Again a couple of weeks has passed on the screen printing, so I am recording details of the various stages to help future attemps.
The screen is attached to a small printing set up (the paper on the underside of the screen was only needed as this screen extended further than the other two separations). When the screen is lowered, it activates a vacuum pump that ensures contact between screen and paper during printing. The area of the vacuum bed that is not cover by the screen print is masked off with newsprint. Registration marks are placed on the bed so that each piece of paper is identically placed (nb make sure paper has exact corners). The first separation is then printed - I chose a transparent mid blue for the first screen. The ink is dragged across the screen by pulling the squeegee at 45 degrees to the screen. The screen is lifted and then the print area is flooded with ink by pushing the squeegee back.
To print the subsequent screens, it is necessary to align the registration marks correctly. To do this, tape down a piece of clean film over one of the orginal prints and print onto this. Then move paper around under the acetate till it is exactly in register and place the registration marks. Remove acetate.
I printed the second screen first all over with a transparent dark blue. Some work was then done with the blue filler to cover the nearest tree trunks and branches and with bleach to open up the sky ares. I then chose a transparent very diluted black (using 1 to 5 parts of black to extender) for the sky area (masked off the trees) and a more opaque grey (diluted white with extender) for the back trees and tops of branches.
All it needs now is the third (black separation) screen.