I saw a nice glass pen at Straits Commercial, a local art store here in Singapore, recently and it was selling at a good price. So I bought one to try.
The prices of glass pens can range from US $5 to something quite expensive. The one that I bought on eBay was quite affordable and came with free shipping.
There are many designs you can choose from. Mine is considered quite simple.
I'm not sure how these are created but they do look good.
There are deep groves to hold the ink. The only downside is it can be difficult to clean off pigmented ink once the ink gets stuck to the surface. You might have to use dish washer or fountain pen cleaning liquid.
Anyway, after the ink has dried, it should not affect other inks you dip into.
As the groved section is quite big, you need to use an ink bottle with an opening that's large enough.
Writing and drawing with the glass dip pen feels like using a medium tip. This glass tip can only produce consistently thick lines. There's no line variation of course, as expected since glass obviously cannot flex.
Since the groves hold a good amount of ink, you can write or draw for long periods of time without the need to reload.
The only downside I can think of is glass is fragile. Once dropped, the pen is pretty much destroyed.
Overall, it's still kinda worth the money considering that it's not too expensive. It's quite a fancy feeling to draw with a glass dip pen. It actually lasts longer compared to metal tip dip pens because glass does not rust. But the limitation is you only get one thickness for the stroke.
You might be able to find this on Jackson's Art Supplies (UK) too.