Making safety pens yet safer

A customer was recently asking about safety pen leakage. A safety with good seals should be as leakproof as any fountain pen could be. That doesn't mean, however, that it can't leave a mess quite without any leakage. One example is how ink can end up spattering in tiny droplets when the nib is extended if there happens to be a film of ink spanning the barrel opening when the pen is uncapped, like the soap solution across a bubble-blowing wand.

My customer's issue was something a bit different, though. It seems it was a matter of ink sticking to the plug inside the cap. When the cap is tightened the plug is pressed firmly against the barrel mouth, as can be seen in the photos above and below. Yet as the closeup below shows, any ink that ends up sticking to the face of the plug is going to drip into the threads once the cap is removed and set on its side. And from the cap threads it will soon enough end up on the barrel threads and thence on the writer's fingers.

I've never seen any discussion of how to deal with this issue -- neither in original instructions and repair manuals, nor by modern-day collectors or repairmen. So here is a solution I came up with: 

Moisten a cotton swab with a little alcohol and clean off the face of the plug, then once it is dry use another swab to give it a thin coat of wax. This should greatly reduce the ability of ink to stick to the plug, and is similar to how ink bottle caps are typically equipped with a sealing disk of ink-shedding plastic.

For anyone contemplating making new safety pens, I would suggest making the plug out of a modern material that is inherently ink-shedding. Teflon immediately comes to mind, though acetals such as Delrin are also quite hydrophobic and much easier to machine.