The inspiration for this post hit me when I was reviewing a vintage Arnold pen, it has a super cheap plastic feed. Once I got to researching the topic, reading the vast number of opinions and thoughts it became clear this was going to be a long post. How was I to organize it: fact vs fiction, plastic vs ebonite, pros vs cons… It quickly became obvious that I needed to split the topic into 2 posts so I can stay within the 600-word self mandate.
What is ebonite? It’s a vulcanized natural rubber used as an inexpensive replacement for ebony wood. What is ABS (acrylonitrile butadiene styrene) plastic? It’s an inexpensive replacement for ebonite. Now that we have established both are cost saving solutions to a manufacturing challenge we can move on.
The Feed
Let’s start with a quick primer on fountain pen mechanics. The feed is the part that sits under the nib and supplies ink from inside the pen. Contemporary feeds are usually made of plastic, while vintage feeds are made of ebonite. Feeds contains 1 or more ink channels to draw ink from inside the pen using capillary action (thank Leonardo da Vinci) — the nib’s ink slit draws the ink from the feed to the tip. Most feeds have distinctive fins to hold excess ink thus regulating the ink flow.
For the feed to work, it needs to be sitting flush against the underside of the nib, free of clogs in the ink channel or fins. These tiny channels allow air to flow into the ink reservoir while ink flows down. Ink flow depends upon the width of both the ink channel and air channel. The ink also needs to be of the correct viscosity for capillary action to pull it through the feed, this means NO India ink in fountain pens!
The Physics
Wetting or wettability – is the ability of ink to maintain contact with a solid surface (the feed). Adhesive forces between the ink and the feed cause the ink to spread across the surface of the feed via capillary action. Capillary action is when a liquid automatically draws itself into thin tubes. The most common example of capillary action is water spreading across a paper towel. For more in-depth discussion on fountain pen physics I recommend this article on Ravens March Fountain Pens.
Ebonite feed
Ebonite is favored because it is easily wetted with ink and it won’t bead up on an ebonite surface because it is textured. The milling process naturally leaves micro scratches on the feed which are required for capillary action. Machining ebonite is a difficult process, the tools need to be kept sharp. Each ebonite feed is made on an individual basis by hand – workmanship.
With ebonite, you can make adjustments to the feed as needed. The feed can be sanded, milled, or bent to increase or decrease ink flow. The Noodlers flex line of pens uses an ebonite feed for this very reason. Those pens often require adjustments to correct their ink flow and this is only possible with an ebonite feed.
Cons
Each Ebonite feed is hand cut and finished, making them subject to quality issues and expensive. The milling process is also a strike against ebonite as ebonite feeds cannot be created by a laser. It’s time-consuming work on a lathe and mill, using metal tools some as small as .015mm in diameter. The ebonite is very abrasive thus the tooling has a very short life, adding to the cost. The ability to repeatedly cut the same-sized groove is nearly impossible and groove size impacts ink flow.
Besides, have you ever noticed how long it takes to wash an ebonite feed?
To Be Continued ……
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