Work with Manufactures, Dealers, & Suppliers To Acquire Test Samples
Screen printing is very much an art / trade skill that takes years to master. It is not like digital printing where you can just push a button and a computer does all of the work. Becoming a great screen printer requires a passion for the process and willingness to continuously research and develop (R&D). Screen printing R&D heavily revolves around testing different chemicals, inks, additives, printable products, and any other material that might come into play during the entire process. Manufacturers of screen printing supplies are always working on ways to improve their products so they are easier to work with and deliver the highest possible quality results. It is also important to remember that every manufacturer claims their product(s) are better than their competitors, but you must test the products yourself to know the truth. If you have a good relationship with a supplier, then they often are willing to supply you with samples at a great price in order to convince you to start using a particular product for future orders.
There are around 20 different types of screen print inks that are used for printing apparel. However, most shops only worry about / carry around 3 types of inks. Most screen printing shops need an everyday ink that is easy to work with, has a great hand (feel) after its dry, and is opaque on the product. The goal is to find the right ink manufacturer/brand that satisfies these three concerns the best. An ink that is very opaque but is extremely difficult to print because it is so thick is not a good situation. So try not to sacrifice hand, opacity, or ease of printing for another, and instead look for another potential ink to use. By far the most common ink color used in screen printing is white. Not only is white the most commonly printed ink color, but it also must be used as an underbase. This means finding the perfect white ink to work with is very important. Many suppliers of ink focus a lot of R&D on making the best white ink to print with as they know it will lead to customers trying their other products. A great white ink follows the same rules as any other ink in that it must be opaque, feel good, and not be difficult to work with. Because white ink contains so much pigment the ink is typically much thicker than any other color. This is not always true and do not assume thicker means more opaque. You must take the time to properly test the inks yourself to see how well they perform and their difficulty to print with.
The screen printing process involves the use of many chemicals, primarily when it comes to preparing and cleaning a screen. The most commonly purchased screen print chemicals are emulsion, reclaimer, degreaser, ink degrader, and haze remover. These chemicals are extremely important in producing a high quality screen and then reclaiming it for future use. It is important that you take the time to test different manufacturer’s chemicals to know which ones are the best. Sometimes changing one chemical can make a huge difference in the quality of the screens or reclaiming process. It is extremely important that whenever you are testing chemicals that you follow the manufacturer’s directions. Chemicals revolve around chemistry and if you don’t follow the directions you will not get the best results.
There are many different types of emulsions that are used to coat screens. Different types of emulsion are used because certain inks will break down some emulsions, and thus the need for different types. However, most shops really only need to worry about using a “photo polymer emulsion” that comes as either a dual or single cure. Dual cure emulsion must first be mixed with diazo, whereas single cure does not and can be used directly out of the container. Because dual cure emulsion has diazo in it, the emulsion is able to hold finer detail in artwork on a screen. Emulsion with diazo also helps increase the exposure latitude. This makes holding detail and washing out a screen easier, even if the burn time is not perfect. In conclusion, the artwork and type of ink being used will determine the type of emulsion to use when coating a screen.
Once you have purchased the emulsion you want to use you must take the time to dial in the exposure times. The length of exposure time comes down to many variables that must be thoroughly tested: type of emulsion, amount of emulsion coated on the screen, the mesh count, and the exposure unit itself. If any of these variables are changed, then the exposure time must be re-determined. Most shops might have around half a dozen screen meshes with each being exposed for a different amount of time, even if they are using the same type and thickness of coated emulsion. Without a perfect stencil the screen printing process does not work. So, take the time to make sure you know the perfect exposure time for each mesh screen to avoid under or over exposing the artwork.
Apparel comes in many different fabric materials with each one presenting their own set of obstacles and hurdles to overcome. Synthetic materials like polyester, nylon, and rayon do not like high heat, and thus must be cured at a lower temperature. Because of this, a performance/athletic type of ink must be used so that it can be cured at a lower temperature and not have dye migration problems when in the dryer. Knowing how each type of material reacts to heat and different types of ink is very handy as it allows a screen print press operator to make better decisions as far as what ink to use in certain situations. Customers want their printed products to have the best possible feel, opacity and durability when it comes to washing. It does not matter how great a custom printed shirt looks and feels if the ink is dry but not properly cured. In order to make sure ink is properly cured onto a garment a simple stretch test should be performed. A stretch test revolves around pulling cured ink horizontally to see if it cracks or stretches. If the ink stretches, then it is good and cured. If the ink cracks, then it is not and needs to be sent down the dryer again at a higher temperature and/or a longer amount of time.