The edinburgh etch was invented by Friedhard Kiekeben and here is a bigger description of the process
Basically it consists of 4 parts ferric chloride solution and 1 part citric acid solution.
Using just ferric chloride, the etch is very slow and the residue has to be frequently brushed away for the etch to continue.
The addition of citric acid speeds up the bite of ferric chloride, and also removes the sediment that was left behind previously.
So you get a quick working solution with out having to call in the Hazmat team.
For myself, I just needed a quick process to etch a simple design on a brass foot plate for my latest fantasy creation I am building.
The brass foot plate.
First I trace out the outline and then with a HB pencil, I draw the outline of the shape I want.
I only draw one side.
I want to make a mirror image, so I fold the paper in half once the one side is finished.
With the paper folded in half, I scribble on it using the back of the plastic marker shown.
This causes the pencil lead to transfer to the other side.
Then I darken the image and clean it up on the left and then I use a copy machine to make a copy of the image.
I do this just so that if things go wrong I have the original still.
Then I take the footplate and stick packing tape on both sides, making sure that the edges are also well covered.
Then I use a clear glue to glue the paper to the tape on the foot plate.
Once the glue is dry I use a scalpel blade to cut through the paper and the tape at the same time.
Then I peel the cut part off.
Once the design is exposed, I pull the remains of the paper off as well.
I mix up a small amount of ferric chloride and citric acid.
This is a one off job so I throw the spent mordant away.
I wasn't in a hurry so I left it in the solution for about 5 hours and that removed about a third of a millimeter from the surface.
Then I used a liver of sulfur to blacken and high light the recessed areas .
I wanted the black not to be too dark.
Inside the cabin.
The edinburgh etch can also be used for finer applications.
Here is a picture of a very beautiful woman.
The picture is then prepare in photo shop.
I made an action in photo shop for this sequence, so it is easy to do this for all photo's.
The image is reversed and printed with a laser printer onto a sheet of PnP.
Then I used an iron to heat the laser printing up and transfer the image to the brass.
Then it is etched in the same manner as I described.
I thought it came out quite nice.