I have just been reading the account of etching the nameplates for a loco in the latest M.E. It brought to mind a couple of tips that I was given by the staff of a firm who did this sort of thing professionally for the electronics and printing industry. I was actually getting some photo resist from them, and while there, I was told that if using ferric chloride (they no longer did), if the action seemed a bit slow, don't add more crystals. Instead, dilute it a bit more with airated water. Oxygen is a catalyst to the reaction and it should speed things up. They actually applied the etchant via a foam pad through which they bubbled air, and the bubbles burst onto the work. Another tip, was to fix the work to something which allows the work to be held in the etchant face down to allow the debris to fall away, and rock it gently at the same time. I followed their advice and made two very satisfactory plates for a Robey steam tractor that I was building, (since disposed of). I hope this may be of help to someone.

Maurice