B1 Intermediate 1651 Folder Collection
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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 your “positive” art to burn onto the screen.
A “positive” is 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 your “light station” place 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 become “open”. 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.
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Photo Emulsion Method

1651 Folder Collection
Chihyu Lin published on November 19, 2014
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