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Screenprinting 101, Part III
If you have just stumbled into this article, you have missed the first two parts on the basics of Screenprinting. Part I had to do with the business of screenprinting and Part II was on Artwork, UV Paper (use as a film positive), Screens and Washout. These articles are written with the beginner in mind. The information is intended to be general in scope and written on the basics of screenprinting. I am not writing a book by verse, just an expanded outline on the subject
Remember my motto, If it is flat you can print it. Wood, metal, glass, plastic and paper are a few of the substrates that can be printed. The screens are made the same, just the ink types change. For the scope of these articles our substrate will be cloth such as T-shirts, sweatshirts, jackets, etc. As you may recall, in the last article we prepared a screen and are ready to print.
Setting the Off Contact (Snap Off)
The next step is to set the Off Contact Adjustment. I have found in England and Europe they call this adjustment Snap or Snap Off. No matter what you call it, you still have to do it. Simply stated, Off Contact is an air gap between the bottom of the screen (print side) and the top of the item you are printing.
You need this adjustment so that you can push the mesh of the screen down, by use of a squeegee, to the item you are printing. Push the ink through the openings in the screen onto the substrate. When you are finished, release the downward pressure of the squeegee. This will allow the screen to rise to its beginning position. This should leave the ink on the item and the screen free and clear of the item with no ink stranded between the screen and item, if proper technique is used. The distance of the Snap Off will range from as little as a 1/16 to over 1/4, depending on a few factors.
These factors can be one or all of the following: First, the type of substrate to be printed. Second, the type of screens you are using (metal, plastic or wood). Wood tends to have less tension so you will need a bigger Snap Off than with a high-tension metal screen. And last but not least is your own particular preference. I like a very close Off Contact, where as my partner likes a larger gap or Snap Off setting.
The setting is adjusted in the following manner on a rotary machine:
Secure the screens on the arms of your machine. Lower one of the screens down on to a platen. You will be looking for two things from under the screen: First, look to make sure the screen is parallel to the platen on all four corners. If it is not you must level screen to the platen. This is usually done by the use of wrenches on the screen holder assembly. Go from corner to corner till the screen is level to the platen (Note: It is assumed that all your platens are level. If they are not then level them before starting your Snap Off adjustment).
After the screen is leveled to the platen you can now do your Snap Off adjustment. Put on the platen the item you will be printing. The item thickness is important to this adjustment. If your machine is set up for a T-shirt then when you print sweatshirts the setting will be to close. Put the item you are going to print on the platen. Look above the item and just below the screen. You are looking for a gap between the bottom of the screen (Print side) and the top of the platen. For me the gap is around a 1/16. This adjustment nut is usually on the platen arm that the screen holder arm rests on when in the down position.
Important Note: If you are doing more than a one color print, all the other screens must be done just like the first screen making sure that all screens are level to the platen then adjusting the Snap Off of each individual screen.
The setting is adjusted in the following manner on a Universal System:
Important note: You only have to do one screen no matter how many colors you are doing. It is a one-time adjustment.
So now you are ready to print. This is where you make your money. Printing is the easiest part of this business and I think it is the most fun.
Lets say you are doing a multi-color design. What color do you print first? There are two schools of thought on this subject. The widest used method is to print from the lightest color to darkest color: white, yellow, red, blue and finally black.
Next, chose your weapon (squeegee, that is!). Which squeegee do you use? Squeegees come in different hardness, length and blade designs. For the beginner you will need a medium to hard, square bladed squeegee. The length of the squeegee you will need is determined by the design size. Your squeegee should be larger than the area you are printing. On a small design it should be a ½ over each side of the print and on a large design it should be 1 over each side of the print.
P.A.P. is an acronym for the use of a squeegee when screenprinting. I will now explain it letter by letter.
Pull: You should pull the squeegee over the screen from top to bottom. Start your pull approximately 1 above the print. Do not start in the middle. Stop pulling approximately 1 below the print.
Angle: You will want to keep the squeegee at a 45-degree angle from start to finish. This sounds easy but it is not because of the skeleton make up of your body. When you push your hand out far in front of you and pull your arm back your wrist begins to drop. This is normal. But when your are printing, you start out at the 45 degree angle and begin to pull. If you are not paying attention your wrist begins to drop and your angle starts going down, 35 degrees, 20 degrees, 0 degrees. You want a consistent 45 degrees. What I have found that works best for me is to put one foot a little behind the other and lock my arms and rock back with each pull, lock and rock at the same time. It takes practice but you can do it.
Pressure: This means how hard you push down with the squeegee on the screen. Which in turn pushes the screen down on the substrate. You want to exert enough pressure to feel the platen below. Over pressure will deposit too much ink and under pressure will give you a light print. Again, practice makes perfect.
There are a few factors you need to consider in relation to the amount of ink that you will deposit on the item. How thick is the ink I am using? How much pressure did I use? What angle of the squeegee pull did I use? How fast did I pull the squeegee over the screen? All these factors add and subtract from the ink deposit on the substrate.
When you first begin screenprinting experiment (practice) with different forms of the above-mentioned questions. Find what works for you. Understand the relationships between all of them. This will come in handy as you progress in screenprinting.
Add ink to your screen and begin to practice to print and have some fun.
Ink: Use and Type
When choosing ink, check and read all information carefully. Find out the pros and cons of all inks. See how the ink is to be cured and what chemicals you need to clean up after you are done printing. Heed any precautions in the instructions. We will discuss more about ink in a later issue.
There are two basic inks for the substrate of cloth: water-based and oil- based. The generic term for oil-based ink is plastisol. There are many manufactures of these two inks, but they all work basically the same. I will attempt to explain the differences when working with, printing with, and curing both inks.
Water-based inks are used more in England and Europe than plastisols are. In the United States, it is just reversed in usage.
Water-based ink dries (cures) by leaching the water from the ink. This leaves the pigment dried and imbedded into the fabric. The ink will dry on its own without the aid of a dryer. Many printers use a dryer for water-based inks. This increases production of garments. The ink can also be activated to aid in the drying of the inks. The largest problem you have when you print with water-based ink is that all the time the ink is in the screen, water is evaporating in the air. You must be aware of this and not let the ink dry in the screen. Most printers keep a squirt bottle next to the screens to mist the screens to add water to the ink to keep it from drying.
In most cases, when you start a print job you finish it completely to keep from having problems with ink drying in the screens.
The advantage of the use of plastisol is that it never dries (cures) in the screen. You can leave it an hour, day, week or months and it will never dry. The colors tend to be very bright when used. It is very easy to work with. When you are done with your job just scrape up the extra ink and return it to the container to be used again.
It can be a belt dryer or an area dryer (flash dryer).
When I started I used the oven in my house. These will all work. I read an article that estimated that flash dryers cure about 80% of all the shirts that are printed in the United States.
In the Universal All-In-One system we use a flash dryer along with an all aluminum platen to give it even, top and bottom heating and curing. Many different and varied systems work in the curing of garments. You decide what works for your screenprinting company.
In our next segment, Screenprinting 101, Part IV, we will finish basic screenprinting. This final article will include testing of garments, clean up, the use of environmentally safe products, pricing, other inks and applications and more.
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