Etching roofing zinc with copper sulphate

Etch your own zinc printing plates at home

Traditionally the etching of metal printing plates involved heavy duty acids – this meant the process was dangerous, and not a practical thing to do at home. Happily, it is now possible to etch your own plates at home without acid – by using copper sulphate.

I have been experimenting with this because I wanted to find ways to convert a photograph into a printing plate for my ‘Eve’s footprints’ series. I am really pleased with the results, although at present mine are just black and white – half tones will need more practice!

Here is the story of Eves footprints, copper sulphate and offcuts of roofing zinc…. 

Eve’s footprints

This series of prints is inspired by traces of ancient footprints fossilised in the earth; particularly ‘Eve’s footprint’ in South Africa, made by a woman over 100,000 years ago, and also the mile long journey by an adult and child 20,000 years ago in what is now New Mexico.

From footprint to etching

I made inky footprints from my own feet and also persuaded others with different sized feet to help out. In order to appreciate the amazing lines and contours of the skin on the soles of our feet I enlarged the original footprints many times (photoshop) – producing fascinating map like patterns.

So far so good, but my next challenge was getting these intricate images onto a printing plate…. 

Roofing zinc vs prepared zinc plates

You can buy pre prepared zinc etching plates, these are highly polished, unlike roofing zinc which is grey. I had a go at polishing it with carborundum paper and wire wool (pic) and it did come up quite shiny, but this didn’t seem to make any difference to how the finished plate printed.

The metal has a milling direction and as a result the roofing zinc plates tended to curve a bit. This means you can only do a relief roll in one direction – not ideal but manageable. If anyone has suggestions for properly flattening the plates please let me know!

Zinc is eco-friendly as it can be recycled easily many times without deteriorating. 

If you want to go down the roofing zinc route, I suggest you make friends with your local roofers to cadge their offcuts for printmaking instead of recycling.

Copper sulphate – what is it and where to get it

If you are a gardener you may have come across copper sulphate as ‘Bordeaux mixture’ and sprayed it on your peach trees to prevent peach leaf curl. Copper sulphate etching is sometimes called Bordeaux etch, and there is some more detailed information on Cedric Green’s site here. 

For etching zinc plates we use pure copper sulphate crystals, not Bordeaux mixture as it will have other chemicals added. I got mine from Hawthorn Printmakers but most printmaking suppliers supply them.

First prepare your roofing zinc plates 

Cut out your plate shape with tin snips. These can leave the edges a bit sharp so use a metal file to smooth them off, and gently round the corners so they don’t cut through your printing paper, (or hurt you). 

Seal the back of the plate with parcel tape – you don’t need to etch the back of the plate, and if you forget to seal it (yes, I did) your etching bath will be used up more quickly.  

Degrease the surface using abrasive cleaning fluid like Cif, or some whiting and vinegar with wire wool – this fizzes up dramatically. 

Handprinted have a good demo of degreasing etching plates on their blog. Once your plate is degreased make sure not to touch the surface with your fingers – it is good to get into the habit of holding it by the edges.

Creating a design on the plate; laser toner transfer 

There are lots of different resists you can use to create an image on the plate before etching it. As I wanted to use the enlarged footprint image, I decided to try laser toner transfer with acetone.

I taped the laser print face down to the plate, then wiped the back liberally with acetone which softens the toner. 

To transfer the toner to the plate you need to rub the back of the photocopy with something hard and smooth, I found the handle of an afro comb worked well. My print was the whole area of an A4 paper, so it took a while and a fair bit of elbow grease. It was worth it though – the image transferred very clearly and the toner provided a strong resist to the etching solution.

Mixing the etch; 

Nb. Avoid getting this on your skin or breathing in any dust. Wear protective gear; gloves, apron and goggles etc.

The general advice is to use 50% copper sulphate and 50% cooking salt. The salt speeds up the etching process, so use less if you want a gentler etch, which will take a bit longer. The separate ingredients here are all inert – they only start working when mixed together.

Recipe
100g copper sulphate crystals
100g table salt
1 ltr water

This amount will be good for a small A4 size tray.

Make sure the copper and salt are all completely dissolved; use 500ml hot water and stir well. Add the rest of the cold water.

Protect all your surfaces from the etch, especially any metal ones, as well as your skin. Have a bucket of water handy for rinsing things off.

Etching the plate 

Set a timer – I found 10 minutes was right, but as the etching bath becomes used it may take longer. It is a good idea to do some tests before committing a whole plate to the bath.

Carefully lay your prepared plate in the tray so the etch covers it.

Lift the plate out to check the depth of the etch, and make sure your resists aren’t being eaten away by the copper sulphate. The longer you leave it the deeper the etch will be.

Once you are happy with the depth of the etch lift your plate out, let it drip and then rinse it in the bucket. Dry it well. The zinc will probably go a bit black from oxidisation, don’t worry, this will all come off when you print it.

When you finish etching

You can re-use the bath for a long time, refreshing it by adding more dissolved copper sulphate crystals and it will last for many months.

The turquoise colour of the etching bath fades to clear with use until it no longer works – to make sure it is fully exhausted leave some metal scraps in it overnight. You can also add washing soda to fully neutralise it – test the ph with litmus strips, aiming for 7 – 8.

Printing the plate 

I printed the plate in both relief and intaglio, as well as on thick printing paper and thin tissue to use for chine colle. I was thrilled with the results and feel that it is the beginning of a lot more copper sulphate etching projects.

Thanks everyone!

Many people have been involved with this experiment; so many thanks to the friends who lent me their feet for printing, and also those who helped with advice and organised practice etching sessions, not to mention the roofers whose zinc off-cuts led to the conception of the project.

My exploration of footprints led to the realisation that the soles of everyone’s feet have their own unique map-like marks, with contour lines, hills and valleys. The prints celebrate this deep connection between the soles of our feet and the earth we walk on.

Landmarks Exhibition

See the prints which are part of Inkers Printmakers Landmarks Exhibition at West Yorkshire Print Workshop Gallery on the Piazza at 42-44 Princess Alexandra Walk,  Huddersfield, HD1 2RS 4th Oct – 15th Nov 2025