DESIGN

A Specific design to be produced can be reproduced from a variety of submitted formats. Artwork can be taken direct from disk, email, scanned from original painted drawings and redrawn from scratch to a brief. Artwork has to be seperated into individual colours.

COLOUR SEPERATION

The Artist/colour seperator first has to identify all the different colors in the design. Each colour has to be separated from the other because the printing process dictates that colours have to be printed individualy. There may be colors that are to be printed on top of another color especially in 4 colour process designs these have to be separated.

A layout is made up for the specific design and for each colour design a positive film is produced by sending the required layout electronically to an imagesetter. Each colour is sent down as different angles epecially 4 colour process and half tone work, the angles stop a clashing on the screen when the film is exposed on the screens. The imagesetter images the design onto a roll of film which once printed down is processed using a combination of a developer, fixative and water. Film positives for each colour have now been produced. A covercoat film is also needed (see below) which is a solid impression of the design. Each film has registration marks in the 4 corners of the filmwork to allow the printers to match up all the colours in printing.

Several images of the same design in one layout or images of different designs in one layout can be produced if the colors are similar/compatible in the designs. This will enable you to print either several of the same design in one layout or several images in one layout or maybe you can have some of few images. This will depend on the size of the your layout and similarity of colors between designs.

SCREENMAKING

Once the filmwork is ready it has to be decided what mesh thickness screen is required to print the design. This will depend on the colours, half tone of color, thickness of line. The thicker the colour the lower the mesh size required and vice versa for half tone designs.

Normally, for solid colours 90T or 100T meshes are used, 120T or 130T mesh are used for half tone, 4 colour process and precious metal designs.

The required mesh now has to be prepared to apply a emulsion coating or capillary film (for finer work).

The Emulsion is applied to the screens using a trough 2 coats (wet on wet) are required on the printing side and one coat on the squeegee side. The emulsion must then be dried in a controlled environment and must not be exposed to any light.

EXPOSING

Making sure that the coating is fully dry the filmwork can be placed onto the screen. Each film/screen must be exposed one at a time. The screen and film is placed on a vacuum table in the exposing machine as this removes even the air from between the films and the screen so that the exposure can be without any interference from foreign particle. A 5 kilowatt exposure lamp is typically used

The exposure time depends on the type of screen being exposed and also the distance between the screen and the exposure lamp.

Once the film has been developed on the screen it is washed out using luke warm water coming from a gentle spray gun (not a jet) Once washed the desired image for printing is left in the screen. The screen once again needs to dry out in a heat dryer.
Any pinholes, etc created from the exposure need to be filled and then dry the filler again on the screen before you are ready to print.

PRINTING COLORS

Printing is carried out on a special waterslide paper which must be kept and printed in a controlled condition to stop any expanstion or contraction.

The colour to be printed must be chosen and mixed as typical colours are supplied in powder form. The powder colour is mixed with with a medium which comes in a liquid or paste form. Different mixing ratios and mediums are used for different colours.

Colour matchings are important to carry out at this point before any production runs are carried out.

The exposed screen is set it to the printing machine and the paper is aligned up, the mixed colour is spread onto the screen and a squeege from the machine forces it through the mesh directly onto the paper. Any excess colour is picked up by a scrapper again from the machine. The printed sheets are then placed on a drying rack and allowed to dry. It is ensured that the colour is totally dry before any other colours or covercoat are printed. Once dry other colours are printed ensuring the registration marks match up to the previous printed ones. After all the colours are printed and dry a covercaot can be printed over the design.

COVER COAT PRINTING

A covercoat is an organic media which covers the design and i that carries the design out of the paper to be applied to the wares. When the paper in immersed in water, the water penetrates thru the back of the paper and pushes the film solution with the design out from the paper. Normally this comes in a liquid form paste form and the process of printing is the same as colour, again the covercoat needs to be dried before application typically 24 hours.