(to some sample registration of color separations)The following is about registration for offset printing, but the basic ideas are the same for alternative photography processes using several negatives. Negatives can be registered with tape or pins for multiple exposures or layers of sensitizer. Retouching film is the same for all these processes, as is using paper cutouts and spattered ink and so on for alternative forms of negatives .
flat = goldenrod+negative
goldenrod = yellow or orange masking paper
Make any touch ups or additions with red opaque pens, cake opaque, black Sharpie pens, India ink, pieces of rubylith, goldenrod or black paper. Opaque or India ink may be brushed or spattered for different effects. The negative may be scratched with razor blade on the emulsion side to make clear lines which will make dark lines on negative (reversal) plates or light lines on positive (direct) plates. Ink drawings on clear mylar or thin paper, computer printouts or photocopies on clear plastic (transparancies, overheads), paper or rubylith cutouts, all may be used instead of negatives. Paper negatives will need much longer exposures and the paper grain may show up.
Negatives may be combined. Sandwiched negatives will need longer exposures. For pieced together images, cut negatives to fit exactly and tape in unobtrusive spots with tiny pieces of clear tape, to avoid unwanted lines across image. Or, leave big overlaps as part of the design.
No matter what method of registration you are using, tape, pins, or others, you are lining up a spot on the film image with a corresponding spot on the plate. For several plates in register, you are aligning a spot on each plate with corresponding spots on the other plates. Each of these corresponding spots is always the same distance from the registration tape or pin.
Lay out negatives and goldenrod on the light table. Start with goldenrod slightly larger than the plate. Goldenrod scraps may be taped
together for simple rectangular images.
For positive plates, the blank areas need to be exposed, not covered, and negatives can be positioned on clear plastic (mylar) instead of goldenrod. Use tiny pieces of clear tape on the clear plastic so they won't show. On goldenrod, masking tape or any other tape will do.
Take a sheet of goldenrod for each separation. Lay goldenrod and negatives out on the light table.
For pin registration, with all sheets together, punch two holes on one side, corresponding with the top of the plate.
For tape registration, mark where the corner of the first plate lies on the first sheet of goldenrod, and then line up and mark each subsequent sheet with this first one.
Mark actual size of plate on goldenrod for reference and registration, with pencil marks at cor ners, and roughly centering the plate.
Position the negative emulsion side up (wrong way, dull side) on goldenrod. Allow blank space for top edge where the plate will be attached by tape to the press, and for margins on the print. Larger margins for the print may be achieved on the press, but leaving at least an inch or so border on the plate will make printing easier.
The image should be positioned the way it will be in final print. Lettering going the right way on the flat and plate will be the right way on the print. (for lithography, the plate should be the mirror image of the desired final result).
Tape negative in place with a few short strips of masking tape.
Turn goldenrod over, so the negative is facing down, underneath the goldenrod.
Cut out desired image area on goldenrod with razor blade, pressing lightly so negative isn't cut.
Label the flat to avoid confusion (eg."top", "needs longer exposure", "cyan separation")
For next flat, lay a new sheet of goldenrod over inverted first flat, with the negative on the first flat emulsion side up. Line up second goldenrod sheet with holes or corner marks. Lay second negative on second goldenrod emulsion side up, line it up with first negative, tape, turn over, remove first flat, cut out second flat, and retouch. When completed, lay the second flat over the first flat, both right side up with corner marks or pins lined up, to check positions of images. If needed, reposition and retape second negative on second flat.
Make third, fourth flats, etc, the same way, by lining them up with the first flat, and checking registration when done by putting several or all the flats together with the pin holes or corner marks lined up. Label the flats as you go along.
When exposing plates, tape flat to plate to keep everything aligned.
Registration on the offset proof press
On the offset press, make an L-shaped corner of tape on the press bed near the grippers where top edge of printing paper should go. Align each sheet of paper with the tape corner before printing.
If desired, use a large sheet of clear plastic to register multiple plates/colors: Print first color, registering prints with a tape corner. Tape a clear thin plastic sheet to the back end of the press bed and put the other end under the grippers. Mark where its top corners od the plastic reach to on the press bed, with pieces of tape, near the grippers. Print the second color image on the plastic. With the plastic still aligned with tape marks, slide paper printed with first color underneath. Line up image on paper with image on plastic. Once aligned, make L-shaped tape corners on the press bed to mark the printing paper position. Set grippers on paper, pull the plastic sheet back out of way, and print second color. Line up the next sheet of paper with the tape corner mark(s) put down using first sheet. You can also use the plastic for reference and corrections.