Yes, the caution about pulling the socket off the board was mainly due to an experience I had with a board a student who'd made his board in his kitchen using a high-density ink to mask the photoresist and etchant from the same kit and onto which he'd soldered through-hole sockets only one side, just as I'd suggested. I've done this myself, though not since the '70's, as I always found wire-wrap to be more practical and more durable. However, if one is careful when extracting IC's, particularly with properly installed sockets, installed as they were intended, and with proper tools, there's little risk of damaging the board or sockets. With DIP-40 sockets and extracting parts using a screwdriver, it's pretty easy to mess things up, particularly on a crudely homemade board.

The three-layer sandwiches I used back about twenty years ago were made with a small pen plotter on single-sided photosensitive and quite thin copper-clad stock using black latex ink. That stock is available in both positive and negative resist, so one can draw the layout directly on the copper, toss it in the brew, and then wash off the ink when it's etched. This doesn't work for fine-pitch parts beyond approximately .050" pitch or fine-line layouts, BTW. It also doesn't work with 0.25mm pens, as the ink won't pass a point finer than 0.35mm.

RE