The Writing Desk Reference Section: Questions about ink
Is it safe to use Noodler's or Private Reserve ink in a vintage pen?
This has been a hotly debated subject on many internet fora. Highly saturated inks, such as Private Reserve, have been reported to cause staining to some plastics used in vintage pens. Some pen repairers even refuse to guarantee their work of such inks are used.
Our advice is to not use Private Reserve (or other highly saturated inks such as Noodler's) in a pen made from casein (eg early Conway Stewart and Burnham pens). Also, we advise caution with pens made from celluloid (most vintage pens with marbled or translucent parts) just in case. The ink won't harm your pen but there is a chance that permanent staining could occur if the ink comes into contact with the coloured parts of the pen (black front sections etc are usually made from hard rubber, also known as ebonite, that will not be affected).
Modern (non-metallic) pens are usually made from acrylic resin (known also as PMMA, Perspex, Lucite, Plexiglass etc). This material is very stable and largely stain resistant, although sometimes discolouration can be experienced in demonstrator models. Some vintage pens are made from acrylic resin, for example the Parker 51 and Sheaffer Snorkel.