I'm charged with cleaning up a number of modern fountain pens. Some of them are Namiki and Sailor Maki-e pens. The bodies of others are brass, silver and unknown synthetics. All appear to have gold or silver nibs.

It appears that the original owner would buy a pen, use it for a while, put it away without cleaning it, and then buy a new/different pen. Many of these pens have sat in that condition for perhaps as long as 20 years.

I've had fairly good luck repeatedly soaking the pieces in distilled water - at least those I am able to disassemble at all. A few are pretty well stuck, but at least one yielded to the water after about a week of soaking and rinsing episodes.

Those have all been pens with the metal bodies.

I would like to know if I can continue this practice with the Maki-e and synthetic body pens without risking damage.

(I realize that no one can speculate on unknown synthetics. I'm looking more for a general sense of how well modern synthetic pens stand up to such treatment.)

Can I soak the really persistently stuck pens or parts in something like Monteverde Pen Flush?

What about something stronger like mineral spirits or acetone? (I won't be putting Maki-e pens in the acetone.)

These are all really nice pens and I'd like to see them cleaned up, so any suggestions would be appreciated.

Thanks