When I built the Triaparator I got more questions about how I did the etching then how I designed and built the irises — well here is how I made them:

The general idea behind etching is that you cover the metal to be etched by the acid with something that will prevent or resist the acid from reacting with the metal. This is called the resist. There are resists you can you including wax and asphaltum. You then remove the resist from the regions you want the etch and then expose the metal to the acid. The acid reacts with the exposed regions, chemically removing the metal. Now the image that you removed from the resist is etched into the metal. My friend Kathy Nagel uses this method to make some beautiful prints by inking the etching and pressing it into paper.

However, I suck at drawing by hand and most of the images I generate start off on the computer. So carving the images into the resist is not for me. Instead I use laser print toner as the resist. First let me say that while I have modified the method and materials slightly I learned how do this from both the Steampunk Workshop and my buddy Max Chen who showed me how to do this with PCB etching supplies .

Here is what you’ll need:

A computer

A Laser Printer

Glossy Inkjet photopaper

Abrasive pads

Acetone and a clean cloth

An old iron

Plastic contaitner

Nitric Acid

Step 1: Design your image

I designed these circuit board style images in Illustrator CS3.

A few key points about this step.

• Remember the toner is the resist so if you if you draw a black line on a white background this will result in a bight line on a dark background. So I recommend generating a black background and drawing you image in white.
• You’ll see exactly why in the next step but you need to print the mirror image of what you want etched. This is most critical with etching text.

Step 2: Print your image

• You need to print you image onto glossy, inkjet photo paper using a laser printer.
• Do not get grease or dirt on this printout and do not let is get bent or dimpled

Step 3: Prep you paper and metal

• I found it very important that the toner go all the way up to the edge of the paper. I cut the image out and leave about a 0.5″ margin of toner around it.
• Clean and rough the brass. This is very important. First I use an angle grinder with a fine abrasive polish pad to remove a thin upper layer of the brass. I then rough it, by hand, with coarse abrasive padding. I go horizontal, vertical and then both cross hatches. Then I repeatedly wipe the brass down with acetone and a clean spot of cloth until the cloth stays clean. Once this done do not touch the brass on this side.
• Below you can see the rought brass and the photo paper reay to go.

Step 4: Transfer the toner

• I found a medium heat on the iron works better then a high heat. The high heat is more likely to over heat the toner and result in spotted and blurred images.
• I also found the preheating the brass was key. I place the dirty side on the iron until it is hot to the touch.
• I then quickly lay the image down and apply the iron.
• Pressure is the key to the transfer more then the heat so really lean on it. If the image is larger the your iron be sure to get all the regions evenly. Pay extra attention to the edges.

• You’ll know when the toner is fully transfered when you can star to see the image through the paper. It’s faint and this may not happen for all papers (I use Kodak ) but it was a great indicator of weather an area need more time to transfer or not
• Below you can see that the image is some what visible and that the edges are fully sucked onto the brass

Step 5: Remove the paper

• Once the toner is fully transfered I dribble some cold water directly onto it. Others will recommend that you fully submerge piece. I do not do this and do not recommend it.
• Once its wet being gently rubbing it with your finger. You’ll see the paper starts to ball up and come off very rapidly.
• Be very carful doing this. Too hard and and you will remove very fine lines of toner.

• In this photo you can see that some of the brass in the center is being exposed. This is fine. It’s also a good sing that you are almost done removing the paper.

• Here you can see that the paper is really starting to come off easily and so is the thin layer of plastic below it. The Steampunk Workshop recommends fully removing this layer and exposing all the brass. I leave it there. I’m always tempted to remove it fully but sometimes it does not come off so nicely and remove the toner setting you back to the beginning. I let the acid remove this final layer, as we’ll see in the next step.

• Once almost all the paper is off, leaving just the plastic, cut away any extra brass. I leave a little bit on the end so I can see and feel how far the etching has gone without disturbing the principle image.

Step 6: The Acid

• I then place the piece in the nitric acid bath.
• Remember that brass has allot of copper in it and copper and nitric acid do not play well with each other. the initial reaction will be exothermic and produce Nitrogen Dioxide which is very bad for you. Ventilation and respirators are highly recommend.
• In a few minuets the rest of the paper ad plastic slides right off.
• Let this sit in the acid until you have the etch you want.

• When you have the etch you want remove it form the acid and clean it with water.
• Below you can see how the exposed bras is recessed

• Then clean off the remaining toner with acetone.

Step 6: The Patina

• You can also you paint for this step. But I have found that the patina works much better.
• Once the brass is clean put it in the patina until the desired color is reached

• Here are the three etching after the are remove from the patina and allowed to dry

Final Step: Sand

• Once the patina is dry you sand back the high spots.
• Do not use your finger to sand as they will get into the etched bits are remove the patina from it.
• Use a sanding block and very fine sand paper.
• Below are the final three etching

The etchings are going on the tray.