When it comes to Emulsion for screen printing, you should know that it is important to have a very good quality screen to be able to create beautiful graphics. Since there are several types of emulsion for screen printing available on the market knowing which one is best suited for your job is very important to the quality of work that you would create.
Actually the type of emulsion that would be best suited for your job would depend on you answering a few questions which would be as follows:
- What kind of an experience you have with screen printing and whether you consider yourself to be a beginner or having just enough experience or would consider your self to be a professional.
- Next you would have to consider the kind of exposure unit you have and how it would expose the emulsion.
- You would also have to consider the ink you would be using with that screen.
- Last but not the least you have to consider the environment in which you would be washing out the emulsion.
The answers to these questions will help you in the long run by saving you time and money over experimenting with different emulsions. You can then check on the pros and cons of the different emulsions while comparing them with your previous experience and other resources. When it comes to emulsions you will find that there are two main categories : Presensitized and Diazo or mixed emulsions.
What is presensitized emulsion for screen printing (Photopolymer Emulsion)?
Presensitized Photopolymer Emulsion is a highly sensitized emulsion which exposes very quickly. It has a long shelf life and is useful in exposing fine details. But this kind of emulsion also has a downside to it, by being highly sensitive it tends to expose itself even in cloudy daylight. This means that if you wash your screens outside, this emulsion would overexpose even the blocked out areas on your screen.
The presensitized photopolymer emulsion has a very narrow window in which you can expose your screen and get perfect results. This emulsion is not meant for a beginner because of its exposure window besides which you need an exposure unit with a timer and a dark room in which to washout the screen. Though this type of emulsion can give you great results it is a difficult emulsion to work with and if you do not have the necessary experience, you may run into other serious problems.
Pros of presensitized emulsion
These are the pros of using presensitized emulsion:
- With this kind of emulsion you can expose your screens very quickly.
- These kinds of emulsions also have a longer shelf life of up to one year.
- An advantage of using presensitized emulsion is that you can get great details on your screens.
Cons of presensitized emulsion
Though presensitized emulsions can give you a very finely detailed screen, they come with a few cons. Here are the cons of these kinds of emulsions:
- These emulsions are very sensitive and cannot be used by units without timers. Also the screens need to be washed out in UV free areas which means that you have to have a dark room in wich to wash out your screens.
- Because these kinds of emulsions are very sensitive and take about 10 seconds to be exposed, they can cause washout issues if the screens are over exposed or under exposed.
- Presensitized emulsions are much higher priced than other types of emulsions.
- Another problem with presensitized emulsions is that they tend to have limited resistance to water exposure.
What is Diazo or mixed (Dual Cure) emulsion ?
Diazo or mixed Dual cure emulsion needs to have the diazo powder to be mixed with the base before being used. The diazo powder sensitizes the emulsion and must be mixed with the base prior to printing for the first time. Once you have mixed the diazo powder with the base you can store this emulsion for tow to three months before it goes bad. The best place to store the mixed emulsion is in a fridge but you have to take care that the emulsion does not freeze.
This mixed emulsion takes much longer to be exposed but it is much easier to work with than the sensitized emulsion. It is much more forgiving and can still give you a perfect screen even if you over expose it up to a minute. This means that you can work with this type of an emulsion even if your unit does not have a timer and also you do not need a dark room to wash out the emulsion. Diazo mixed emulsions are also much cheaper than sensitized emulsions and easier to work with for those who are beginners in screen printing. They do give high quality and detail while being more forgiving than sensitized emulsions.
Pros of diazo or mixed Dual Cure emulsions
Here are some of the pros of diazo or mixed emulsions:
- These types of emulsions are much cheaper than the sensitized emulsions.
- They are easier to work with since they are much forgiving to over or under exposure than the sensitized emulsions.
- These emulsions also do not need a dark room to wash the screens since they are not affected by UV light and can even be washed out in daylight.
- These emulsions though do not give as fine a detail as presensitized emulsions, they still offer a good amount of detail.
- These mixed emulsions as compared to presensitized emulsions are very user friendly and can even be used by beginners in the field.
Cons of diazo or mixed emulsions
Though the diazo emulsions are easy to work with they do have a few drawbacks as compared to presensitizes emulsions. Here are the cons of these types of emulsions:
- As compared to presensitized emulsions, the diazo or mixed emulsions have a much shorter shelf life and cannot be stored for a long period of time.
- Also these types of emulsions need to be mixed before being used.
So when it comes to knowing which type of emulsions you can use, it all depends on your experience, the type of equipment you have and the amount of detail you want.