Dip pen
A dip pen is useful to most watercolorists, it is a good tool for fine lines and details. With a brush it’s hard to draw lines, but that’s what a dip pen is for. A good dip pen can create fairly long and even lines. It can also make flexible, different thickness lines with the right nib. It is a very useful tool which, however, should not be overused.
Nib Holder
A common type of holder is made of wood with a nib holder consisting of a metal ring and four metal tongues inside. The nib is clamped between the ring and the flexible metal tongues. Many of my students who have such a nib holder have just pressed the nib between the four tongues and thus destroyed the nib holder. It is not possible, or at least difficult, to change the nib if one were to do so. This type of holder is usually quite cheap, but personally I dislike them. They rust, are difficult to change nibs in. It is not possible to wash the holder without it cracking and becoming ugly and unusable over time.
Personally, I prefer the Japanese type of holder with a rubber mount for two types of nibs. A slightly wider ring for bowl-shaped nibs and a smaller ring for round nibs. The downside of the holder is that you have to buy a nib that fits, but most do fit.
There are also other types of nib holders, all are good in their own way: Nib Holders with metal tongues do not cost much, the Japanese ones are more expensive but more durable, easier to change the nib, and sometimes more comfortable. But it’s still just a nib holder, any will do, (although the Japanese ones are my favourite).
The nib
For the watercolor painter, it is fine lines that you use dip pen for. So therefore you should buy a nib with a fine tip, for me, as thin a tip as possible is what matters. I prefer nibs of the G model. G nibs are reasonably flexible and at the same time allow for really narrow lines.
A newly purchased nib is provided with a thin film of oil which should prevent the metal from oxidizing and becoming stained and ugly. This oil must be removed before the nib can be used. There are several different ways to remove the oil: some use toothpaste and a toothbrush, others dish soap. There are those who stick the nib into a potato and let it sit like that for a few minutes. Others wash with acetone.
Personally, I prefer to burn off the oil over a flame for a few seconds, no longer, as otherwise the nib may bend and become unusable.
Watercolor paint in dip pen
When you use a dip pen in a watercolor painting, you naturally want watercolor paint in the pen. With ink it’s easy, dip the pen in ink and write or draw. But watercolor paint is mixed in a small mixing cup that hardly has any depth, it is impossible to get color up with a dip pen from such a mixing cup.
Here’s how I do it: Pick up paint with a brush, transfer the paint to the pen held upside down. Drag the color towards the edge of the side of the pen, turn the pen over and draw. However, the color does not last very long, you have to redo the movement quite often if you are going to draw a lot. But for just a line or two, it’s a workable method.
Dip pen is also a good tool for masking fluid. You can use it when you need to save small details or thin lines. Of course, it is also possible to color a drawing made with dip pen with watercolor paint.