Like most screen printers you may have found that you are always in search of the perfect liquid emulsion. There are so many different brands, colors and exposure speeds to choose from that most printers just stick with what they know rather than what is best for their shop. Additionally there is all the different terminology that is used to describe the benefits and features of the emulsion. With all of this information to wade through it is easy to be overwhelmed. In an effort to help make things more clearer here is a list of some frequently asked questions about emulsion and the best answers we had for them:1. What color emulsion is best?
a. Color is not important at all when it comes to picking your emulsion. Most people like a color like pink or blue because it provides a good deal of contrast and allows them to see imperfections in the screen more easily. Others like a light colored emulsion because it is easy to see through and makes lining up multicolor prints that much easier. In the end you should consider the emulsion color only after all other considerations have been made.
2. What is the difference between Photopolymer Emulsion, Diazo Emulsion & Dual Cure Emulsion?
a. Photopolymer Emulsion
i. Photopolymer emulsion is a premixed and fast burning emulsion that is available for use with most any screen printable ink. Margin also known as latitude is low for these emulsions but if you have a good exposure unit and you have taken the time to perfect your exposure times photopolymer could be a good choice.
b. Diazo Emulsion
i. Diazo emulsion is a also premixed. These emulsions are typically lower cost than other emulsion and are also usually slower burning because they have a lower light sensitivity. People with weak or homemade exposure units may want to stay away from this emulsion type.
c. Dual Cure
i. Dual cure emulsion is a two part product that has to be mixed thoroughly and left to rest before use. Dual cure emulsions are popular among new and inexperienced printers because they will expose well even if your exposure unit is not great and they allow for a relatively high margin of error.
3. What is exposure latitude?
a. Exposure latitude is basically just the amount of room for error in exposure time that your emulsion will allow. For example: Some dual cure emulsions allow the user to under or over expose a screen by as much as 30 seconds which is considered a long latitude. Conversely, photopolymer emulsions may only allow for 4-6 seconds of under or over exposure which is a very short latitude.
4. What is the solid count?
a. All emulsions are made up of both liquids and solids. Some emulsions are designed to create a very thick stencil while others are designed to be thin. Emulsions that aim to achieve a thick stencil will most often have a higher solid count so that the emulsion is more viscous and builds up on the screen while thin emulsions will keep the solid count low so that the liquid portion of the emulsion is what primarily coats the mesh.
5. Why does the particulate size matter?
a. The particulate size of the solids in the emulsion are important because it is the particulates that will dictate the level of edge definition you can achieve. The best way to think of it is in terms of pixels. The more small pixels you have the clearer the image detail. Some emulsion manufacturers will advertise high solid count emulsions but will achieve the high solid count by using a large particulate. This will lead to an image with substandard edge definition. When considering emulsions you should always burn a circular image into a test screen and evaluate it under a loop to ensure that it holds its shape and does not become a star because the manufacturer has used too large of a particulate in their emulsion.
6. Why should I worry about humidity?
a. In order for a screen to proper expose the emulsion layer must be allowed to dry and adhere to the mesh. Drying the emulsion is little more that allowing the water in the emulsion to evaporate into the air. However, if the level of moisture in the air is equal to or greater than that of the emulsion the water will not evaporate and the screen will not dry. Moisture left in the screen may cause your screen not to expose and may also cause your film to adhere to your screen.
Hopefully these few tips will help ease the confusion and allow you to pick the emulsion that is just right for you and your business. If you need more help please call us anytime at 800-981-7968 and we will be more than happy to help.