Acid Etching

  One of my favourite processes we used was acid etching. I used an acid proof varnish to paint onto the tin plated steel, and waited for it to dry. Once it was dry, I painted another coat of varnish so it was thicker. When it was completely dry, I dropped my piece of metal into 30% nitric acid and waited for about three minutes.

  Once the visible metal had turned a dull grey colour, I took the metal out of the acid using tongs and put it in water. When I took it out of the water I had to dry it quickly so it wouldn't rust. I used methylated spirit to take the varnish off, which exposed the shiny metal that hadn't been exposed to the acid. There was a contrast between the shiny and the dull, but I wanted to create more difference between the background and the pattern.

   To make the background a different colour, I used a blow torch to heat the metal. As it heated up, the exposed steel changed colour, but the tin on top stayed the same. I had to be careful not to overheat the metal, or it would go too far past the colours and return to grey.

  The pattern of the tin stands out more on the coloured background, and the blowtorch creates interesting random patches because the heat is not constant over all the metal.

  On my cityscape, I held the heat on for too long, and as a result the background went past blue, to grey, so wasn't as dark as I wanted, but on my leopard print panel, I used the micro welder on a low setting, so I could control the heat better, and got the full range of colours, purple, dark blue, light blue, pink and straw coloured.



When you look very closely at the surface of the metal, the parts that have been corroded by the acid are not smooth, but have tiny dimples and a rough texture. I like this effect because it takes away all the properties people associate with metal, so it has the colour and texture of a different material.