1. List the tools and equipment necessary for silk screen printing.
- a) a screen made of porous, finely woven fabric (originally silk, but typically made of polyester since the 1940s)
- b) stretched over a frame of aluminum or wood areas of the screen are blocked off with a non-permeable material to form a stencil, which is a positive of the image to be printed; that is, the open spaces are where the ink will appear.
- c) The screen is placed atop a substrate such as papyrus or fabric.
- d) Ink is placed on top of the screen,
- e) and a fill bar (also known as a floodbar) is used to fill the mesh openings with ink. The operator begins with the fill bar at the rear of the screen and behind a reservoir of ink. The operator lifts the screen to prevent contact with the substrate and then using a slight amount of downward force pulls the fill bar to the front of the screen. This effectively fills the mesh openings with ink and moves the ink reservoir to the front of the screen.
- f) The operator then uses a squeegee (rubber blade) to move the mesh down to the substrate and pushes the squeegee to the rear of the screen. The ink that is in the mesh opening is transferred by capillary action to the substrate in a controlled and prescribed amount, i.e. the wet ink deposit is equal to the thickness of the stencil. As the squeegee moves toward the rear of the screen the tension of the mesh pulls the mesh up away from the substrate leaving the ink upon the substrate surface.
2. Name three kinds of inks suitable for silk screen printing.
There are five different types of screen ink to include solvent, water, and solvent plastisol, water plastisol, and UV curable.
UV Curable
UV curable inks consist of liquid prepolymers, monomers, and initiators which upon being exposed to large doses of U.V. Radiation instantly polymerize the vehicle to a dry, tough thermosetting resin. They also require less energy, overall, to dry or "cure" compared to gas or electric driers.
The down side of UV inks is they can cost as much as three times that of regular inks and must be handled differently than conventional inks due to safety issues. Additionally, solvents are required for clean-up which results in some VOC emissions.
Plastisol Inks
Plastisol inks (both solvent and water based) are used in textile screen printing.
Solvent Inks & Water Inks
Solvent and water based screen printing inks are formulated with primarily solvent or water. The solvent evaporates and results in VOC emissions. Water based inks, though they contain significantly less, may still emit VOC’s from small amounts of solvent and other additives blended into the ink. The liquid waste material may also be considered hazardous waste.
3. List at least three industrial uses of the silk screen process.
Screen printing can be used to print on a wide variety of materials, including paper, paperboard, plastics, glass, metals, fabrics, and many other materials. Some common products from the screen printing industry include posters, labels, decals, signage, and all types of textiles and electronic circuit boards.
4. Tell how bottles and round surfaces are printed.
Non-flat surfaces are printed using a transfer pad like an imprinter with a silicone printing pad.
- Here's a Wikipedia article: http://en.wikipedia.org/wiki/Pad_printing
- Here's a description of the pad printing process: http://www.screenweb.com/index.php/channel/8/id/1609
- Here's a picture of such a device: http://www.imprintor.com/starterset.html
- Here's an animated process: http://www.pdsconsulting.co.uk/Printing%20Process/Pad/Pad.htm
5. Make a design, transfer the design to a screen, and screen print one of the following projects:
a. At least ten greeting cards
b. At least three posters
c. Print a design on fabric
d. Comparable project of your choice
There are two tricky aspects to making a good silk screen print. The first is coming up with a good silk screen, and the second is transferring the design to the card, poster, or fabric. There are a number of ways to create the silk screen, each with a varying level of difficulty, and with varying degrees of quality. Naturally, the more complicated techniques produce the most professional results (at least in the hands of the professionals).
The method that is most likely to result in a successful print with the least amount of fuss, is to directly paint the blocking material on the silk screen. Before doing this, it is best to place tape around the edges of the screen on both the top and the bottom, making sure the inside edges of the tape line up. This will prevent paint from leaking out around the edges of the frame.
Second, place a sketch of the desired design (whether drawn by hand, printed from a computer, or taken from the page of a magazine), and trace it onto the silkscreen with a pencil, being sure that the entire design fits within the limits of the tape. Once the design can be plainly seen, use the blocking paint to begin filling in the negative - that is, you paint over the parts of the design that should not print. Allow the paint to dry.
Hold the screen up to a light to make sure that there are no holes in the negative portion of the screen where paint can leak through. If there are holes, seal them with more blocker. When you are happy with the result, make a test print on a sheet of paper or cardboard. It's a little scary to make your first print on an $18 sweatshirt, so it's a good idea to get comfortable making the prints on a disposable surface. Once you get the hang of it, try it on a shirt (or whatever you like).
After making several prints, you may notice that the screen begins to clog. At this point, you will need to take the screen to a sink and rinse out the paint. You may use a soft brush to scrub the screen lightly, but be careful not to remove any of the blocker. Shake it dry, check for unintended holes, and you should be ready to print some more.
Notes
- You should be able to find screen printing supplies or kits at your local hobby store.
