Moleskine Friendly Fountain Pens
The Fisher Space Pen is a great thing for outer space travel, underwater writing, or to write a quick IN note-card under a mudslide, but for most purposes the fountain pen holds pretty well. When using a fountain pen, there are two things to consider: the pen itself, and the ink you use to fill it.
 Moleskine Friendly Fountain Pens
For the most part, nearly any fountain pen will work in a Moleskine, provided that you fill the pen with a good ink for writing on Moleskines. Given that Moleskine paper is thinner than most fountain pen applications, you will probably have better luck with pens that are drier writers - that is, a pen that does not put down thick wet lines of ink on the page.
NOTE: Modo and Modo claims that the Moleskine Sketchbook is Fountain Pen-friendly, but in practice, many people have reported trouble with ink sitting on top of the paper, leaving the user with a wet, streaky mess.
With this in mind, here are a few pens that users have found to work well with Moleskine notebooks:
"Lamy Al-Star" : Though these are very inexpensive fountain pens (they run in the $25-$40 range) they work surprisingly well on Moleskine paper. Actually, I've found them to work better than expensive Sailor or Pelikan fountain pens loaded with a high quality ink such as Noodler's. Is this a case of a cheap pen for cheap paper? The medium nib of the Al-Star is absolutely perfect in a Moleskine. The ink goes on smoothly, it does not run or bleed through, and you can use the obverse side of the page without seeing the shadow of your previous scribblings. I use the Lamy ink cartridges and have been very pleased with the result. To be fair, the Lamy nibs do not have the silky smoothness of the Sailor pens (in my opinion the very best nibs being made today), but you will not shell out $250 or more or, far worse, be crestfallen if the pen goes missing. The Lamy is a rugged fountain pen that is perfect for travel writing or even wilderness trips.
Pelikan M805: With a Fine nib and Aurora Black ink, it flows evenly and writes with a dark line, but it doesn't bleed through the thin Moleskine pages. Though on the heavy side, you can write for long sessions with this pen without getting cramped hands. This is one of the modern classic fountain pens (if someone is steering you towards a Montblanc, check this one out first; you might save yourself enough dough for 20 Moleskine journals, without sacrificing a inch of quality). http://www.thewritingdesk.co.uk/pelikan/m805.jpg
Pelikan 800 and 400: I've had great results with fine and extra-fine nibs and Pelikan ink. No bleeding through, and the ink dries very quickly.
Omas Paragon: A light pen, made of cotton resin (for environmentally friendly writers), its Fine nib is very suitable for Moleskine journals, particularly paired with Aurora Black or Parker Quink. This is one of the few pens that blends with your hand as you write (true Italian art and technology).
Parker 51: Not in current production (allegedly the last one came out of the factory in 1962, way before our footprints reached the Moon's surface); nevertheless, it is considered a classic of classics, and with reason. The hooded nib allows this pen to be utterly reliable and dependable (though it will not write underwater). Not pocket jewelry, a writing instrument for practicing writers. (Note from another contributor: Parker is still making 51s. The updated models use cartridges or a converter. They are quite expensive, but -- as the first contributor said -- utterly reliable. (Another note (from pigpogm) - they are not still making 51s, they just brought out a pen called the "51 Special Edition" in 2002. It's not the same at all - similar look, but very different inside - doesn't have the 'collector' that made the old 51 so good. 51s are usually fairly wet writers, so may cause some feathering in Moleskines.))
Rotring 600: The Rotring 600 (especially the older style with the knurled grip) is a true workhorse pen. Get one with a F or XF nib and a converter and it writes properly the first time, every time. You can run it over without hurting it... and in a desperate scenario it could probably be used as a deadly weapon. More modern production versions of the 600 are actually called the Rotring Newton, but most fans still call them all 600s. see picture
Hero 329: Hero pens are produced in China, in a bewildering variety of models, finishes, and nibs. The 329 emulates the Parker 51 nib, although Chinese nibs run finer than the corresponding nib sizes in the West. The Hero fine nib is closer to what you may think of as an extra fine nib. Also, Heros use an aerometric type filler (in other words, a bladder that you squeeze). The Hero 329 is an excellent choice for use with the Moleskines, and at $15 is hard to beat. see picture http://www.cutepens.com/Hero/hero329/hero329blackenl1a.JPG
Hero 330: Hero 330 is similar to the Hero 329 and it too works well on Moleskine paper.
Hero 58: This is an emulation of the Parker 75 nib. I find that this pen feels "stiffer" than the 329, and the line is slightly wider. The 58's are slightly more expensive (still under $30) and come in metal, textured, and lacquer finishes that are more elegant than the plastic 329 line. see picture
Lamy Safari: For an intro-level fountain pen that writes like a much more expensive pen, the Safari is a great choice. Not extremely professional looking (comes in primary-color plastic, although there are also silver and gunmetal ones) but very reliable and durable. I've been throwing mine in a bookbag for 3 years, sometimes ignoring it for months, and it always writes perfectly the first time. see picture
Waterman Phileas: Another intro-level fountain pen that I (and at least one collegue of mine) have been writing with for almost a year now. I use the medium nib with bottled Florida Blue ink. The "float" of the ink over the Mokeskine's paper is perhaps what continues to draw me to using this pen/paper combination. At $30-$40, I must agree with a collegue that says the Phileas is "highly underated" as a writing instrument.
Sheaffer Imperial 440: I have had great luck writing in a Moleskine with a Sheaffer Imperial 440 pen, picked up for a song on eBay. Once filled with Noodler's Ink, the Imperial glides smoothly over the paper, plus it just looks cool in my pocket.
Pilot Birdie: Available as a fountain pen, with an 8mm diameter - fits neatly with a pocket moleskine. They tend to be fairly dry writers, so less feathering.
 Moleskine Friendly Fountain Pen Inks
Along with the pen, inks can make all the difference. Most fountain pen inks do not take well to thinner (or "cheaper") paper, as many of them were designed for stonger papers of an earlier era, or designed with other goals in mind (such as making sure the ink doesn't stain the pen for those that use fountain pens as jewelry, etc.)
NOTE: No matter what combination of ink and pen you use, cutting a piece of "blotting paper" to keep in your Moleskine on freshly written pages will keep any undried ink from leaving marks on other pages.
 Noodler's Fountain Pen Inks
Noodler's Ink is specially formulated with two design goals in mind: to allow fountain pens to write on today's thinner papers, and to be a nearly fraud-proof (water, bleach, carpet cleaner, etc.) way of writing documents with a pen. What this means for the casual journaler or jotter: dumping a cup of coffee on your Moleskine won't mean that you lose three months of writing.
Here are a few Noodler's Inks that users have been testing in their Moleskines:
Noodler's Bulletproof Black - A dark black ink and one of Noodler's most popular. I've used bulletproof black in both the Moleskine notebooks and Cahier, and it's worked without a hitch. A thick black line, everytime.
Noodler's Legal Lapis - A "classic" blue ink that looks quite striking on the Moleskine ivory colored paper. This ink has worked well for me in the Moleskine notebook, but it has displayed a bit of feathering in the Cahier where the Bulletproof Black did not.
 J. Herbin Inks
I've been using J. Herbin fountain pen inks with good results. I'm particularly fond of the Vert RÃ©sÃ©da (a light bluish green) but the Lierre Sauvage (a strong dark green) and Vert Olive (an olive green ink) also work well.
Unlike the Noodler's inks, the J. Herbin inks are not water proof and would, I assume, be damaged by exposure to liquids. If that's not a problem for you, they come in a wide range of colors (26!) and in bottles and cartridges.
They also have scented inks, which could make for special letters or notes.
 Fountain Pen Sources
Stipula - Pen Emporium: It was from the mastery and skills of a group of Florentine craftsmen that the history of Stipula began â€“ a history that still owes its characteristics soundness and prestige to the past. Since 1973, engulfed by the beautiful Florence scenery, we produce with passion fountain pens, rollerball pens and writing instruments for collectors, pens to use and to show off, pens for writing, for working, for dreaming..
Pentrace: Fountain pens are the main focus of this board as GTD is the main focus in 43 Folders; but some of its members have recently discovered Moleskine journals, and they are using them with FPs. In addition, a number of their members have been using notebooks for years (well, they have to use their FPs anyways).
The Fountain Pen Network: Discussions of all fountain pens, vintage and modern. Specific forums for several manufacturers, and a forum for ink.
eScribe: Email discussions archive mostly focused on pen collecting, but discussions go broad and deep into anything pen related, including Molesine journals; and, believe it or not, they have mentioned FSP several times (perhaps some former astronauts turned FPs collectors).
Richard Binder: If your FP doesn't behave the way you want (other than wanting it to write underwater, for that we have FSP), or if you want to instill some flair into your handwriting, this is the site to go. RB can customize a nib to your heart' s content. I doubt he uses Moleskines, though. Also contains huge amounts of reference material, teaching you all about the insides of many of the most popular vintage fountain pens - if you want to know what makes a Parker 51 or a Sheaffer Snorkel so special, Richard's site will show you with clear diagrams and photos.
Nibs.com: If you use FPs, you probably know John Mottishaw, another nibmeister capable of turning any nib into a smooth, breathtaking experience. Utterly friendly, his site is in itself an amazing experience. I can assure that he, at least, has seen Moleskine journals.
Nakaya: Don't be confused by the name. No fancy electronics here. Nakaya is one of the few companies in the world (perhaps the only one) that produces hand made FPs. They aren't cheap, and I doubt their pens would survive outer space travel, but they make one of the most beautiful writing instruments in this part of the galaxy. Please, don't attempt to consult with them about Moleskines.
His Nibs: Not to be confused with Nibs.com, this is a great source for Hero pens and other Asian brands. Norman Haase (His Nibs to you) will also special order hard-to-get pens and often provides significant discounts on prices.
Pens by Ryan: A wonderful site for handmade and bespoke FPs, as well as RBs and BPs. Great selection and amazing beauty. The FPs are smooth and great to work with. The FPs come with a fine nib, though extra fine, medium, nroad, and caligraphers nibs are also available. You have to check this site out for some extremely unique pens.
cutepens.com: This is a great website if you want fountain pens from Asia. This website charges no shipping and you can buy a Hero 329 for less than $10.
ISellPens.com: They carry a wide variety of Hero pens as well as a lot of other brands of both expensive and not-so-expensive fountain pens.
The Vintage Pens Website: David Nishimura sells a wide variety of extremely high-quality vintage pens (fountain and rollerball) and pencils. A good place to look for a fairly-priced high-quality Parker 51.