perm filename PHOTO[EMS,LCS]1 blob
sn#197645 filedate 1976-01-21 generic text, type T, neo UTF8
PHOTO ETCHING INSTRUCTIONS
Edith Smith, Instructor
I. Cut photo-plate to size desired. Re-tape remainder and projected plate.
II. Film Preparation:
Film is prepared for exposure onto Revere photo-sensitive zinc plate.
Kodalith 3 film may be shot in the darkroom. For intaglio processes, a film
POSITIVE is made, always using a half-tone screen. A 133 dot screen is preferred.
Test strips should be shot through strategic lights, half-tones and darks at
exposures from 45 to 75 seconds. Not only do you want the exposure that does
most for your particular image, but you want one that will carry a clear dot
pattern in the blacks. This is one of the most important considerations in
photo intaglio work. After longest test exposure, a 20 to 25 second "flash"
is recommended -- with negative removed from carrier and enlarger raised all
the way up. This is to insure a dot pattern in blacks (to hold ink in the
darkest areas). Check you test strip results with a magnifying glass. When
you've decided on correct exposure time and flash time, shoot your plate-sized
Kodalith positive(s). For relief printing on zinc, a Kodalith negative is used,
and no half-tone screen is necessary. For grainy silk-screen-like prints, you
should use this method. I prefer a 1 part H2O, 1 part A and 1 part B developer
to the usual stronger mixture. Thus, your image will come up slower and you
have more control.
After you finish with your darkroom work, you will probably want to
modify your Kodalith through any one of many creative techniques. You may
wish to cut the film(s) up into a collage or overlay (double image). You may
wish to scrape away large or small sections with a knife or etching needle.
You may wish to add blacks with brush or pen and ink (non-crawl acetate ink
or India ink) -- or with litho crayons or pencils. You may wish to turn certain
areas into cloud-like, vaporous half-tones by applying a 50% clorox, 50% H2O
solution with cotton. Precise white lines are created in your intaglio print
by scratching white lines out of inked or exposed film areas.
If you are drawing directly on film, without using a photographic
negative, utilize .005 or .007 acetate. This may be collaged or overlaid
also. But remember to test overlays carefully for longer exposure. Any
drawing techniques just discussed may be used on acetate, plus any you think
just MIGHT work. Film, either singly or in collage or overlay must be the
same size as your intended photo plate in total dimension. Remember, the
image you see UP, as you lay the film on top of your plate for exposure, will
be MIRRORED in your final print. Hence all writing, lettering, etc. should
be BACKWARDS (emulsion side down) during exposure.
Before exposure, pour Revere Developer into a metal or glass tray.
Don't use rubber or composition tray. Use well-ventilated area.
III. Exposure:
Make sure glass you place over your film and plate is cleaned with
ammonia and is free of scratches over image. Set lamp 18" above glass.
Cover glass with plywood for one minute as lamp heats up (this is to give
full play to ultra-violet). Then try a series of test exposures across
strategic parts of your film. No effect is possible at under 3 minutes.
Beginning exposure over-all is 3 1/2 minutes. Moving board or cardboard
over plate, gradually close down the exposed area every 30 seconds, till
the last strip of the test strip has received about 7 1/2 or 8 minutes
exposure. Most work needs a plate exposure of about 4 1/2 - 5 1/2 minutes.
For all-drawn work, or for Kodalith WITHOUT half-tone screen, about 5
minutes is recommended.
IV. Plate Development and Wash-Out:
Procedure for test strips and real plate is exactly the same. With-
out touching top of plate, carry plate to developer. Submerge photo-plate
with the same motion you use to enter film into a developer. Exposure
time is 2 1/2 minutes (unless developer is very old.) Agitate gently but
continuously. The care with which you handle the plate when lifting it
from the developer and until it is completely "set" after several minutes
of water wash-out is crucial. This is the crucial time of the whole
process because at this time the resist is soft and jelly-like. Don't
touch top! Let plate drip in sink for one full minute. Then, with a
VERY SOFT stream of COLD H2O, begin wash-out, keeping plate tilted at
a sever angle to the stream. After about 2 minutes you can increase the
amount of water in stream. Wash-out should last 4 minutes.
Set plate up leaning against a wall on top of a clean counter
or table for 1/2 hour. Funnel your developer into re-cycling drum
immediately. Have another student hold funnel. Clean hands thoroughly.
V. Hand Work and Acid Baths:
1. Intaglio plates with half-tone screen should probably be bitten
10 to 12 minutes, depending on acid strength. Open bite. Then if there
are some black areas that haven't received a dot pattern, the "tooth" to
hold the ink in these spots must be supplied by aquatint (or drypoint, if
problem area is small). Although rosin aquatint MAY be used, plastic spray
is preferred. Bite plate 4-8 minutes more, depending on bath strength
(5 minutes average).
2. Plates that are to be bitten for rolled relief printing should
probably be bitten down at least an hour. Color viscosity biting can also
be tackled at this point, if desired. However, any section of plate defined
by a screen should probably not be bitten longer than an hour; undercutting
could destroy the pattern.
3. ANY kind of plate modification or etching or drypoint technique
may be utilized either before first bath or at any later stage. Drypoint
through the blue photo resist is beautiful. Needled, etched lines may be
added at any time. The resist may be removed wholly or in part with acetone.
A vaporous effect, unequalled in any other phase of etching, is achieved by
dragging an acetone-soaked rag over plate and eliminating resist selectively.
Any length of bath follows, depending on effect desired. Liquid ground can
form new resist patterns once photo-resist is removed. New aquatinted shapes
can be created in counterpoint with the original photo half-tone if resist is
partly or wholly removed. Taped hard-edges can be created over photo-image
before or after initial bath. Whole new areas can be scraped or bitten: these
practices are particularly applicable if several photo-plates are to be used
in registration; the concept of "dropping out colors" applies.