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Friday, July 24, 2009

Stenciling techniques

There are several ways to create a stencil for screenprinting. An early method was to create it by hand in the desired shape, either by cutting the design from a non-porous material and attaching it to the bottom of the screen, or by painting a negative image directly on the screen with a filler material which became impermeable when it dried. For a more painterly technique, the artist would choose to paint the image with drawing fluid, wait for the image to dry, and then coat the entire screen with screen filler. After the filler had dried, water was used to spray out the screen, and only the areas that were painted by the drawing fluid would wash away, leaving a stencil around it. This process enabled the artist to incorporate their hand into the process, to stay true to their drawing.
A method that has increased in popularity over the past 70 years and is tremendously popular is the photo emulsion technique:
1. The original image is created on a transparent overlay such as acetate or tracing paper. The image may be drawn or painted directly on the overlay, photocopied, or printed with a inkjet or laser printer, as long as the areas to be inked are opaque. A black-and-white negative may also be used (projected on to the screen). However, unlike traditional platemaking, these screens are normally exposed by using film positives.
2. A screen must then be selected. There are several different mesh counts that can be used depending on the detail of the design being printed. Once a screen is selected, the screen must be coated with emulsion and let to dry in the dark. Once dry, the screen is ready to be burned/exposed.
3. The overlay is placed over the emulsion-coated screen, and then exposed with a light source containing ultraviolet light in the 350-420 nanometer spectrum. The UV light passes through the clear areas and create a polymerization (hardening) of the emulsion.
4. The screen is washed off thoroughly. The areas of emulsion that were not exposed to light dissolve and wash away, leaving a negative stencil of the image on the mesh.
Photographic screens can reproduce images with a high level of detail, and can be reused for tens of thousands of copiesThe ease of producing transparent overlays from any black-and-white image makes this the most convenient method for artists who are not familiar with other printmaking techniques. Artists can obtain screens, frames, emulsion, and lights separately; there are also preassembled kits, which are especially popular for printing small items such as greeting cards.
Another advantage of screenprinting is that large quantities can be produced rapidly with new automatic presses (up to 1200 shirts in 1 hour} (The record is over 2000 shirts an hour.) The documented recordfor shirts printed in one hour by a single operator is 1805. Maddie Sikorski of the New Buffalo Shirt Factory in Clarence, New York (USA) set the record on 18 February 2005 at the Image Wear Expo in Orlando, Florida, USA, using a 12-color M&R Formula Press and an M&R Passport Automatic Textile Unloader.


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