There are a couple of ways to create your stencil for screen printing. The most common is to use photo emulsion to "burn" your image stencil directly onto the screen. The second is to use drawing fluid and screen filler to hand draw on your stencil. Another is to create a stencil using paper, acetate film, or wax paper to cut the image out of.
The last method is what I use. I like it for many reasons. The primary reason being that I don't have a huge selection of screens to print with so using a cut acetate stencil allows me to reuse a screen. Though burning the image on a screen using photo emulsion allows for a greater degree of detail and durability, if you need the screen for something else you must destroy the burned image and start over.
Acetate film, commonly known as transparency film, is easily available at office supply stores. You can also get larger sheets at art supply stores. Art supply stores also carry acetate film in colors i.e. green and red. I prefer clear, well, just because it's cheaper.
So, let's get started on making a stencil from acetate film. Can't start without your supplies! What you need is an exacto knife, a self-healing cutting mat, acetate film, and an image. Images can either be printed directly onto the acetate film or drawn/printed onto paper which you put under the film as a guide for cutting. For this particular tutorial my image is larger than what my printer can print. What I did was create my image in photoshop and split it in two before I printed it out. I then taped the two seperate print-outs together to create the whole image.
Now that you have your supplies and your image ready to go, it is time to cut. Because the image itself is on a piece of paper instead of printed directly on the acetate you will need to place the image under the acetate. Center the image as best as possible being sure to leave room at the top, bottom and sides where no cutting will occur. Having these areas solid makes the stencil a bit more stable and durable. Tape the paper to the acetate so it won't slip around while cutting.
I like to start cutting around the more detailed "islands" in the image. Islands are the white areas in the image that don't get cut out and are connected to the outer template by "bridges". The particular image I am using doesn't have any real "islands" but rather long "bridges" that will help create detail and depth in the final print. I prefer to cut these areas first because it can involve more fine cutting and having most of the template intact allows for a more stable cutting surface.
As more of the stencil is cut out you will notice that the acetate may slip or bow in the area being cut. A remedy to this is to place a finger or two above and opposite of the direction you are cutting to give the piece stability. Be careful though not to cut yourself with the exacto knife.
Once the cutting is complete the cut out areas need to be removed. When pulling off the cut outs be careful not to bend or rip the areas of the template that will remain. Sometimes a cut was not complete at certain points. When this occurs, carefully take the tip of the exacto knife to this area and gently cut it.
And voila, you have your stencil and you're ready to print!