FLAT BED MANUAL SCREEN PRINTING
A tightly stretched screen of thin silk gauze or nylon on which the pattern is painted in such a way that the unpainted parts correspond to the required design. The unpainted parts allow colour paste to pass through them on to the cloth placed below the screen. The colour paste is applied manually by means of a rubber or wooden squeegee. Squeegee is almost the width of the screen. Squeegee is used to spread colour evenly over the screen.
EQUIPMENT: Tables, Squeegees, Screens, Colour Paste, RFP fabric.
RFP Fabric: Fabric to be pre-processed same as for used for block printing.
Colour paste: Same as used for block printing. To be diluted to required consistency.
Tables: Made of either wood or concrete.
- Table Height about 75cms.
- Table Width about 120-160cms.
- Table Length about 30-60meters or as long as required.
- Depending on the size of table, table top is inclined to one side about 2.5cms to 25cms.
- Table is covered with 6mm thick woollen felt cloth. Felt Cloth is covered with cotton greigh backing.
- The RFP Fabric is pinned or gummed to the prepared table flat top.
- Guide rails are fixed to the sides of the table to ensure correct registration of colour on RFP fabric.
- Bottom of table is fitted with heating apparatus to dry the print.
Screens: these resemble shallow trays and consist of cloth stretched tightly over and fixed to strong wooden or metal frames.
- One Screen per colour is required.
- Frames for screens are about 15-20cms larger than the design to be printed. Frames are larger both in length and width. This is to facilitate proper and even spreading of print paste.
- Usual frame thickness is 7.5cms(3inches). Usual frame size(outer) is L165cms X W138cms, so it is easy to handle.
- Depending on size of repeat, number of repeats exposed on the screen is limited to fit in within the screen size.
- Sides of the frame are levelled in such a way that when the screen is laid flat on table/fabric, only a minimum area touches the table. This is done to prevent defects in prints caused by the printing screen/frame smudging the already printed area.
- Bolting Cloth – cloth used to make screen: is generally silk fabric tightly stretched by hand or machine on the frame and fixed. Nylon or Polyester bolting cloth may also be used. To get good coverage and an even finish on print surface, fine mesh is used for printing on fine fabric(sheer or light weight or medium weight fabric), coarse mesh is used for printing on coarse fabric(medium weight or heavy weight or bulky).
Squeegees: These are required for applying colour paste to the fabric. These are made of wooden handles and rubber plates. The rubber plates are tapered sections at the bottom so that the edges travel easily and smoothly on the screen. Two workers, one on each side of table use the same squeegee to apply colour paste to fabric.
MANUAL SCREEN PRINTING PROCESS
The colour paste is first poured at the bottom end of the shallow trough of the screen. The colour paste is drawn over the screen from one end to the other end with 2 or 3 up-down strokes of the squeegee with uniform pressure. Uniform pressure of squeegee transfers colour paste evenly to fabric underneath the screen. The screen is lifted and moved to slot 3. Slot 3 is printed and then all odd numbered slots are printed and dried. Then the even numbered slots are printed and dried. Once all slots are printed, the whole fabric is printed as required. To avoid smudging or distortion of printed design, printing is carried out on alternate slots first and later the left over slots are printed.
Each screen is washed immediately after completion of printing with a jet of cold water. As no time the print paste should dry on the screen as dry paste on screen blocks/distorts the design. The screen may break while cleaning the dried print paste.