I decided to try and experiment with colouring copper using fire. Let’s try and see what works!
First, a few words on safety. In this project, I use a strong etchant and fire. I only worked outside in a clear area with proper PPE to protect my skin and eyes. Long sleeves, long pants, gloves, safety glasses, no open-toed footwear, and no hanging items or jewlery. My long hair (at the time) was tied back. I worked with a fire extinguisher within reach when using my torch and a neutralizing chemical bath of water and baking soda within reach when working with the etching acid. I also had a water sprayer to wet-down the working area outside before using the torch, and to cool down the copper sheet afterwards.
First, I tried applying a vinyl stencil of Nf island and using the etchant on the copper. I applied several coats on the face of the copper to try and get a deep etch on the sheet. I hoped to use a fine grit sandpaper to bring out the details of the relief later. I submerge the plate in the neutralizing bath to halt the reaction, rinse the copper with water, and dry with paper towel. Afterwards, I use extra paper towel to soak up the left over chemicals and store them in a plastic container to later dispose with hazardous wastes. You cannot just dump copper ions down a drain or onto the ground.
There was a visible relief between the exposed and masked copper, not just the difference in how shiny they were. I think in future I would let the etchant sit for longer to get a deeper etch, though.
Next, I broke-out my torch to scorch the copper and see what colours I can get. I didn’t want to over work the copper with heat, so first moved the flame about to evenly heat up it up. Then I started focusing the flame at different spots, seeing how the colours change. I followed the line of relief that I had etched into the sheet to try and keep a contrast between the background and the Island.
And here’s where my plan did not work out: the buffing/fine-grit sanding did not effectively bring out the lines of relief achieved with the etching. I decided to flip the sheet over and try a different approach on the other side.
Okay, Plan B: torch the whole sheet first, then put a chemical patina on the background. I happened to have another Nf island stencil on-hand, but a smidge too tall for a landscape at this size, so I’ll make a portrait orientation instead.
I re-torch the copper sheet to get random colour patterns, then cover the sheet with the stencil. I remove the background, apply chemicals, and put in the chamber to react. I hope to get a good blue/green background, but we’ll see!
A few hours later, I see some blue forming, but a lot of darker browns. When I rinse with water, most of the blue gets washed away, but not too bad. There are many interesting patterns in the background, a bit like an aged leather, so I decide to move forward. I remove the remaining vinyl and apply clear coat.
I use a simple off-the-shelf 11×14″ picture frame with the piece because the copper sheet is too easily bent without some kind of protection, plus it warped slightly during the heating process. If I had the right blacksmithing tools, I might try to hammer the sheet flat before considering other mounting methods.
I think I’ll definitely use the torch to colour copper in the future, but now I have a better game plan. I’ll know to torch the copper sheet first, before applying a chemical patina, and that I can keep different options open, like using paint – I kind of like the way the torch marks looked with the vinyl still on the surface. I could still use etching, but save that for after torching as well, just try masking the flame marks that I want to keep.