If you’ve read my earlier comments on the subject you will be aware that I am not in favour of re-blacking. This is for practical and ethical reasons. Until quite recently there was no effective method of re-blacking that could be employed successfully on hard rubber pens with chasing. Potion No9 never really looked like the original black and was easily accidentally removed. If removed intentionally from a chased pen it always left many traces. Using abrasives worked to some degree but not on chased pens unless one was prepared to remove the pattern altogether. In recent times Mark Hoover’s mixture works quite well. It is messy and expensive and if you live anywhere but the U.S., importation will make it very much more expensive.
Ethically re-blacking any pen is reprehensible. You may say that you re-black only your own pens for your own pleasure in them and you will never sell them. I’m sorry to have to remind you (I hope it’s not news to you) that you won’t live forever, and then your heirs, probably not well versed in fountain pen lore, will sell them, unaware that they have been re-blacked.
Who buys a re-blacked pen? If they are sold without any declaration of what has been done to them, as they seem usually to be, the expert collector will spot them at several hundred yards, and it is the poor novice who is saddled with a faked-up pen. How will the expert know? Because he knows his pens. 1920s Watermans, for instance, like to change colour. One that has been cossetted and housed in cotton wool might survive coal-black. It will also have little in the way of evidence of handling and use, those micro-scratches and even scratches and dents that accumulate on a well used pen. It will almost certainly have lost some of its blackness. If you see a Waterman of that period, scratched up in the usual way but black as night, you’re entitled to be cautious and fear that it may be a pig’s ear posing as a silk purse and pass by on the other side.
It is true that there are some 1920s hard rubber pens that do not fade. They are not Waterman, Swan or Parker pens. If these pens are exposed to the normal measures of humidity and sunlight they will, to varying degrees, fade.
Some people like re-blacked pens, so where do the ethics come in? I cannot guess at the proportion of buyers who like re-blacked pens and I know there are many, like me, who would prefer not to have them. This affects sale prices. Is a re-blacked pen worth as much as one that retains its original colour? Probably not. Is the market perverted by the presence of undeclared re-blacked pens? Assuredly!
I understand from having had these arguments on the pen boards several times that not everyone shares my opinion and they believe that those ethics do not apply. They are just as entitled to their opinions as I am to mine, but their opinions are, of course, wrong!