Without ink, pens aren't very useful, and we're Cult Pens, so that would be Bad. We like pens, so we like ink. So we've written this inkredible guide to tell you all about ink. It'll be good to dip in to, and should really make you think. If you're inkterested in ink, keep reading. And if you hate puns, maybe you should never have started reading.
We're a pen shop, so we'll be concentrating mainly on ink that's used in pens, for writing and drawing. We'll cover printing ink, election ink and squid ink, but only briefly. You'll need to turn to the pages of Cephalopod Monthly if squid ink is your main interest.
What is Ink?
In general, ink is a mixture of colour (though that colour is often black) and some sort of binder/carrier. It could be as simple as soot in water, or a complex mixture of pigments, dyes and all sorts of other ingredients.
Ink as used in pens tends to be one of a few specific types. Fountain pens and liquid-ink rollerballs use ink that's mostly coloured dye in water. Small amounts of other ingredients can make a big difference to things like drying time and surface tension, which controls how it flows, but most are reasonably simple.
Ballpoints use a paste ink, which is thicker. The rough ball pulls the ink out of the refill, onto the paper. The thickness of the ink (the viscosity) makes leaking fairly unlikely, and because ballpoints are so commonly used, almost all paper is made for ballpoint ink to adhere to well.
Gel ink is a relatively recent invention, in ink terms, and it's thixotropic, which means it's fairly solid when it's at rest, but becomes more liquid when it's moved. To put it more technically, its viscosity is reduced when a shearing force is applied to it. It's the same effect that makes solid emulsion paint work, and makes too much ketchup fall out of the bottle at once when you give it a shake. And to those of you young enough to only know ketchup in squeezy bottles, you have no idea of the struggles we have lived through.
Hybrid ink is another (even more) recent development, and can cover quite a variety of inks. It's usually used to refer to inks that attempt to combine the properties of gel ink and ballpoint ink. The result can be closer to one type or the other, depending on the manufacturer, but is generally like a very smooth ballpoint, putting down a more densely-coloured line.
Calligraphy inks often look just like fountain pen inks, but can be very different. They usually use pigment instead of dye, which would be likely to clog a fountain pen's feed, and they sometimes contain some shellac to make the result shiny. Beautiful when used with a dip pen, but they shouldn't be used in fountain pens, unless you don't mind a serious risk of ruining the pen!
We'll come back to all these types later, with more information.
History of Ink
Ink has been in use by humans, in some form, for over 4,500 years. Early inks were often a mix of some form of fine carbon particles mixed with some form of glue. This would be left to set into solid forms, then a wet brush could be used to turn the convenient solid ink blocks into ink as needed.
Iron gall inks have been used for over 1,500 years, especially where permanence is needed. In the longer term, though, the acid content of these inks can be a problem, eating away at the paper they're used on.
The invention of the printing press required the invention of a different type of ink, which could stick to the letters, rather than just dripping off them. This paste ink came in useful for pens when it formed the basis of the ink used in ballpoint pens.
Many of the later developments can be viewed as a way of trying to fix a previous problem, or combine the best features of previous types of pens and inks. The ballpoint, for example, was a great answer to the problem of leaking fountain pens that needed to be refilled regularly, though we should probably add that fountain pens have come a long way since then, and are much less fussy to use these days!
The first rollerball pens were intended to bring the smoothness of writing with a fountain pen to a pen with the convenience of a ballpoint. They used an ink very similar to fountain pens, and a smooth ball in place of the rough ball in a ballpoint pen.
Gel pens had most of the nice features of those rollerballs, but the gel ink could hold densely coloured pigment, giving much stronger lines, and even opened up new possibilities of ink that contained cosmetic-grade glass or glitter so your writing could shine and sparkle!
Hybrid inks brought a bit more of the ballpoint experience back to gel pens, but retaining the smoothness and dense colour. Gel is a bit 'binary' - it's either flowing or not, so if you use varied pressure when writing, gel pens can skip when you press lightly, and 'tramline' when you press too hard. Hybrid ink behaves differently, and tends to give very fine lines with light pressure, and thicker lines with heavy pressure, bringing back some of the expressiveness that fountain pens and ballpoint pens do so nicely.
Each new type of ink and pen has been better for some people, but not for everyone. There are plenty of people who still prefer fountain pens, and plenty who still love ballpoints, but that doesn't mean gel and hybrid inks have failed. We're all different, and there are those who love each type.
Types of Ink
Inks Used in Pens
A rather important category for us, here we'll look at types of ink that are used in pen refills - the types of pens where you buy a refill, not just putting spare ink into the pen.
Technically, the first ballpoint pen was invented in 1888 by John Loud, but it wasn't very useful for writing, and didn't get very far. A lot of the reason was that it didn't use ballpoint ink. In some ways, it was more like the first rollerball pen. As is rather well known now, László Bíró gave us the first really usable ballpoint pen, and it's because of him and the company he founded with his name, that many people still refer to ballpoint pens as 'biros'.
He came at the problem from the other end. He was a newspaper editor, and was frustrated by two aspects of fountain pens - the time spent filling them, and the smudging that could happen while waiting for the ink to dry. His printing press didn't have these problems. A small amount of ink was used, and was dry almost immediately. So he decided to make a pen that would use the same sort of ink.
The press needed thick ink, in the form or a paste, as liquid ink would just drip off the letters. The ink used would stick to the lettering, in small amounts, and would dry very quickly, so it wouldn't smudge or spread as the paper was moved through the press. Ink like that wouldn't flow through a fountain pen's feed, because it was so thick, but László found a way to make a pen that could use such thick ink, with a rough ball at the tip to pull the ink out of its tube, and transfer it to the paper.
That makes it sound easy, but there were many years of research from having the idea to making actual working pens that people would want to use, but the hard work paid off for László, and his pens were a huge success.
Along with his own company, he licensed the rights to make ballpoint pens, using the same techniques, to many other companies. Marcel Bich was an engineer in France, successfully making fountain pen and mechanical pencil parts, and he wanted to expand. He paid $2 million USD in 1953 (equivalent to over $18 million today) to buy the patent for László's ballpoint pens, to make his own. That venture could be said to be something of a success too - for the branding, he shortened his surname so the pronunciation would be more obvious elsewhere in the world, becoming known as Bic. You may have heard of his company.
There are many types of liquid ink - most inks are liquids, but we're looking particularly at liquid inks as used in pens. We'll get to fountain pens later - we're looking specifically at pens with pre-built refills including new tips here.
Rollerball pens are the most common type of pen to use liquid ink. According to Pentel, the world's first rollerball was the still-iconic Ball Pentel, usually with its bright green barrel, with that little colour-coded piece in the cap, next to the clip, that anyone of the right age group will remember from school days. Often as the pens that were too good for them to use, reserved only for the teacher. OHTO say they made the first rollerball pen, though, in 1963, so we may have to let them argue it out between themselves!
A little note on terminology here - 'rollerball pen' can also include pens using gel ink, though 'gel pen' is commonly used to mean specifically those. If you want to refer just to the liquid-ink type, you end up with the rather clumsy-sounding 'Liquid-ink rollerball pens' term.
Where a ballpoint pen has a rough ball that pulls the thick paste ink onto the paper, a rollerball uses a smooth ball. When used with liquid ink, the tiny gap around the ball can allow ink through on contact with paper. It doesn't actually require the ball to turn, though it usually does rotate in use, but the tiny gap around the ball lets the ink get to the paper. The result is a much smoother feel, with ink flowing as soon as the tip touches the paper, much like a fountain pen.
Like a fountain pen, though, the rollerball is also more fussy about the paper it's used on, with the ink easily flowing into absorbent paper, and not adhering at all to shiny paper. The ballpoint still had its advantages, but for some people, the liquid-ink rollerball was the perfect combination.
Liquid ink is used in other types of pen, though not as commonly, at least here in the UK. The fude pen is a popular type of pen in Japan, where brush calligraphy is an important skill. Pens with brush-shaped tips, often made of some sort of foam or flexible plastic, make for a far more convenient and pocketable pen for brush writing on the go. While not so important for writing in the west, they're proving to be popular for modern styles of calligraphy, and many artists love the variable and expressive lines they can make.
Felt tips use liquid ink, and while they're often seen as being primarily for colouring in, for children, they can be far more versatile than that - and plenty of adults enjoy colouring as a relaxing pastime too. The pen that made Pentel such a successful company was the Pentel Sign Pen, which is a liquid-ink felt-tip pen made for writing. Sign Pen is used as a general term for any pen with a reasonably thick, usually conical, fibre-tip, that's intended for writing.
Marker pens use a different type of liquid ink, often alcohol-based, to mark all sorts of different surfaces. It's a bit of a general term, and can cover all sorts of different pens for different purposes. A permanent marker is very similar to a felt tip, mainly just using different ink. Markers also include pens filled with various types of paint, but definitions can be a bit vague there too. The wonderfully versatile Uni POSCA markers use ink that's sometimes called 'pigment ink', and sometimes 'paint'. Other paint markers use oil-based paint, which is a bit different to ink, but depending on exactly how you define the terms, could be a type of ink too!
The broad 'Marker pens' category can also include Art markers, like the hugely successful Copic range, with alcohol-based ink in hundreds of colours, and different tips that can be swapped out, totally changing what each pen can do. At their heart, though, is this huge range of inks, all blendable to make almost any possible colour, and to make smooth transitions from one colour to another.
Gel ink pens are a relatively recent invention, first made by Sakura in 1984. The ink is a suspension of pigment in a water-based gel. Much like ketchup or solid emulsion paint, the gel is fairly solid when it's at rest, but when it's moving, it becomes liquid. When it's in a rollerball refill, the movement of the ball applies some shearing force to the ink, turning it liquid, so it can flow out easily. On contact with the paper, it becomes more solid. While it's not usually very quick-drying, it stays put quite well once it's there, and isn't as prone to bleeding into the paper as liquid inks.
One big advantage of gel ink is that it's pigmented - that means it can be much more permanent and resistant to things like water and light than liquid and ballpoint inks. It doesn't mean all gel inks are waterproof, but some are, and most will at least stay readable after a splash.
Another advantage of gel pens won't be loved by everyone, but will be loved a lot by some people. The thick gel ink can hold more than just pigment - it can hold very fine glitter, or cosmetic glass, for sparkly writing. And who doesn't need a bit more sparkle in their life? Because pigments are opaque, they can also write in pastel colours that can show up on dark paper.
The problem gel ink brings, which liquid ink doesn't suffer from, is that it needs a reasonably consistent pressure to work. If you vary the pressure when you're writing, light pressure can skip, missing bits out; and heavy pressure can 'tramline' - leaving a gap down the middle of the line. For most people, it's not much of a problem, but it can be troublesome for others - especially those used to writing with pens that require no pressure at all to write with. The same feature means you can't get much variation from a gel pen - the line is either there or not, without the variation that can give liquid-ink rollerball and ballpoint writing some character.
Fountain Pen Ink
Ink that's safe to be used in fountain pens has to be fairly mild. It's usually a mixture of dye and water, not too strong on the dye, and with a few extra ingredients to make it flow well. Although they're mostly very similar in ingredients, small changes can make them behave more differently than you might expect, so there are plenty of people who love trying different fountain pen inks, seeing how each behaves in different pens, and how they work on different types of paper.
Fountain pens use a feed to get the ink from the reservoir inside (most commonly a cartridge or converter) to the nib. The feed is usually a piece of very carefully shaped black plastic, with narrow channels for the ink to flow through. Any ink that could dry out in the feed can be risky for fountain pens. That could, technically, apply to almost anything except pure water, but in practice, a dye-based ink that's not too saturated (too much dye) is pretty safe. Inks with pigment would tend to clog the feed up quite quickly, and things like calligraphy inks with shellac would be very likely to kill a fountain pen quite permanently.
Any ink that's made for use in fountain pens should be reasonably safe. Some specialist inks, though, are considered more risky, and should be treated with some extra care. A few brands make pigmented inks with very finely-ground particles, which are safe to use in fountain pens, but they're still much riskier than 'normal' fountain pen inks.
Almost any ink could be used for calligraphy, but inks sold as 'calligraphy ink' are usually pigmented for good solid colour, and formulated to work well on dip nibs. They're usually too thick to work well in fountain pens, and would be very risky to use in one, as they'd clog the feed. Some contain shellac, or similar ingredients, to give some extra shine to the finish, while some are metallic.
Iron Gall Ink
Also often known as Registrar's Ink, as it's commonly used by registrars for official records of births, marriages and deaths. It's common for the registrar to require that their own ink is used for signing the marriage registry, so it's done with iron gall ink. Outside this specialist use, it's quite a niche product, but is often of interest to people who are, well, interested in ink!
Traditionally made with galls from oak trees, it's iron in the ink that oxidises in the air that gives it its distinctive characteristics. The ink is most commonly blue, but darkens on the paper as it dries, and continues to darken further with time. Once it's darkened on the paper, it's permanent, and very difficult to remove.
Iron gall inks have a couple of drawbacks, though. One is that they contain tiny particles, making them a bit of a risk for fountain pens. The other is that they're somewhat acidic. While the acidity shouldn't be a problem for gold nibs, it can eat away at steel nibs, and other metal parts in a pen. Most modern iron gall inks aren't very acidic, and modern steel is more resistant to acids, so the combination isn't too dangerous, but it's safer to use iron gall ink in a pen you don't care too much about!
The interesting point this raises is that people who want 'archival' inks always look for 'acid free' ink and paper, while at the same time, registrars who absolutely need long term permanence from their inks use inks that are known to be acidic. Doesn't it eat away at the paper? Well, yes, to some extent, and there are many old documents where the iron gall ink used has eaten away the paper, but it takes a long time. It's generally more important to registrars that this type of ink has been proven to last long enough and to be permanent enough over many centuries of use. They're not about to jump to something that claims to be better, but has only been used for a decade - it's just not proven enough for them.
Diamine still produce a traditional iron gall ink they call Registrar's Ink, and there are other iron gall inks made for more 'normal' fountain pen users. Platinum's Classic Ink made something of a splash (do you see what we did there?) in recent times by giving us a range of iron gall inks in unusual colours, with varying degrees of colour changing as they dry. Despite the extra risks, they can be quite practical for everyday use, as these inks tend not to bleed through paper as much as most fountain pen ink, so they can actually work very well on cheap paper, or the paper used in many notebooks.
There have been many different approaches to erasable ink over the years. Those of us of the right age group will remember erasable ballpoints, which weren't very nice to write with, and didn't erase all that well either - but they seemed like a reasonably good idea at the time.
There have been a couple of attempts over the years at producing the 'liquid-lead pencil' - something very similar to a ballpoint, but where the colour in the ink is graphite, just like a pencil. They haven't caught on well enough to stick around so far, but we may well see them again.
In a subtle twist, some fountain pen inks are 'eradicable' or 'washable'. It's not quite the same thing as erasable, but they can be removed with an ink eradicator pen - a felt-tipped pen filled with a very mild bleach. You can't write over the top of the 'erased' bit with the fountain pen, because the ink would vanish on the paper, but the ink eradicator pens often have a fine blue felt tip on the other end, which can be used to re-write over the top.
The newest thing in erasable inks (at the time of writing, at least!) is thermal reactive inks, started by the very successful Pilot Frixion. Essentially, they change colour with temperature, but the colour they change to is clear. Make the ink become clear when it gets warm enough, and rubbing it with plastic can be enough for the friction to warm the ink up and change it. The change is quite clean, and the result is usually quite well erased, at least good enough for most uses; and the inks can be very nice to write with. The upshot is a nice gel pen that can be cleanly erased with an everlasting eraser on the end.
They do, of course, bring their own problems. Leaving your notes in a hot car, for example, can make them hot enough to disappear, which has been a distressing experience for some students. The original writing can be brought back by getting it cold enough - the freezer should do the job. The downside of that is that if your notes ever get cold enough, all the erased parts will come back. Between these effects, you shouldn't use these notes for anything where it's important your writing isn't erased, or where it's important that something you do erase stays erased.
Inks for Other Purposes
From the point of view of a bunch of pen geeks (hello!) one of the most interesting things about printing press ink is that it led directly to the invention of the ballpoint pen, as mentioned above. The ink has to be thick so it can stick to the lettering on the press, and needs to dry quickly, because once they get going, a printing press doesn't want to sit around waiting for the ink to dry before it moves on!
These days, a lot of printing is done with soy ink, made from soybean oil. It's more biodegradable than petroleum-based printing inks, and makes recycling easier and cheaper to do. It can also print brighter colours, but has a disadvantage - it's slower to dry, so printing presses have to be modified or run more slowly.
Inkjet printer ink is perhaps one of the most controversial types of ink around, mainly because it's so expensive, selling for anything up to £1,500 per litre. There are reasons that go well beyond the ink, though, as the 'packaging' has to include a complex ink feed system, and may also include the inkjet print head itself. Most inkjet printers are sold at or even below cost, too, with the manufacturers making the money later on the ink. All that is a long way from pens, though - nobody we can think of sells fountain pens below cost, then charges high prices for special cartridges that can't be refilled!
Interestingly, if you've heard the term 'Giclée' referring to fine art printing, it doesn't have any defined meaning beyond inkjet printing. It's usually used for high quality fine-art grade printing with archival quality inks, and a good professional inkjet printer is capable of very high quality results, so it doesn't usually mean the artist or photographer has just printed it on their home inkjet - but it's no guarantee they haven't!
Inks have had all sorts of important tasks to do in keeping our societies running. They gave us written laws, written contracts and written records. We may use a pencil to mark our 'X' on the ballot paper here in the UK (though we can also use ink), but the ballots themselves are printed with ink. Quite a few countries use ink in another way as part of their voting process.
Election ink is a special ink, usually purple, that stains skin very strongly. In countries where it's used, part of the voting process involves dipping a specific finger into the election ink, staining it purple for long enough that the voting process will be over before it could be removed. It's a simple way to prevent double voting. If your finger is purple, you've already voted, and you can't vote again. It probably adds a bit of peer pressure to the voting process. You can't tell people at work that you voted if you didn't - unless you find another way to turn your finger purple!
Tattoo ink is generally pigmented, and similar to other types of pigment inks. It's surprisingly lightly regulated, probably because problems are reasonably rare. Fineliners and plastic-tipped technical drawing pens are often used for drawing the design on the skin before use, and while they're certainly not certified or intended for such use, we've heard of tattoo artists using standard drawing inks.
To get away from potential predators, a cephalopod can squirt ink out into the water, making it difficult for the predator to see while it swims away rapidly. Squid ink is usually blue-black, while the octopus tends to produce a more pure black ink, and cuttlefish ink is brown. In fact, 'sepia', commonly used as a term for brown inks, comes from the Greek word for cuttlefish.
Toner, the 'ink' used in laser printers and copiers is mainly very fine particles of plastic, which the printer transfers to the paper, then uses heat to melt the particles so they fuse to the paper - the reason your printing comes out feeling all cosy and warm. But is toner a type of ink? That's debatable. It's used in laser printers for the same job as ink in most printing. It isn't a liquid, though it's such a fine powder that it behaves very much like a liquid. So it's arguable. We'll go with 'no', then we don't have to talk about it in an article on ink.
Choosing Your Ink
You want a pen, but what sort of ink should it use? It depends entirely on your preferences - there's no one type of ink that's just best.
If you vary your pressure when writing, gel ink won't work well for you. Stick to ballpoint or liquid-ink pens.
If you want to write on all sorts of paper, ballpoint is probably safest - there aren't many paper types made that don't work well with ballpoint pens.
If smoothness of writing is important to you, liquid or gel ink is best - ballpoints usually feel a bit more rough. If other aspects of ballpoints appeal to you, though, try a hybrid ink, which can combine the best features of both.
If you want some line variation, where the line width varies with your pressure, fountain pens and liquid-ink rollerballs are good, but gel ink won't suit you. Don't ignore the humble ballpoint, though - some amazingly expressive art can be made with ballpoint pens, as they give finer and paler lines with lighter pressure.
If you want the opposite - a very predictable line width - a gel pen could be ideal.
If you're concerned about the environment, and throwing away plastic, there are a few options. Any pen that's refillable will help, though many refills are plastic. A fountain pen could be ideal, as most can use bottled ink, which can avoid binning plastics entirely.
There are many different styles of calligraphy, and many different pens and other tools can be used. If you're using dip nibs, you'll find calligraphy ink works better than ink made for fountain pens, but there's nothing to stop you experimenting with all sorts of different inks. The same goes for applying ink with brushes - calligraphy ink and drawing ink would be ideal, but a brush can work with almost any type of ink, so have fun playing and seeing what works best for you!
For some styles, the Pilot Parallel Pen is king, and while it's really a fountain pen, so you should be careful about the inks you use, many calligraphers treat their Parallel Pens terribly, using calligraphy and drawing inks, and even watercolour paints in them. Generally, they get away with it, especially when only dipping the pen, or transferring ink to the nib with a brush, and the transition effects as the pen moves from one ink to another can make some amazing lettering.
You're asking the wrong people. We're a pen shop.
There are way too many different styles and techniques to really advise under a general heading of art! We can try to give a few suggestions for specific scenarios, though…
For 'line and wash' work, where you're going to sketch in ink, then add a bit of colour over the top, you'll want a pigmented drawing ink, so the lines don't wash away. Even with good pigment ink, though, test a little on the paper you're using first - some combinations may leave ink sitting on the surface that will wash out with water.
Drawing Japanese manga-style? Copic's alcohol-based markers are the best known option for colouring, and while most drawing pens will work fine, their MultiLiner pens are ideal. There are lots of Japanese brush pens, though, which can be perfect for this style. A lot of manga is done with dip pens, using G nibs for flexibility and Maru nibs for very fine lines.
Doing finely detailed work? A few drawing pens have sizes going down as far as 0.05mm, while some have 0.03mm tips too, all with pigmented liquid ink.
For art with ink in general, brushes and dip nibs are great tools, because they can be used with almost any ink. Using a fountain pen is very convenient, but it does limit the types of ink you can safely use. Dip nibs and brushes and use almost anything, and are quick to change inks with too.
Get silly! We've seen some great artwork and calligraphy done by dipping all sorts of things into ink, from fruit and vegetables to bits of litter found on the beach.
For many kinds of art, drawing and sketching, drawing pens are ideal - well, the name is a bit of a clue, isn't it? Generally, they're plastic-tipped, use pigmented liquid ink, and have a range of different tip sizes. Technical pens with metal tips are a bit more specialist, so you probably know if you need those. They also use pigmented liquid ink, and draw very accurate line widths.
You don't really get to choose the ink - it just comes with your cephalopod. If you want a nice sepia ink, make sure you choose a cuttlefish rather than a squid.
Fountain Pen Ink
One of the most appealing things about using a fountain pen is the variety of inks on offer. If your pen can use bottled ink, and most can with the addition of a converter, your options are almost unlimited. With cartridges, you may be a bit more restricted, depending on the pen. Some use a specific type of cartridges for the brand, where others use standard 'international' cartridges, which leave your options a bit more open.
So where do you start with choosing a fountain pen ink? There are so many of them! Fortunately, it's hard to go too far wrong - any ink sold as fountain pen ink should work fine in any fountain pen, though you may find some suit you or your pen better than others. Part of the fun of fountain pens is experimenting with inks, so if you just want something that works, almost anything will be good - just pick a brand and a colour - and if you want to play a bit more, dive right in!
Once you've decided what you're looking for, how do you find an ink to suit? While we try to be helpful in our listings, we'd have to say the best way is looking for reviews. Sites like Fountain Pen Network have forums full of ink reviews, with an amazing amount of detail, and you can search for discussions of inks with the features you want. That said, there's a lot of fun to be had in just trying ones that take your fancy, and seeing how they work for you.
Some factors you may want to consider:
There are fountain pen inks in almost any colour you can imagine, so whatever colours you love, you should be able to find something pretty close. Start with brands like Diamine and Robert Oster, who have huge ranges of colours, and the chances are you'll see what you're looking for.
We said anything sold as fountain pen ink should be good to use in any fountain pen, and that's true, but it's also fair to say that it's possible for any ink to dry out in the pen and clog the feed. Some are at a higher risk than others, and a few need some extra care. If any reasonably 'normal' fountain pen ink dries out in your pen, a quick flush through with water should sort things out again, or even just filling it again and using it may well work. Inks that are very strongly coloured, usually referred to as being 'highly saturated' will tend to be a little more risky. Reds and oranges are more likely to be troublesome than blues and blacks. And then there are specialist inks.
Generally, it'll be clear from the description or name if an ink is actually risky. There are inks like Platinum Carbon Ink with is a pigmented ink, rather than dye-based, and is more likely to clog the pen if it dries out. It's still fairly safe, but you don't want to leave it in an unused pen for weeks. Also from Platinum, the Classic range are iron gall inks - slightly acidic and with iron particles - again a bit more risky, but fine to use with a little bit of care.
Don't let any of this worry you too much. If you're buying weird inks, though, you might want to use them in a pen that's not too valuable. The risks aren't really too high, though, and if an ink does cause trouble, a flush through with tap water will usually put things right again.
Wetness and Flow
Fountain pen ink is a liquid, so it seems a bit silly to be talking about how wet it is, but here we are. Some inks flow more easily than others, and us pen geeks generally refer to it as the 'wetness' of the ink. An ink which flows well is wet, while an in that tends to flow less is dry. It's because a dry ink will give you a dryer line on the paper, while a wet ink will make, well, a wet line, which will take longer to dry.
Now we're starting to confuse ourselves.
If you want more ink on the paper, though, a wetter ink will help. If you want your scribbles to dry quickly, a dryer ink will do that.
Fountain pen inks are not usually permanent, depending on your definition. Most can be washed away with water, though some will wash away much easier than others. Look for reviews of a specific colour if you just want to make sure you'll still be able to read your notes after an accidental spill. If you're looking for something really permanent, there are options, but you should also consider other types of pen for this purpose.
Any fountain pen ink that is permanent, is also likely to be a bit more risky. As mentioned above, that doesn't mean it's unsafe to use, but there's likely to be a bit more risk. That said, we love Platinum's Carbon Black, with carbon nanoparticles, for a really good permanent black ink. And their Classic iron gall inks are wonderful fun if you like playing with unusual inks.
Although we don't currently stock them, we should mention Noodler's Ink here - especially the 'Eternal' or 'Bulletproof' range they're best known for. The founder, Nathan, does some amazing chemistry with inks, and the Eternal/Bulletproof inks react directly with the paper, making them (so far!) impossible to remove. They also seem to manage this while remaining (again, so far!) relatively safe to use. There are other special inks from Noodler's which aren't as safe, so some are probably still better avoided in a high-value pen, but the Eternal range is proving itself well.
Some inks do odd things.
Shading isn't uncommon at all, and most inks can shade to some extent. It just means that the ink is darker, or a more saturated colour, where more ink has been applied. In normal writing with a fountain pen, especially with a wet-writing nib, extra ink will 'pool' where the nib is lifted from the paper, leaving darker spots there, and lighter lines between. Some inks show this effect more than others. Some people love it, others hate it.
Sheening is more unusual, and harder to achieve for the ink maker, and the user. Some inks, when enough is laid down, have a sheen on the surface where they dry, in a different colour to the ink itself. In normal use, it can give little shiny contrasting edges around some parts of your writing, but only usually shows up on some types of paper.
Shimmering or glittery ink. Glitter in fountain pen ink shouldn't work - it should all just sink to the bottom, and it should clog up the pen's feed. But some manufacturers have found ways to do it. Diamine, Herbin and Robert Oster all make ink with tiny gold or silver particles, which give it a sparkle on paper. As you'd expect, there's a bit of extra risk to using these inks, but perhaps not as much risk as you'd expect.
We have a conclusion? Well, we should probably wrap this up somehow. How about this: Ink is fun!
Ink can have some very serious uses, silly uses and artistic uses. It's one of the most valuable tools for unleashing some creativity. You can use ink for writing your shopping list or a novel. For a quick sketch or a work of art you spend months on. It can write down a joke before you forget it, or be used for making laws. The stuff itself is pretty unassuming, but its possibilities are unlimited.