A fountain pen was accidentally filled with china ink. When it dried out, it was completely clogged. Water alone doesn't help and ultrasonic cleaner bath doesn't seem to change anything.
Is there some mild chemical which can be soaked into the pen and solve the ink to ease the cleaning with the ultrasonic cleaner bath?
Or what other means do I have besides paying an expensive repair service?
China [aka india] ink contains carbon and varnish [or perhaps shellac] to produce a distinctive long-lasting black coat which when dry is waterproof.
No amount of water will dissolve the hardened ink residue.
Shellac is easier to remove than varnish so test the pen first with denatured alcohol. If the ink liquefies, it contains shellac; if it gets soft but doesn't dissolve, it contains a mixture of shellac and lacquer. Test the pen again with lacquer thinner; if it liquefies, it's lacquer. Shellac can be removed with denatured alcohol, lacquer with lacquer thinner, and a shellac-lacquer combination with a 50-50 mixture of denatured alcohol and lacquer thinner.
If the ink contained varnish (which is most likely), you will need something to dissolve the varnish such as varnish remover. Let the parts soak in a solution in a glass jar. If you have access to an ultrasonic vibrator, put the whole jar into the water bath to increase varnish remover efficiency. Check it after several minutes to see how it's going. If the liquid in the jar starts to turn black, it's working.
Good luck.
Get some technical pen cleaner from your local hobby shop... Rapidoeze, I found some guy recommends this, he used it on old fountain pens from the 70's.
It is quite likely only the nib which has become clogged.
Just buy a new nib. It is quite easy to remove and refit - although you'll get inky fingers!
Some of them pull out and some unscrew.
Here is a video showing how to change one type.
I had a similar issue with India ink (which I believe is a term used interchangeably with China ink). I tried a DIY fountain pen cleaner, which worked OK but not completely. It wasn't a very expensive or sensitive pen so I ended up moving to Koh-I-Noor Rapido-Eze Pen Cleaning Concentrate which worked much better. I've also had good luck with Rotring's Cleaning Fluid for technical pens, which is a very similar (if not the same) formulation. That stuff will cut right through these inks in a way that a fountain pen cleaning solution will not.
