The magic #s appear to be 800 zooms x 95 pews @ 225 LPI. Note that this was a pure black and white design; so, I used “vary power” and all the engraved areas are, in theory, at 95 pews with no variation.
This is without detergent or any other masking.
Wow–that didn’t affect the function of the trackpad? So cool.
Hmm… I have on of these old trackpads that I don’t use anymore (because I switched to the newer white one). I may have to experiment. 
To be totally clear, I have no idea if the trackpad still works.
I should test that.
Works fine.
Bit weird to the touch. OK, very weird to the touch. But it does work.
I would not recommend for daily use.
It looks cool but I reckon that, given the additional friction, it’ll collect grime like crazy 
It is really not at all comfortable to use.
But, hey! I had a bunch of old trackpads lying around and they make a neat discussion piece.
I wonder if it would still work with a piece of PET or TPU over it (assuming it works after being blasted with a laser anyways)?
A layer of varathane would probably work fine.
Trackpads and phones work fine through a zip lock bag, so something as thin as a coat of paint shouldn’t make a difference.
Note that the trackpad is really fragile after this.
It will crack with any kind of shock.
