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  • DIAZO PHOTO EMULSION METHOD

  • The Photo Emulsion Method is one of the most exciting techniques of screen-printing because

  • it offers a wide range of possibilities. With this method you can print fine line drawings,

  • various lettering techniques and photographic half-tone positives.

  • All methods of photographic screen printing require three things:

  • 1. A screen prepared with a light-sensitive Photo Emulsion coating.

  • 2. A film positive, or printed transparency 3. A light source that will enable you to

  • transfer the opaque positive image to the light-sensitive coating on the prepared screen.

  • Note: With the photo emulsion method you must use Speedball’s polyester screens and screen

  • fabric.

  • Step One is the mixing of the photo emulsion.

  • There are three key things to remember at this step.

  • 1. Use gloves.

  • 2. It is absolutely necessary to add water to the sensitizer and completely dissolve

  • the paste into water. You should see a color change in the sensitizer after mixing with

  • water.

  • 3. Thoroughly mix this solution with the emulsion. The color will change and the light blue emulsion

  • will now have a green tint. Refer to the Diazo System Process by following the mixing instructions

  • given on both containers.

  • (Always store the sensitized emulsion in a cool and dark place. Shelf life for the sensitized

  • emulsion is 4 weeks at 90°F, 8 weeks at 70° F, and 4 months when refrigerated.)

  • You are now ready.

  • Step Two is the coating of the screen.

  • This step DOES NOT HAVE to be done in a dark room.

  • Coat the screen by first adding the emulsion to the screen topside and spread it evenly

  • and thinly across the screen with the squeegee. Use more solution where necessary, spreading

  • evenly with the squeegee.

  • Repeat this process on the backside of the screen, working to achieve an even continuous

  • coating on both sides of the screen fabric.

  • Return any of the excess solution to your mixing container.

  • Do not allow excess solution to build-up, as extra solution will affect proper exposure.

  • Step Three is the drying of the coated screen.

  • In an area AWAY FROM DIRECT LIGHT AND HEAT, set the screen to dry in a horizontal, bottom

  • side down position. Elevating the four corners of the underside of the frame, allows the

  • screen to dry thoroughly.

  • If more than 300 prints are to be run, it is best to apply a second coating of the sensitized

  • Photo Emulsion to the bottom of the screen after the first coat is dry. Remember, for

  • best results, aim for a smooth, THIN coating of the solution.

  • Once the coated screen is dry, it must remain in a darkened area until it is ready to be

  • exposed. (Use a fan to greatly speed up the drying of the emulsion on the screen.)

  • Note that with Speedball’s Diazo System, the maximum allowable time between application

  • of the sensitized emulsion to the screen and exposure of the screen is four weeks at room

  • temperature, in a completely dark environment.

  • Step Four is preparing yourpositiveart to burn onto the screen.

  • A “positiveis any opaque image usually black, on transparent or translucent film.

  • There are many ways you may choose to prepare the film.

  • An excellent transparent film for this purpose is acetate.

  • Printed opaque art can be created on sheets of acetate with a photocopier, laser printer,

  • and you can create your own artwork with Speedball’s Super Black India Ink and an artist’s brush

  • or Speedball Drawing Pens or enamel paint pens. The graphics must be very opaque to

  • light. Any art that allows light though will not create a clean image reproduction.

  • Copy machines have the capability of reproducing very opaque prints on film or acetate and

  • tracing paper. In order to satisfactorily produce a positive image using a copy machine,

  • the following conditions must be met: 1. You must have Black and White line art.

  • 2. Images should be in high contrast. 3. Transparency prints must be opaque.

  • Using a desktop computer, you can download many copyright-free images suitable for screen-printing.

  • You can print that image directly onto a transparency material. To help guarantee a good exposure

  • burn, you should layer 2 transparencies together.

  • One very important note: Check that the film or acetate used on the photocopier or laser

  • printer is rated for this type of usage.

  • Step Five is the set-up of the Light source for the burning of the screen.

  • To set up yourlight stationplace the screen on top of a piece of black paper and

  • center it 12 inches directly below a 150W clear incandescent bulb or a BBA No.1 Photoflood

  • bulb. The BBA No.1 bulb is preferable, particularly for fine graphics because the exposure time

  • is less. You can also use a light table with 20W florescent tubes. All light set-ups should

  • be fitted with a shop reflector.

  • An exposure time chart can be found in the Chapters section of this DVD.

  • Step Six is the exposure of the screen. Before you remove the sensitized screen from

  • the dark drying area, make sure everything you need to print with is on hand.

  • You should have your light station lamp ready.

  • The positive film transparency should be placed in contact with a dry coated screen by the

  • following methods:

  • 1. Attach image to the screen with cellophane tape.

  • 2. Lay a piece of clear glass, Lucite, or Plexiglas on top of the positives. This is

  • the preferred method and it is necessary to use this technique if thin lines or lettering

  • less than a ¼ inch in height is to be printed. When you are sure all positives are in place

  • and flat against the fabric, you are ready to expose the screen.

  • Expose your screen based on your light source and the exposure equipment used.

  • Step Seven is the final step.

  • Now that the screen has been exposed, apply a forceful spray of luke-warm water to both

  • sides of the screen. DO NOT USE HOT WATER.

  • A spray nozzle on the end of a short hose in the work sink is preferable.

  • Concentrate the spray on the light images on the topside of the screen. After a few

  • minutes, these areas will becomeopen”. Continue spraying until all unwanted emulsion

  • is gone. Perform final spraying with cold water.

  • Once you have completely washed the screen, let it dry thoroughly in a flat level position.

  • Hold the dry frame up to a light and check for pinholes.

  • These can be covered with Speedball® Screen Filler or pieces of masking tape stuck to

  • the bottom of the screen.

  • If Screen Filler is used, let the screen dry again.

  • Now the screen is ready to print.

DIAZO PHOTO EMULSION METHOD

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B1 screen coating opaque exposure dry photo

Photo Emulsion Method

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    Chihyu Lin posted on 2014/11/19
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