Introduction

For my project, I worked with two different intaglio printmaking techniques – etching and aquatint – on copper plates. The purpose of my project was to determine the best mordant (Ferric Chloride or Nitric Acid) for creating certain visual effects (line and tone). The copper plates and a hard ground were my constants, while I varied the acid used as well as the time each plate spent in the acid baths. I measured the effects of the reaction between the acid and the copper visually through making prints. My final goal was to produce a work of printed art to demonstrate my scientific conclusions regarding the etching and aquatint processes.

Background

Aquating and etching are forms of intaglio printmaking. The word intaglio is derived from the Italian word "intagliare," which meants "to carve or cut into." An etching is a type of print that produces lines as acid bites into the parts of the plate that are not covered by an acid resistant ground. The aquatint method is used to create tonal effects from the acid biting into open areas not covered by either rosin or spray paint and received its name from the Latin word "aquafortis," meaning "strong water," and the Italian word "tinto," which means "tone."

Surprisingly, the history of printmaking did not begin with the invention of the printing press. There are, in fact, records of engravings made 3,000 years ago from bone on carved into cave walls. Printmaking, initially only used as a way to communicate, was not actually considered an art form until the late eighteenth century. The art of printmaking has been developed through the years, and using Ferric Chloride to etch Copper plates is actually a newer technique than using Nitric Acid as the mordant, which is why I chose to compare the effects these two etchants have on Copper plates.

HYPOTHESIS: Before I began this project, I hypothesized that the Ferric Chloride would produce a more controlled line than the Nitric Acid. I had never worked with Ferric Chloride before, but I had worked with Nitric Acid (on zinc plates, though) in a previous lab this semester.

Procedure

Materials:

Copper Plates
Putz Pomade
Steel Wool
Paper Towels
Mineral Spirits
Isopropyl Alcohol
Stop Out Varnish
Hard Ground
Stylus
3 Molar Nitric Acid
5.2 Molar Nitric Acid
Ferric Chloride
Tweezers
Acid Trays (large enough to fit plates)
Timer
Goggles and Rubber Gloves
Rosin
Hotplate
Charbonelle Paint: Van Dyck Brown, Ultramarine Blue, Black
Paper
Press

Part One: Preparing Plates

1. To clean the plates, apply Putz Pomade with steel wool (strong circular motions work best) to the face of the plate on which the etching will take place.
2. Rubbing the plate with a paper towel covered in mineral spirits between Putz Pomade application expedites the cleaning process.
3. Once the plate is clean, spray the backside of the plate with a coat of spray paint to keep that side of the plate from reacting with the acid.
4. Rub the face of the plate that is going to be etched once more with mineral spirits and then alcohol to ensure cleanliness.

Part Two: Etching Lines with Nitric Acid and Ferric Chloride

NOTE: All work with acids should take place under the hood. Goggles must be on at all times; wearing rubber gloves is suggested. Also, observations should be recorded throughout the entire experiment.

1. Create a test plate using 3 molar Nitric Acid:
1. Use a paint brush to apply an even coating of hard ground to the face of the plate.
2. When the ground is dry, use a stylus to scratch lines on the left side of the plate into the ground. Scratch only deep enough to expose the copper plate; do not scratch the plate itself.
3. Prepare an acid bath: pour enough of the Nitric Acid in a plastic container so that the plate can be fully submerged.
4. Place the plate in the acid for 3 minutes. Use tweezers to remove it.
5. Using a paint brush, cover one third of the plate with Stop Out Varnish. Repeat two more times.
6. Use mineral spirits to clean the ground and varnish off of the plate.
2. Create a second test plate using 3 molar Nitric Acid:
1. Follow same steps as above, but on the other side (on the same face) of the plate for three ten minute time increments.
3. Create a test plate using 5.3 molar Nitric Acid:
1. Make a more concentrated solution of nitric acid by mixing 100ml of acid with 200ml of water.
2. Prepare a new acid bath.
3. Repeat the previously stated test plate procedure on a new plate, this time with three five minute intervals.
4. Create a second test plate using 5.3 molar Nitric Acid:
1. Repeat same procedure as above on a new plate with 15, 25, and 35 minute time intervals.
5. Create a test plate using Ferric Chloride:
1. Prepare a new bath with Ferric Chloride.
2. Follow the steps for creating a test plate using 5, 10, and 15 minute intervals.

Part Three: Making Prints of Etched Lines

1. Soak the paper that the print will be on in a bath of water for at least 15 minutes.
2. Prepare a template by tracing the size of the paper and the plate onto another piece of paper.
3. Prepare Ink: mix Carbonelle Van Dyck Brown ink
4. Apply ink to plate using small pieces of cardboard. Cover entire plate, and make sure ink goes into the etched grooves.
5. Wipe off excess ink with another piece of cardboard, and then use clean pieces of newspaper. Make sure ink stays in the grooves.
6. Clean hands. Remove soaking paper from the water bath and blot dry. The paper should be moist, not wet.
7. Place inked plate face up on the template on the press. Place moist paper on top of the plate and cover with scrap paper. Place the felts down one at a time.
8. Run the plate and paper through the press with the setting on 11. Lift the felts one at a time and remove print.
9. Clean the plate using mineral spirits and alcohol.

Part Four: Using Aquatint to Experiment With Tone

1. Create an Aquatint test plate using Ferric Chloride and spray paint:
1. Evenly spray the face of a plate with paint. Wait for it to dry.
2. Hold onto the plate using tweezers and gradually submerge it into the Ferric Chloride bath every 20 seconds for one minute.
2. Create another Aquatint test plate with Ferric Chloride following the same steps as above, but with 1, 2, and 3 minute intervals.
3. Create another Aquatint plate, but this time use mineral spirits to clean off the spray paint around the edges to create a drastic difference in tone. Submerge the plate for 15 minutes.
4. Create an Aquatint test plate using rosin:
1. Place about a handful’s amount of rosin on three layers of cheesecloth. Fasten the cheesecloth with a rubber band, so it looks like a bag.
2. Evenly distribute the rosin onto a copper plate.
3. Place the plate on a hot plate; wait for the rosin to melt and adhere to the plate.
4. Once cooled, put plate in bath with 1, 3, 7, 15, and 31 minute intervals. Use hard ground to block out the parts of the plate that no longer need to be etched. 
5. Remove the rosin and ground with mineral spirits and alcohol.
6. Follow the same steps as followed with printing etchings to print the aquatint plates.

Part Five: Using Conclusions to Create a Work of Art

1. Etch a design made with lines into a plate using acid of choice (I chose Ferric Chloride). The plate should be submerged for the amount of time that worked best according to the test plates (I decided on 15 minutes).
2. Clean plate.
3. Use best method and time for aquatint. (I chose to use the rosin method in a bath of 6m Nitric Acid.) Use hard ground to experiment with tone. (On my plate I had parts that were in the acid for an additional one or two minutes. Some places were blocked off completely and had no tone. I made small test prints after each time interval.)
4. Make prints!

Observations and Data

Etching Lines With Nitric Acid:

Etching Lines With Ferric Chloride:

Plate	In Acid	Plate	Print
Ferric Chloride Test Plate	The Ferric Chloride is a dark yellow color, which makes it very difficult to notice any reactions occurring while the plate is in the bath.		I made two prints of this plate; the first did not turn out at all, probably because the paper was too wet. The second print, however, turned out well. As time increases, the line becomes darker, but does not increase in thickness like it did in the Nitric Acid solution. The part of the plate that was in the acid for fifteen minutes looks the best out of everything tested.

Exploring Aquatint Using Ferric Chloride:

Plate	Preparation	In Acid	Plate	Print
Aquatint Test Strip 1	I used spray paint as the method for this plate.	no visible reactions	There is no visible difference in tone among the different sections of the plate.	No visible difference in tone. One minute is probably not long enough, so I decided to make another test strip. There is also a yellowish tint on part of the print.
Aquatint Test Strip 2	I used spray paint as the method for this plate, and am noticing that it is very difficult to create an even tone across the plate with the paint.	no visible reactions	There is only a slight difference in tone among the different sections of the plate.	No visible difference in tone where it should be. There are darker sploches throughout the middle of the print, but these have nothing to do with the amount of time spent in the acid. Three minutes is probably still too short, so I decided to do another test strip.
Aquatint Plate	I used spray paint for this plate.	no visible reactions		This print turned out well. There is a very significant difference in tone. The acid bit well into the plate over the fifteen minute period.
Aquatint Test Strip 3	The spray paint was not working well, so I decided to use rosin, which I found to be much easier to control. When I heated the plate the rosin became more red than yellow.	no visible reactions	It is easy to see the difference in tone among the different sections of the plate, especially between 7 and 15 minutes.	The rosin works much better than the spray paint. The test strip turned out well. The most significant difference is between 7 and 15 minutes.

Creating a Work of Art:

Conclusions

Through my experiment, I found that the plates etched in the Ferric Chloride solution for fifteen minutes produced the best (most controlled, while still dark) lines. Looking at the image above, this conclusion is obvious. The print to the left was etched with Ferric Chloride. It’s lines are much more aesthetically appealing than those created by Nitric Acid, plus they hold ink much better without being as fuzzy. Furthermore, it took less than half the amount of time for the Ferric Chloride to etch these lines than it did for the Nitric Acid. Chemically, I know that the ferrous ions from the Ferric Chloride solution react with the solid copper, and it is this reaction that causes the copper to be oxidized to form cupric ions, thus creating the "bite" into the copper:
The two half reactions:
            2 Fe³⁺  +   2 e^-  → 2 Fe²⁺   
                        and
            Cu (0) → Cu²⁺  +   2 e^- 
form the whole reaction:
          2 Fe³⁺ + Cu (0) → 2 Fe²⁺   + Cu²⁺ 
* The Copper loses electrons and is therefore oxidized, which visually appears as the acid biting into the plate.

Both acids produced aesthetically pleasing aquatints, but I found the 6 molar Nitric Acid combined with the rosin method to be the most efficient way to produce tonal effects. The rosin is much easier to control than the spray paint and the Nitric Acid bites into the copper much faster than the Ferric Chloride. Like when the Ferric Chloride reacted with the Copper, the Nitric Acid also causes the the Copper to be oxidized from 0 to +2, which is evident in the equation: 3Cu + 8HNO3 --> 3Cu (NO3)2 + 2NO + 4H2O

Throughout the course of this project I found myself dealing with artistic obstacles that got in the way of my scientific experiment. The possibility for human error is very high in printmaking, but I have learned that sometimes errors lead to more interesting prints! Despite my many errors, however, I did find my hypothesis to be correct, and I did stick to my original plan, which was to create a work of art encompassing all that I had learned about the etching and aquatint processes. I was happy to find a use for both acids in my final work of art, which proves the point that each acid bites into the plates differently, and therefore creates unique effects, which is what I was hoping to conclude from this project.

Links

http://artmondo.net/printworks/articles/ferric.htm

http://www.sewanee.edu/chem/Chem&Art/default.html

http://science.jrank.org/pages/2515/Engraving-Etching-Origins-history-intaglio-printing.html

Other References

Ross, John, Clare Romano, and Tim Ross. The Complete Printmaker: Techniques, Traditions, Innovations. The Free Press; 1990.

Acknowledgements

I would like to thank Ms. Carolyn Fitz for all of her help. Without her printmaking knowledge and extreme patience, this project would not have been possible!