UNIT 3 SCREEN PRINTING

                                                    Learning outcomes

By the end of the lesson, learners will be able to:

• Understand the Photographic method of screen preparation.

•    Design the “image/design” to be used for developing a photographic screens.
•    Prepare or “coat” a photographic (photo-chemical) screen.

What is Photographic (photo-chemical) screen method

• This type of screen printing method derives its name from photo which means light.
• It is a printmaking which is done, using a screen coated with a chemical solution(photo emulsion mixed with potassium dichromate).
• The coating solution makes it possible for the effect of light to produce an image on screen.
• A coated screen is said to be sensitized.
• Coating renders the screen sensitive to light penetration.
• The design on the screen is reproduced or printed on a selected surface (substrate), by forcing ink through the screen which bears the image, with a squeegee.

Designing “image/design” used for developing photographic screens.

The inking process

•   Set out the final image to the required size with pencil on a bond paper.
•   Do colour separation if the colours are two or more.
•   Trace the image if it’s one colour or images colour by colour if the image is two or more colours onto kodatrace/tracing paper with black opaque rotring/indian ink using rapidographic pen and sable brush a and allow it to dry thoroughly. This process is termed as inking.

The Computer process

• Sketch your image/design.
• Use your computer make the image/design.
• Do colour separation if the colours are two or more.
• Print out image/design.
• Apply cooking oil/kerosene and use when dried.

Preparing or coating a photographic(photo-chemical) screen.

• Mix 2 or 3 table spoonfuls of photo-emulsion(gelatin, seroset, alcoset, or fixoprint) with 1 table spoonful of potassium dichromate (sensitizer) into an insoluble, photosensitive(sensitive to light) substance.
• Add a little quantity of distilled water and stir gently  and evenly, until the chemical solution is thoroughly mixed.
• Hold the screen erect or standing in a bowl or on a insubstantial.
• Repeat the coating two more times allowing some intervals between.
• Allow coated screen to dry thoroughly and it is ready for exposure.
• Use some of the coating solution/lacquer/acylic paint to seal or cover pinholes after exposure.