Screen Preparation

TechShop:Screen Preparation

Guide

Stretching a screen

Screens can be stretched manually, using a staple gun (if they are wooden) or using the screen stretcher. For this project, manual stretching will be used to make a screen.

Manual Stretching

  1. Mesh should be cut to about 5cm larger than the outside of the frame.
  2. Start in the centre of one of the longer edges of the frame, and staple the mesh in place putting the staples on the side edge (not the face) of the frame. Put the staples about 4cm apart and at an angle of 45 degrees. This is the most stable and is less likely to tear the mesh. Complete the side, working outwards in both directions
  3. On the opposite side, starting in the middle, pull the mesh across as tightly as possible, keeping the grain straight. Staple in place and complete the side, working outwards in both directions in the same way as the first side.
  4. Repeat the process with the remaining two sides keeping the fabric grain straight. On the third side, do not pull the mesh tightly across the centre of the screen and distort the grain, but the fourth side needs pulling as tightly as possible.
  5. Fold the corners neatly, and staple down.

Coating a Screen

Photographic emulsion comes in two parts: an emulsion and a sensitizer. Once these are combined, the mixture is light sensitive, and is kept in a darkened room. After mixing, the emulsion should be left for half an hour before coating a screen to allow the air bubbles to come to the surface as these can cause pinholes. The emulsion available in the Exposing Room has already been sensitized.

DO NOT REMOVE YOUR SCREEN AT ANY POINT FROM THE EXPOSING ROOM BEFORE IT HAS BEEN EXPOSED!

  1. Choose a trough that fits inside the frame of the screen and fill with emulsion. Get someone to hold it for you while you coat it.
  2. Start at the bottom, on the outside of the frame, and hold the front edge of the trough against the mesh, tipping the trough until the emulsion meets the mesh.
  3. Move the trough firmly up the screen, keeping at the same angle all the way up thus providing an even coating.
  4. Return to the bottom of the screen, move the trough up but do not tilt it forwards so that the excess coating is removed.
  5. Before putting in the drying cabinet, outside of screen upwards, check it is evenly coated and there are no thick areas. If necessary, remove more emulsion. Try to avoid excessive coating or scraping as this will increase the likelihood of pinholes.
  6. Put excess coating back into the container, wash the trough then hang back above the sink.
  7. Dry for a minimum of 3 hours before exposing. Screens can be left in the drying cabinet overnight prior to exposure.

WIPE UP ANY SCREEN COATING YOU MAY HAVE INADVERTANTLY SPILLED.

Notes:

  1. If the screen is coated very unevenly it is possible to coat the other side by repeating steps 2-4 on the other side of the screen, but this will always be more inferior.
  2. Do not coat screens then put above others in the cabinet – move them up and put yours below.
  3. Do not put washed, wet screens to dry in the drying cabinets in the exposing room.

Exposing a Screen

  1. Stick the image on the outside of the screen with sellotape, the drawn side of the image against the mesh.
  2. Put the screen, image side down, onto the glass of the exposing cabinet and lower the lid.
  3. Switch on ‘mains’ then ‘pump’ and do up the clamps until a vacuum forms.
  4. PUT UV GLASSES ON, then switch both light switches on for a minimum of 2 minutes. Use the clock behind the machine to time the exposure.
  5. Switch off lights, undo clamps, switch off ‘pump’, switch off ‘mains’ and remove screen from unit once vacuum has gone.

IMPORTANT: make sure the machine is completely switched off and UV glasses are back in the holder before leaving this area.

Washing out a screen

  1. Remove the sellotaped image then gently wet both sides of the screen, and continue washing from the inside until the image appears clear. Hold it up to the light and look through it to ensure that the image is unblocked.
  2. Keep washing until any residue of loose coating has gone and the surface no longer feels slimy. If this is not removed, it may temporarily block the print.
  3. Gumstrip the screen on both sides and leave to dry.

Touching up a screen

Before the design is printed, check for pinholes or other incidental marks that require patching. Hold up the screen to the light or check it on a lightbox. The most immediate way of doing this is with tape on the back of the screen, but this is temporary and needs rechecking every time the screen is washed. It is better to use the screen coating to paint onto the outside of the screen where required. This can be done on a light box or against a light source (e.g. window) and left to dry in the light. The screen is then ready for use; it does not need washing out.

Steps to create to complete the workshop as required.

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