Sodium Chloride solution 2.2V 5A, 2 hours, Mild Steel. 106mm x 55mm
John and I used a bigger tank for our electro etching. We also had a fish tank pump making bubbles of air come up from the bottom. ( We made some holes in a plastic pipe and  blocked the end )

We also tried writing on a stainless steel spoon with a CD marker and doing it for 20mins.