What are Emulsions?
An emulsion is blend of two or more liquids that are usually not soluble together. They are immiscible. When water and oil are mixed together in a container, they never blend into each other and instead, separate.
How are Emulsions Used in Screen Printing?
Emulsion is used in the screen printing process to coat the front and back of the screen helping the image bind to the fabric. For good results, using the right kind of emulsion is extremely important.
The basic rule of thumb for choosing the right emulsion:
For a water-based and also for plastisol inks, the emulsion must be water-resistant to prevent gumming up or break down. Water-resistant emulsion is designed to withstand the water in the ink and not break down
The different types of emulsions include:
- Diazo:This emulsion is suitable for beginners. It is durable and thick. The color change of the emulsion indicates that the screen has been exposed. It is available in stores selling screen printing supplies and is cheaper than other emulsions.
- Pure Photopolymer:
This is a high quality professional emulsion. The exposure time is more stable and quicker than diazo. Diazo can take 15 minutes or more and the time may differ depending on the level of humidity. A pure photopolymer emulsion takes just a few seconds of exposure and dries very quickly.
To print on a rougher textile like denim or sports clothes, pure photopolymer emulsion is an excellent choice. Numerous coats can quickly be applied to create a thick emulsion layer. The results are good when used with plastisol ink and is durable on T-shirt material. This emulsion is more expensive and found where screen printing supplies are sold.
- Dual Cure:
The emulsions category also include an emulsion known as dual core emulsion. This is a combination of the qualities of pure photopolymer and diazo and has a quick exposure time. After exposure, it changes color. It provides a heavy coating and holds the image. It can be used by inexperienced screen printers, but the quick exposure time makes the use of this emulsion challenging. Dual core emulsion comes in two varieties; one for plastisol inks, the other exclusively for water-based inks.
A basic knowledge of the different types of emulsions available and what the relative strengths and weaknesses of each type are will lead to a better quality products for your customer and improved efficiency for screen printers!