Fig. D: Expose the coated metal plate for 4 minutes
under a 500W photoflood lamp, with the reflector positioned 18" above. Don’t worry if the reflector isn’t rated
for a bulb that hot; it isn’t on for long enough to matter.
over the coated surface for 45 seconds.
3. Remove the object from the dish, draining
developer back into the dish.
4. Place the object into Pyrex dish #2, and pour
in enough new, fresh ER- 8 to just cover the
surface. The exposed coating is very soft and
delicate at this point.
5. Very gently rock the dish for 10 seconds.
Lift the object out of the dish and let it drain,
handling it only by the edges.
6. The coating is now no longer light-sensitive,
but it is invisible and extremely delicate until
it’s dry. Do not touch! Set the object aside to
dry fully, for 1 hour.
NOTE: ER- 8 developer is reusable an unknown
number of times, probably a dozen or more.
The second brief dip in fresh ER- 8 just rinses off
any crud that was in the used ER- 8 from the
main step. This stretches the life of the developer.
I keep my used ER- 8 in a clean glass jar.
Find and Fix Flaws in the Coating
If the exposure process failed, etching will just
roughen the plate’s surface and you’ll have to
sand it all off and start over. Here’s how to make
126 Make: Volume 09
Fig. E: During exposure, the transparency should be
positioned with its inked side directly against the
metal, pressed down with a plate of glass.
the coating pattern visible; then check it and
correct any flaws before etching.
1. Fill a Pyrex dish with water and add just a few
drops of etchant.
2. Immerse the plate in the dish; the coated areas
will remain shiny while the open areas will faintly
etch, making the coating pattern visible.
3. Compare the coating pattern to your original
artwork and look for areas where the plate should
be etched, but are still shiny (coated), and vice
versa. For areas that should be etched but weren’t,
use a knife to carefully scrape the coating away.
For areas that should be coated but are exposed,
cover them using a paint pen or pieces of tape
trimmed to shape. Correcting a few flaws this
way is fine, but if large portions of your design
didn’t make it through, you’re better off repolishing the plate and starting over.
4. You can discard this very weak etchant solution
by pouring it down the drain and following it with
copious amounts of water.
Etch the Metal
This step completes the process. The ferric
chloride etchant eats away metal from the object
anywhere that coating was not exposed to light.