I replaced my first Esterbrook sac yesterday thanks to the info in this post. Thank you!
My pen had been restored just a few years ago. Not sure why the sac failed. But, thankfully, getting the section out was very simple. I do have a question, however. I got some traces of shellac on the section. Can I safely use alcohol to clean it up (being careful, obviously, not to get any alcohol on the nipple/shellac/sac area)? Is regular isopropyl alcohol OK?
The section of an Esterbrook J is made from hard rubber. It is safe to get some alcohol on it but it can cause the HR to fade but will not damage it structurally as it might an acetate barrel.
If you want to remove some shellac you can use mineral spirits.