OCT 2 Steps to Creating a Screen By Vimesh Shah Let’s start creating our Screen!!! Oh but wait WHAT are the equipment that are required
· Mesh of appropriate quality an count (Referenced later in the article).
· Frame (Wooden or aluminum)
· Stretching unit, to stretch the mesh to an appropriate tension
· Strong adhesive to stick the mesh to the frame
· Emulsion
· Dryer (To dry the layered emulsion)
· Exposing Unit (Light source mentioned later)
· High pressure water gun. All of these can be easily found on the internet and most of these can be made easily at home
Step 1: Stretching
· Start out with the mesh and stretch it over the frame (use a tension Meter to measure tension (20-25 Newton) General case
· Stick the stretched mesh to the , frame with a strong adhesive.
Step 2: Emulsion Coating
· Clean the Screen so that there is no dust. Let the water dry off.
· Now coat the Screen, print side and the squeeze side with emulsion. (1×2 strokes)
· Check that the coated layer is smooth and evenly applied.
· Remove excess emulsion from the edges as blobs of emulsion take time to dry( do not dry easily).
Exposure the word can be nightmare for many, but not if you understand the science behind it. Exposure is the process where your screen is exposed to a light source so that the coated light sensitive emulsion crosslinks with the mesh. Now the trick to doing this correctly is by selecting the correct type of exposing light source. We should select the light source which can generate light in range of UV lights(WAVELENGHT 350-400 nm).
· Tape the positive film on the print side.
· If you have an exposing unit with a vacuum system good, if not place a black teflon sheet on the squeeze side and start the exposure.
· Now if you are using a industrial black lamp unit(with let say 4 to 6 24”tubes exposure would take from half to 1 minute to expose on a photo-polymer emulsion) For a 500 watt work lamp at a distance of about 2 feet would take 6 minutes.
· Be sure to check the technical data sheet of your emulsion and to ask your dealer about the exposure time for his or her equipment.
· After exposure rinse the screen with warm water(body temp) using a pressure gun at low pressure.
Types of light source used to expose a screen:
This light source can be used for screens that need to be used for short jobs, expose time is very high and the screen may be poorly exposed. Unfiltered black lightrecommended.
500 watt HALOGEN
Their spectral outputis very limited. It is mostly white light and requires long exposure.While you can make screens with them the quality of exposure is inadequate for anything but hand printing.On automatic presses they will exhibit pinholes and stencil breakdown just like weakerfluorescent systems.
1000 WATT QUARTZ LIGHT
Inexpensive compared to a real exposure system,they are sold as shop lights, are used in parking lamps, outdoor lighting and they are really bright. Exposure times are long since the spectral output is poor with most of the light falling in the white light and infrared areas, none of which helps you shoot a good screen.
METAL HALIDE LAMP
Exposure lamps with balancedrare earth elements are the real deal. Generally they are found in industrial strength exposure units where 3k-8k outputis common.We use a 5kw Metal Halide as our benchmark for exposure tests and times. When emulsion is exposedto a strong high quality light the cross linking process is more complete forming stronger molecule chains that cannot be broken by squeegee abrasion, screen flex, or chemical interactionwith harsh inks like discharge or for graphics strong solvent inks.
MESH GUIDE FOR PRINTING
Time to throw some figures at you (General guideline for mesh selection)
· 12 threads per centimetre for printing glitter inks.
· 24 threads per centimetre for athletic, opaque inks, thick puff inks and shimmer ink.
· 34 threads per centimetre for heavy coverage on dark shirts, solid under base prints, puff, metallic, shimmer, transfer printing.
· 49 threads per centimetre for general printing on dark shirts, under base print with detail, print on dark nylon jackets and silver shimmer inks.
· 71 threads per centimetre for multi-colour print on light shirts.
· 90 threads per centimetre for detailed multi-colour printing on light shirts, over printing on dark shirts on dark shirts
· 120 threads per centimetre for process colour printing. * Medium thread Diameter required (T)