It is appropriate that the word “demonstrator” begins with “demon”. I have never liked pens of this type. Their skeletal appearance has no aesthetic charm for me. Their benefit, supposedly, is that they show how much ink remains, not something I have ever cared about as I always have several pens available. Originally the intention was that a salesman could show how the pen worked. I know how a piston filler works, having pulled loads of them apart.
I bought this one because it was a cheap piston filler. It’s a Fountain Pen Revolution Indus, which I think is a rebadged Click Tulip. These pens have proved popular, both because they are quite well made and because they offer the opportunity of using alternative nibs, something which has become popular recently.
Where the “demon” part comes in is in that the section stains readily. Because these stains offend my eye I made a determined effort to remove them. I set up a little jig in the ultrasonic cleaner to immerse the section while keeping the rest of the pen out of the fluid. Several hours later the stains had hardly moved. Ink trapped in the cap did eventually succumb to the ultrasonic but the section remained intractable.
This wouldn’t matter a bit if the pen was not transparent. Every pen I restore has a coating of ink in the section. I remove most of it with water and cotton buds but I am sure that permanent traces of ink are left behind, but who cares? Out of sight etc. It seems that with demonstrators we give ourselves problems that outweigh any notional benefits the thing might have.