As part of his project to reproduce the James Watt micrometer, Machine Thinking needed to make a couple of graduated brass dials and spent a lot of time experimenting with the best way to etch the brass.
Wanting a deep etch, CerMark was out of the question, as it only leaves a slight surface mark. CNC milling was also ruled out, as he wanted to maintain sharp inside corners. This led to acid etching, usually used for circuit boards. After trying popular methods such as toner transfer, photosensitive film, and ablating layers of lacquer/paint with a laser cutter; but was unhappy with the number of steps, amount of clean up, and quality of the etch. This led Machine Thinking to use LaserTape, which is usually used in the sandblasting process. He simply applied the tape to the brass, and laser cut the design into the tape. Then he could simply peel off the parts that need to be exposed to the etchant. After rinsing he then spray painted the etch black for added depth, and once set was able to peel off the rest of the tape, leaving minimal cleanup. Check out the video below for the full details:
If you want to try this method yourself, I have found LaserTape at both Johnson Plastics and Ikonics Imaging in the US. I struggled to find the exact product from a UK supplier, but found one similar at Harbro Supplies. Always make sure that materials you put into your laser cutter do not contain PVC, as the fumes produced can damage your machine and are bad for your health.
Originally found at r/DIY