Nibs, flossing, and shims

Once upon a time, not so very many years ago, nib flossing was virtually unheard of. Yet nowadays flossing is one of the first things recommended in pen forums when solutions to ink flow problems are sought. Perhaps this is a function of the recent popularity of highly saturated boutique inks, and novelty inks with paint-like particulates ("shimmer" inks, for example). Indeed, with traditional inks, even a badly clogged pen's nib slit is easily cleaned with an ordinary detergent solution, with no need to force thin sheets of plastic or even metal between the tines.

For flossing is not risk-free. Plastic can leave residue behind, and metal can scratch the inner faces of the slit, affecting proper capillary ink flow. This is not so much an issue with brass shim stock used on stainless steel nibs, but on gold it is very much a concern. There is also the risk to the integrity of the nib's tipping, most pronounced with gold nibs with very fine tips. For nibs like the one below, sheet stock used for flossing should be introduced into the slit from the back end, not the tip, and removed in the same way.

Sideways pressure can easily detach the tipping on vintage nibs such as this Parker Vacumatic

Where things have really gotten out of hand, however, is in the use of shim stock to widen the slit. It's no accident that experienced pen professionals avoid this method, favoring careful bending of the tines instead. In addition to the risk of tipping loss and scarring of the inner faces of the slit, using a shim to force the tines directly apart in a horizontal plane puts enormous stress on the metal surrounding the vent hole. This may not be such an issue with a modern nib, made either of tough stainless steel or of thick gold that is soft and without any springiness. But with a vintage gold nib, tempered and resilient, it is all too easy to start a crack from the vent hole which will only grow as the nib is subjected to further use.

Vintage nibs with stress cracks from the vent hole