Glass dip pens? You got it, these things are made entirely out of glass. Handmade in France, each one is unique and a piece of art. They were all the rage in the mid-17th century, back when Herbin first started making fountain pen ink (circa 1670). Sure, they're not the most practical pens in the world, but they are novel, beautiful, and have a very functional purpose for the fountain pen enthusiast.
The Herbin Glass Pen has a spiral, fluted nib that holds onto the ink in its grooves when you dip it into your ink of choice. A small tap or roll along the mouth of the ink bottle to rid the tip of excess ink, and you're set to write! It writes thicker than a fountain pen and takes a little bit of practice to get a consistent line. it is not going to be as smooth as a fountain pen nib, and can have some variation as the tip isn't equally ground all the way around. It tends to write very wetly, so it makes inks appear to be much more saturated than they are in a fountain pen.
Aside from the aesthetics, the most significant advantage of these pens is that you can dip and test less often used inks you have lying around (or new inks you've just acquired) without going through the whole routine of flushing and filling a fountain pen. If you're trying to get a certain look, such as a vintage early-American writing look, you can grab your paper of choice and test many different inks on it quickly with the glass pen before inking up your pen of choice. You just need to be aware that since the dip pen writes heavy to start, you need to pay closer attention to the way it writes for the last few words before the pen needs to be re-dipped… that will give you the most accurate depiction of what the color will be in a fountain pen.
Check out all the Herbin Glass Dip pens here, and all other supplies at Gouletpens.com