Experimenting with the saline-sulfate etch.

Home  >>  Tiger Lily Press  >>  Experimenting with the saline-sulfate etch.

Since Tiger Lily Press
 will be moving towards being a more “green”
printmaking studio once our move is finalized, it was finally
time to start experimenting with some alternative & safer
etching techniques.
So a small group of us met at
the studio today to experiment with
the saline-sulfate method for
etching zinc plates.
Being an “old-school” printmaker, I was mildly
suspicious of using anything but
nitric acid to etch zinc!
To begin with, equal parts of common table salt
and copper-sulfate are mixed together. Since I was
only mixing enough for a small tray,
 I used 3.5 oz. of each.
Added to that is 2 cups
of hot water, stirring until 
the mixture has dissolved.
(the solution begins as a murky
blue-green, and turns a clear green
as the crystals dissolve)
This was added to the etching tray and 
an additional four cups of hot water
were added to further dilute it.
This made for a somewhat “hot” bath.
In the future I may try diluting with an extra
one or two cups of water and experiment again.
A weaker solution will probably work
more effectively with delicate
processes such as aquatint.
Immediately upon placing a coated plate into the solution,
the exposed zinc turns black and begins to 
throw off a lot of copper colored sediment.
It was quickly apparent that the plate and/or
tray would need to be agitated to keep
the sediment from effecting the etching process.
Below are my two printed test plates. The first is a 
hard-ground coated plate with line work
etched in increments. Beginning at 5 minutes,
ending with a 20 minute etch. Since the acid
was stronger than I expected, I wish that I had started
with a one minute etch.
The second print is aquatint, etched in 15 second increments.
The darkest square, on the right, was etched for 1.5 minutes.

Elaine’s test plate being printed by Brian. She used hard
ground, scratched off the plate, and then 
coated with a spray paint aquatint.  It was
etched for approximately 25 minutes.
(her plate can be seen in the tray in photo #4)
Brian tried several test plates with aquatint. Notice how 
much crud is on his plate in this first photo! This plate was 
etched up to seven minutes for the darkest tone.
For this plate, the rosin was applied by
using a rosin dust bag for a grainy effect.
Sections were blocked out with
stop-out varnish and (if I remember correctly), the plate
was etched in several increments for
up to five minutes.
The last experiment of the day was an open bite, etched 
just for a minute or two. At this point the acid
has become a mess!
The 2nd photo shows how the plate turns
black when exposed to the acid.

I don’t have a photo of this plate printed,
but there was enough “tooth” to the etched area
to print a pale grey tone.
We carefully poured the remaining solution
into a plastic jug to save, leaving the sediment
in the tray.

So in conclusion, this “old-school” printmaker
is most likely a convert to this technique. It definitely
worked better than I expected!

For a downloadable PDF file on the technique, click here

Visit the nontoxicprint website for 
more info on safer printmaking options.


5 Comments so far:

  1. Ken Swinson says:

    This is exciting! Glad to see the eco friendly techniques are a success.

  2. Anonymous says:

    Great post Rick!!! Excited to see more…

  3. Great documentation I just switched over from Ferric myself. I've mixed the dry chems but haven't started etching yet. Nice to see some results as I was a little skeptical as well. From my notes It was 1/4 the amount of copper sulfate to salt. so for my etch tank at 15 liters it would be 1kg of salt 250gs of copper sulfate and 25gs of sodium bisulfate. But I'm starting to etch aluminum right now. Is it recommended to bump the copper ratio that high for zinc? Just curious.

  4. Mark, I've never etched on aluminum, so I don't know how that process works. I followed the instructions from nontoxicprints.com. Their recommendation was equal amounts of copper & salt. I felt that was really a strong bath for zinc, especially for aquatint. I think a more diluted bath would be better for fine line work and delicate aquatints. Overall, I think it works pretty well, just requires more work to get it right.

  5. Nik Semenoff says:

    What you printers seem to be missing is one of the great advantage to using various methods of using modified copper sulfate on all etching metals – is that it will regenerate itself with access to oxygen. You find it on my websites as well as Alfons's comments on this forum.

    Nik Semenoff