The screen-printing process, used today worldwide for printing on garments, was initially developed in China over 1000 years ago and in essence, has changed very little. Developments in materials, inks, and chemicals have refined the procedure but the fundamental way of passing inks or dyes via a mesh screen to the printable surface remains the same.
It’s possible to obtain similar quality prints if you are using homemade manual equipment in your garage or operating large automated machines in a factory – something that may vary greatly though is production times. The next explains the fundamental’spot color’process from somewhere in between, ie dealing with a small-scale professional set-up using an information printing carousel:
The first step is to separate the colors in the design using standard software such as for example Adobe Illustrator or Corel Draw – or to employ the services of any one of several graphic designers advertising on the internet. For every color, a display needs to be produced that will be used in turn with the others to print the image (if printing to dark garments an extra screen to produce a’flash’undercoat of white ink will soon be needed to make the colors in the design more vivid). When the colors have already been separated they are printed to scale in black to acetate sheets, together with registration marks, employing a standard ink-jet printer. The blacked our artwork then needs to be used in the prepared screens.
The typical screens used have a metal or wooden frame with a tightly woven mesh, usually made of nylon or polyester, stretched across them. Screens with various mesh counts are employed with respect to the intricacy of detail in the design (generally speaking higher mesh counts are used to reproduce greater detail as less ink can move across the screen). Screens are prepared by coating them with a photo-reactive (light-sensitive) emulsion and then left to dry flat in an area clear of UV light. Space Force T Shirt When this solution is dry the screens are ready to truly have the artwork’burned’or exposed to them.
A lightbox is currently used which will be basically a package containing UV light-emitting tubes, an obvious glass surface above and a material lid. Each acetate is positioned upon the glass area and a prepared screen laid on top – mesh side down. The material lid is closed and drawn tight within the screen employing a vacuum pump – a timer is then set as the image is developed to the screen. The emulsion on the screen now reacts and hardens where in fact the UV light hits it and stays soft where in fact the regions of opaque black areas on the acetate block it. Once the timer has stopped (anywhere between 1 and 20 minutes with respect to the intensity of UV light) the screen is ready to be washed off with water employing a hose or low powered pressure washer. The water washes away the regions of emulsion that have not developed, creating areas on the mesh for the inks to pass through.
After the developed screens have dried masking tape is applied around the edges to stop ink seeping through areas so it should not. Each screen is then clamped onto a supply of a carousel, mesh side down, and special’plastisol’or water-based ink in each corresponding colour applied on top. To register, or make, the screens a scrap little bit of material is positioned within the platens (boards which support the garments to be printed) and a test print is produced. This is done by forcing the ink through the clear spaces in the mesh employing a hand-held rubber’squeegee ‘, printing the lighter colours first. If printing to dark coloured garments the flash coat of white is printed and then passed under a heat lamp to the touch dry before the colours are applied. The registration marks which can be printed onto the scrap material are arranged subsequently before the finished, registered image is produced. To cure the ink the printed garment is positioned on the conveyor belt of a tunnel dryer and heated to 320 degrees F (160 C). This may avoid the ink from washing away ensure the image will remain for as long as the garment lasts.
If several garments should be printed time is saved by dealing with a colleague, one T-shirt printing and one loading/unloading. To make sure of getting the best reproduction of one’s designs and logos always use the best quality T-shirts and inks that your allowance can accommodate.