| Screens - Screens are basically a wooden or metal frame with a polyester fabric stretched onto them. The polyester fabric is a lot like the screen on your screen door, It has anywhere from 32 threads per inch, to 385 threads per inch (mesh count). The mesh count we will use is determined by the type of design we will be printing. The finer the detail in the design, The higher the screen mesh count will be. We begin the process of making our screens by stretching the polyester fabric (mesh) onto the frame, and securing it with a very strong glue. Next, We take a light sensitive emulsion (in a dark room) and apply a even coat to the screen mesh. We will let that dry for about 2 hours. After the light sensitive emulsion has dried, We will take the film positive and tape it to the back of the screen mesh. Then, we will place the screen on a device that emits light, Called an exposure unit, and expose the screen with light for a short period of time. The opaque areas (the image) on the film positive will prevent light from exposing the screen. The clear areas of the film positive (where there is no design) allow the light to shine through and expose the emulsion, which makes it impermeable in those areas. Next, we take the screen off the exposure unit and wash it with water. The water will not wash out the hardened emulsion. the water will wash out the unexposed areas where the film positive was opaque. We are left with a screen that has an image in it. The ink will pass through the open areas of the mesh.
Setting up the screens for printing - After making and exposing our screens, We need to prep the printing press for printing. We do this by setting each screen (color) into the press heads (a six color press has six printing heads). We will set them in order by color, light colors first in sequence to the darkest color, usually black last. We need to align each print head to each other to ensure correct registration throughout the printing process. We then add ink colors to the screens and then squeegees to the screen print heads. The squeegees will move across the screen to push the ink through the mesh and onto the t-shirt.
Printing - After the screens are aligned on the press we are ready to begin printing. The automatic printing press can print about 800 shirts an hour. It is a pneumatic press running on 155 lbs. of compressed air. A compressor with a 15 hp three phase motor and a 200 gallon tank is needed to power this press. The screens will stay stationary during the printing process, while the pallets will rotate one at a time in a counter clockwise motion, rising up to the screens after each index for printing, then dropping down to move to the next station. Two people are needed for this operation, one for loading the shirt onto the pallet, and the other for taking the shirt off the pallet, Inspecting the shirt for imperfections and then setting it on the drying belt.
Drying - After the shirt is printed we place it on the dryer's moving belt. The temperature inside the dryer is about 450 degrees. The shirt will only stay inside of its drying chamber for 30 - 40 seconds, enough to heat the shirt and ink to about 350 degrees. There is usually one more person on the other end of the dryer for quality control and folding. Screen Printing ink consists of four major components: Pigment, (for the color). Oil (for the base). PVC's and Plasticisers. When heated to 330 degrees, The oil evaporates and the plasticisers turn the PVC into plastic. Yes, that print on your shirt is a thin coat of plastic bonded to the fabric of your shirt.
Packaging the Shirts - After the shirts are printed and dried, The folder at the end of the drying belt will inspect the shirt for quality and accuracy of the order. The shirts will be folded in dozens and boxed @ six dozen to a box. At 72 shirts per box, it will weigh approximately 36lbs. There are various ways to ship the product. The most common and cost effective way is through UPS. The rates depend on your location. Time of delivery also depends on your location.
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