covers the basics and shows you how to create a stencil using photosensitive emulsion.
There are three main groups of emulsions on the market:-
- Diazo – been in use for many years, the emulsion needs to be sensitised before use. They come with the sensitiser is a separate pot or sachet.
- Photopolymer, sometimes referred to as SBQ Photopolymer (Styryl Basolium Quaternary). The manufacturers mix in the sensitiser with a polyvinyl base meaning that the emulsion is ready to use and you don’t have to mix in a sensitiser. Commonly known as ‘One Pot’ emulsions.
- Dual Cure – a combination of both types of emulsion but mostly (there are some exceptions) need to be sensitised before use. Dual Cure emulsions are the most popular as they incorporate the strengths and weaknesses of Diazo and Photopolymer emulsions.
Autosol 6000 Diazo Emulsion (Authors favourite when using waterbased inks)
| Diazo Emulsion – Pro | Con |
| They have a wide exposure latitude (so very forgiving if you have not got your exposure timings spot on)
Cost effective and reliable
Can be formulated to be water resistant or solvent resistant e.g. if you use waterbased inks you need a water resistant emulsion and if you use plastisol and solvent inks you need a solvent resistant emulsion
We sell Autosol 6000 and Sericol Dirasol 25 |
Less light sensitive than the other emulsions so if you light source (exposure unit / lamp etc) is not stronger you could be exposing for a while!
Not so good for fine detail and halftones (often subject to much debate) , Diazo emulsions are normally quite thick but this is not always the case with all of the Diazo emulsions on the market.
More difficult to reclaim than the other emulsions especially the water resistant variants. |
Chromaline CTR Photopolymer Direct Emulsion
| Photopolymer Emulsions – Pro | Con |
| One Pot – you don’t have to mix in with Sensitiser powder which is unpleasant stuff and is fraught with health and safety issues.
Good for high production print shops
Easy for reclaiming the screen
Can be formulated to be water resistant or solvent resistant e.g. if you use waterbased inks you need a water resistant emulsion and if you use plastisol and solvent inks you need a solvent resistant emulsion
We sell Chromaline, Ulano, Sericol and Macdermid ranges of Photopolymer emulsons |
Very light sensitive – you also need a strong reliable light source e.g. Metal Halide / LED and in some circumstances Actinic / Tube units.
Your exposure timings have to be spot on.
Typically the most expensive emulsion
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Autosol 5000 – Very Popular Universal Dual Cure Emulsion
| Diazo Emulsion – Dual Cure | Con |
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They are relatively quick to expose and work with most light sources
They have a wide exposure latitude (so very forgiving if you have not got your exposure timings spot on)
Cost effective and reliable
Good for fine detail and half tones
Easier to reclaim the screen compared to Diazo emulsions
Can be formulated to be water resistant or solvent resistant e.g. if you use waterbased inks you need a water resistant emulsion and if you use plastisol and solvent inks you need a solvent resistant emulsion
We sell Ulano Proclaim, Macdermid Autosol and a wide range of Sericol and Chromaline emulsions |
Shelf life is not so good as Photopolymers
Most Dual Cure emulsion need to be sensitised, but one pot solutions are now on the market such as Ulano EC
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Ulano EC one of the first ‘one pot’ Dual Cure emulsions on the market, also has 18 months shelf life. No need to add sensitiser – ready to use straight from the pot.
Tips
- Choose the emulsion which gives the right stencil resistance e.g. if you are using Plastisol then choose an emulsions which gives a solvent resistant stencil and water resistant if using waterbased inks. Otherwise you will find your stencil starting to break down.
- Some dual cure emulsions can be used with both water based and Plastisol inks. However if you are using the same emulsion we recommend that you ‘double bake’ . This increases the exposer the screen again after it has initially dried to strengthen the stencil.
- If you are using wate rbased discharge inks for large scale production. We recommend emulsion which is designed for discharge inks such as MagnaPrint.
- Keep the emulsions in the fridge (but don’t freeze) it will extend the usable life
- If you use sensitiser powder emulsions always follow the instructions. Mix the powder in well and leave for a couple of hours to let the air out the emulsion before use
- If you don’t have a strong light source, don’t want the hassle of sensitiser powder. Ideal if you don’t expose many screens then try out a one pot dual cure such as Ulano EC it is rather good