|Copper sulphate etching on found beer can. Hahnemuhle cotton watercolour paper Akua ink. Diana Parkhouse 2022. |
Copper sulphate (sulfate in US) solution etching of aluminium (aluminum US) for printmaking is an accessible entry point to metal plate etching. The copper sulphate solution is easily stored at home and requires no special tanks or exhaust equipment to use. It is still a corrosive and should be treated with care and respect, however with a sensible approach many adult print makers wanting to start out in etching metal plates will find the etching of aluminium with copper sulphate a great place to start.
This article will focus heavily on methods of using aluminium drink cans as the source material for etching. In my own art practice I am mindful of the environmental impact of my hobby and the path I allow it to take me down. Where I live aluminium drink cans are frequently discarded as litter by people and I collect them and use them as a free source of aluminium for my art practice. Even after etching aluminium can 'plates' can be recycled in the domestic recycling collection.
How it works - a basic overview
Aluminium can be etched (corroded) by a copper sulphate solution mix of copper sulphate, salt and water. Aluminium drink cans have a polyethylene (plastic) coating on the inside which when used in this printing method protects the aluminium from the copper sulphate solution. With the action of scratching the plastic coating away to reveal the aluminium, the marks made with the the plastic removal will be etched when exposed to the copper sulphate solution. These etched marks hold printing ink and prints can be made on paper in the intaglio method.
Aluminium drink can etching step-by-step
Start with a clean rinsed dry aluminium drink can. Any aluminium drink can will do; soft drink, beer, energy drink. It doesn't matter. They are all coated on the inside with a polyethylene (plastic) coating. This is a great ready-made resist to scratch away and reveal the aluminium design which will be etched to hold printing ink.
Carefully cut the can open so that the ends are removed and the aluminium becomes a single sheet. This is sometimes easier said than done. Wear gardening gloves if you feel you may otherwise cut yourself on the aluminium.
Once the can has been cut open, it needs to be manually manipulated until it is a flat sheet of metal. To do this it needs to be pulled in the opposite direction of the curve against the edge of a table or other firm edged surface. Do not do this against valuable furniture, the process will damage the antique Chippendale.
Now is a great time to straighten the edges of the plate as the overall shape of the plate will be visible when it is printed. It is possible to make the plate shape whatever you want it to be. It doesn't have to be a rectangle. It can be square, round, or a more organic shape such as a leaf, tree or cloud. Make it whatever shape you would like to incorporate into your overall design. Give the inside surface of the can a wipe with a damp cloth to ensure that it is clean. It is now ready for the next steps.
|Aluminium can etching. Hahnemühle cotton paper. Akua ink. 'Under a Tree' Diana Parkhouse 2021|
How you proceed from here will be dictated by the kind of result you desire. At this stage it is possible to go in several different directions.
Method 1 - remove the plastic coating completely
Scratching through the plastic can be problematic in having as much mark making control as some artists might like. Removing the plastic coating completely gives the artist an opportunity to replace it with a more preferable ground to work with, such as B.I.G. (Baldwins etching ground), or charbonnel.
Mark making through an applied ground is easier on tools and you have more control over the marks you make.
Removing the coating is possible with the use of fine grade wire wool and a lot of elbow grease. Do not use sandpaper of any grade, it is too coarse and marks the aluminium, unless you desire that as mark making method, which could be a legitimate choice. Tip: wear gloves. The wire wool is hard on the fingers.
Removing the plastic coating is also required for the permanent marker (eg Sharpie) resist method, which is how the piece 'Under a Tree' (above) was achieved. Once the plastic coating is removed, the design is drawn on with permanent marker. The copper sulphate will etch the can wherever there is NO permanent marker. If the design incorporates writing, it needs to be written in reverse (mirror). When printed the design flips and the writing will then be facing the right way. Getting it wrong can be upsetting.
Method 2 - scratch through the plastic coating
Choosing this method saves time on one hand, but on the other hand it can be harder on tools because the plastic coating is harder to scratch through. It is also less exact. If these things do not bother you, or you desire the scratch method outcome, go ahead and save time. Life is short.
The kinds of tools you will need to scratch through the plastic coating fall into the sharp and hard category. Metal scribes, broken craft knives, inexpensive woodcutting tools or a dedicated drypoint needle are all great tools for this method. Experiment with what you have available to you. There are also small mains powered or battery operated engravers with various nibs available that will mark through the plastic coating. I have one that I picked up at a local homewares store to before I even started etching metal because it was cheap and I run on instinct, chocolate and tea.
Transferring your sketch
When working with a sketch that needs to be transferred to the can, options are limited. Through trial and error I've found the application of a thin layer of acrylic gesso to be one of the best ways to make a successful base for a pencil sketch to be transferred via tracing paper. Gesso can only really be applied ahead of method 2. For method 1 BIG etching ground already takes graphite pencil so gesso isn't needed. But for the sharpie method or the charbonnel method, gesso can't be used and are best suited for direct application of the design free-hand.
If using gesso for method 2, brush on a thin coat all over the design area, then lightly roll smooth with a foam roller. Leave to dry completely. After the gesso is dry a graphite pencil sketch can be successfully transferred using tracing paper.
And of course you do not have to apply gesso for method 2 at all if you desire to free-hand sketch using a Sharpie as a guide where to scratch away the plastic.
For any method always remember your design needs to be reversed as the plate is flipped to be printed, as in almost all printmaking methods such as linocut, monotype, etc.
Scratch out your design
For any method the point of the exercise is to expose bare aluminium that can then be etched with the Copper sulphate solution. Any bare aluminium will be etched. Any covered aluminium will not. For method 1 the applied ground needs to be scratched away to expose the aluminium. For method 2 the gesso (if you have used it) and plastic needs to be scratched away.
A note on the Sharpie resist method
After removing the plastic coating with wire wool, permanent marker (Sharpie or similar) can be used as the resist. Where the marker is applied the Copper sulphate will not etch. The Sharpie method has some drawbacks in that no matter how carefully applied, some of the Sharpie will have a thinness of application which the Copper sulphate can etch through.
Etching in the Copper Sulphate solution
Come time to etch the aluminium drink can plate, all care needs to be taken with the use of the copper sulphate solution (recipe at the end of this article). When aluminium is immersed in copper sulphate solution it makes a nominal amount of relatively harmless hydrogen bubbles where the aluminium comes into contact with the solution. Unlike many etching chemicals the copper sulphate solution is relatively safe to use in a household environment so long as care is taken.
- Keep it out of reach of children, pets and vulnerable adults.
- Store it in a plastic bottle that can smash if dropped.
- Do not let children use it unsupervised.
- Wear gloves when handling. If it comes into contact with skin, rinse immediately.
- Do not get it in eyes!
- Do not drink it!
- When etching, don't stand over it and breath it in.
- NEVER POUR IT DOWN THE SINK OR DRAIN.
It won't kill you when used properly; it won't even harm you. But it will seriously hurt a pet if they drink it. And if poured down the drain it will kill all aquatic life it comes into contact with.
To etch the aluminium can
Pour the required amount of solution into a plastic or ceramic dish big enough to fit the aluminium plate when it is laying flat.
Aluminium cans etch fast, especially if the etching solution is fresh. Any longer than 2 mins 30 seconds will see the lines etch right through the can and it will fall apart.
It is possible to wash off the acrylic gesso before etching or after etching. Because I sometimes do a multi-step etch that requires further work on the plate, I am in the habit of washing the gesso off after the final etch.
Insert the plate and start the timer. GENTLY agitating the solution with gloved fingers or a wooden or plastic stick makes the aluminium etch a little faster. This can be handy for etching solution that has been used a few times.
Wearing gloves, remove the plate from the solution when the time is up and let as much solution drip off as possible. Rinse in A LOT of water. Micro amounts of solution in litres of water will not harm the environment. In some parts of the world using litres of water for a hobby might not be ethical. Take this into consideration if you need to, and perhaps use household grey water for this step.
Making a print
Copper sulphate of aluminium is an intaglio print method. Intaglio printing relies on the ink being forced into damp paper with a large amount of pressure. Traditionally with is done with a dedicated etching press, but there are alternatives for artists who do not have access to one. One such alternative is called a cold press (or roll) laminator and is s piece of equipment from the business world repurposed for use by artists as a lino, woodblock or intaglio press. They all look like a bit like this:
|A cold press (also called a cold roll) laminator|
It is also possible to make an intaglio print with a caster wheel like you would find on an office chair. If using this method care needs to be taken to prevent any movement between the plate and paper as this will affect the print result. Bulldog clips or similar can be used to keep this from happening. Thinner papers are also best for the caster wheel method.
Paper needs to be damp and blotted to remove the surface water. Depending on the paper it should be soaked in clean water for anything from 5 to 30 minutes. No one can tell you how long it needs to be for your paper and method. Experimenting is needed.
Which printing ink to use is personal choice. Not all brands are available in all countries so just use what is available to you. Wiping ink into an aluminium can etching is done in the same way ink is wiped onto any intaglio plate. Methods include with a small square of firm cardboard, with an old store card or credit card, or even with a finger.
Wiping the ink away from the plate can be done with newspaper scrunched to form a pad which is how I do it. It can also be done however you have always done it. It is not an exact science and there are many and varied ink on ink off methods for intaglio.
Once the plate is inked and ready it is time to print it. All kinds of paper can be used for intaglio printing, from dedicated quality artist printing papers right through to easy to find smooth cartridge paper. High quality paper does not necessarily result in a good print. Steer clear of rough textured papers as results are almost always poor.
Copper sulphate etching solution recipe
- 100 grams copper sulphate (I bought it online)
- 100 grams table salt,
- 1 litre of water
- ALWAYS wear rubber gloves and eye protection when handling this solution.
- Do not smell the solution, stand over it or breath it in.
- It eats away at most metals so you need to keep it in a PLASTIC bottle (not glass because it will smash if dropped by accident) away from pets and children, and etching needs to be done in a plastic, ceramic or glass container.
- Never use near children, or pets eg where a cat can jump up on the table.
- IT WILL BURN. Rinse your skin immediately and seek medical advice if you get any on you at all.
- Immediately after you use it do not leave it laying around in the bowl or tub. Wearing gloves etc, and using a plastic funnel, transfer it carefully back to the plastic bottle, put the cap on, and put it away asap. Rinse the bowl with a lot of water.
- DO NOT POUR IT DOWN THE SINK OR DRAIN