adhesive backed vinyl or other resist for your pattern
mild steel plate: .125" cold rolled steelASTM-A366/1008
Copper Sulfate Crystals
Fish tank air bubbler
wood or plastic stir sticks
plastic tweezers (optional)
Although copper sulfate is a comparatively safe chemical for etching, it is considered a marine pollutant, and if present in rivers or lakes it can kill fish. It is crucial that solutions containing this salt are never poured down a drain without following the above instructions. Only a spent solution that is lacking the green coloration (which indicates the presence of copper ions) and that has been neutralized with sodium carbonate is safe to be discarded.
Create your pattern. You will need a template or pattern that you want to etch. For the alligator texture I used a pattern I found on the Silhouette design website and used my Silhouette Curio to cut out the pattern in adhesive backed vinyl. You can cut out your own pattern, or use a stencil and oil based paint (even nail polish will work!).
Clean your steel plate to make sure its oil free and has a smooth surface. Then place your design on the plate and burnish (rub it with a wooden dowel, your fingers or whatever you have handy) it so it is firmly stuck on. Then you want to cover any other areas of the plate you dont want to etch with packing tape or left over vinyl.
Create the etching solution. Put on your safety glasses and rubber gloves, then in a glass container big enough to hold 4 cups of liquid, mix 1/2 cup of table salt and 1/2cup of Copper Sulfate crystals. Stir the crystals together using a wooden stir stick. Add 4 cups of hot water and gently stir with a wood or plastic utensil until the crystals are dissolved. I used boiling tap water and slowly add to the crystals. It makes a beautiful teal colour!
Add agitation to the water with the fish tank air pump and hose. I bought a new one from the local pet store, but you can find them used at your local Value Village/reuse store. Tape the air hose to the side of your container so it stays put. Put your steel plate into the solution, pattern side facing down and plug in the air pump. Set your timer for 30 minutes and go have a snack.
After 30 minutes, turn off the air pump and gently lift out the texture plate. Its going to have a bunch of copper coloured stuff on it, this is normal! Take the soft toothbrush and gently brush off the crud onto a paper towel and dispose of it in the garbage. Put the plate back into the solution and turn the air pump back on. Set your timer for 30 minutes and go catch up on your shows.
Turn off the air pump and pull out your plate. Brush off the copper residue into the garbage and rinse off the plate under running water. Remove the template/resist and give the plate a good scrub. Once a plate has been etched to the required depth and rinsed it is crucial to blot off any remaining dampness with paper towels and then speed dry plates otherwise the steel surface will quickly rust.
Your new texture plate is ready to use! You can use it in your rolling mill or with a press or hammer.
You can use your etching solution several times, as long as the solution is still green it should still be active. You can also add some new salt and copper sulfate crystals to refresh the solution.
The Copper Sulfate Etch works so wonderfully as an etching bath - by the depletion of copper ions. Concentrated copper ions are regarded as an aquatic pollutant and must not be allowed to get into waste water. As more and more copper ions react with the metal plate during etching these are converted into their inert cousins: solid copper atoms (the gunk you brushed off). If a sufficient quantity of metal is etched, eventually all copper ions are removed. A fully depleted bath is recognizable by two features: (a) the solution no longer corrodes metal and (b) the solution is no longer green, it is clear. Spent solution easily separates into a clear liquid and solid particles.
How To Prepare a spent etching bath for recycling:
1 Add hot water to the bath to re-dissolve any solid sulfate particles and stir. 2 Add a pile of metal off-cuts - zinc, steel or aluminum - to the tray 3 Leave to act overnight. 4 On the following day, drain off the liquid into a bucket and add sodium carbonate (about two or three cups per bucket). 5 Once fizzing stops the liquid can be discarded. 6 The remaining solids can now be left to dry out. Keep in labeled, sealed containers and then treat as dry waste.