This Mabie Todd Leverless was made in England in the 1930s. All the external metal is 14k gold, which one would expect to be largely immune to issues from aging. But take a look at the section overlay -- definitely also solid gold and fully hallmarked. Click on the images below for a closer view.
The surface has the appearance of a loose net, or of a greatly magnified hand-hammered finish. The net consists of incipient fracture lines with slightly flattened areas in between -- something like what you might get if you wrapped an irregularly shaped geodesic dome around a tapered cylinder. How did this happen? And why is only the section affected?
This is a result of stress corrosion cracking, discussed in
previous posts in relation to gold nibs. The way in which the section overlay was manufactured left the metal in a highly stressed state. Subsequent exposure to chemicals found in inks and especially cleaning and polishing products would have provided the other necessary ingredient to start the cracking. This would not have happened overnight: it would have been a cumulative process over a period of decades, each exposure adding imperceptibly but inevitably to the outcome visible today.
What could Mabie Todd have done differently? That's a tough question. The overlay was made by attaching a section of gold tubing to the hard rubber section with a rosin-based mastic, the only contact points being at the ends of the tube, then spinning the metal down until it was in full contact with the section throughout. Since the section was locked into the overlay the assembly could not be heated enough to relieve the internal stresses in the gold. A different alloy might have been a solution -- going to 18K would have done the trick. On the other hand, I'm not sure how common a problem this is. Perhaps this particular pen had the bad luck to be cleaned with something particularly strong. We know that ammonia solutions are bad for 14K gold, but anything containing bleach is much worse.
